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Online KL27x

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #50 on: September 11, 2019, 10:26:29 pm »
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Going from my own experience, this is a vast improvement over my previous Antex based soldering iron usage where I now no longer have to agonise over whether to switch the Antex off to save wear on its tip and heating element whilst it roasts itself to an early demise keeping a soldering iron holder nice and toasty in between soldering activity when I spend the next "10 to 15 minutes" prepping the next lot of joints to be soldered which typically takes a lot longer than anticipated, or else switch it off and risk the need to solder another joint or two just after it has cooled down and be forced to allow it more time than it really needs to get back up to its unregulated soldering temperature. I reckon my irons have spent more than 90% of their on time just idling away in the iron holder, literally burning themselves up for no productive purpose.

 Being able to stop worrying about leaving an iron running hot and idle is the main bonus I'm getting with this soldering station. The temperature control and almost threefold power rating over my 25W Antex is the icing on this particular cake for me. :)
This is one way to skin a cat. If you are soldering heavy boards that require high set temps, this soldering paradigm is probably practical. Pick up iron, few seconds to warm up out of sleep, solder a joint, set the iron back down. And the T12 is certainly good at coming out of sleep, quickly. I think my T12 clones would be better at this than an 888. If this is you, this is a good iron and a step up from the old stuff.

The reason why the the 888 is simply better than my T12 clones, for me, is that most of what I solder I can do at temps low enough to not bother with sleep; not that I like to admit it, but I can and have left my iron on all night and started soldering the next day without even cleaning the tip, first. The 888 might not have as much power, but it has tighter temp regulation, so it can solder at a lower set temp. Probably 10-25C. And when I do production soldering, this is not just one joint then put the iron down. It's soldering scores of joints in succession for minutes at a time, so a lower set temp matters more than being fast out of sleep. Most hobbyists probably just need the tip to get plenty hot for a short spell, intermittently, and a bit hotter of a set temp doesn't really make a difference.

The burn-in. I agree it sounds like the KSGER possibly does a more aggressive compensation for an inherent con of the T12 tips (the sensor is directly coupled to the heater; not desirable). Might have to test it.
« Last Edit: September 11, 2019, 11:02:51 pm by KL27x »
 
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Online bd139

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #51 on: September 11, 2019, 10:34:00 pm »
Just chipping in here. I am convinced the T12's are a piece of shit. I've had two and I was not impressed. When they work they are pretty good but the whole ecosystem is tuned to failure. Firstly the isolation and safety arrangements in them are somewhere between absolutely dire and murderous. Literally the mains connector is lap soldered onto the case. Earth is just WTF. Secondly the quality is very poor. The handpiece on mine was so poorly engineered, the tip shorted out at the contact level and blew the crap out of the controller. Thirdly the stand situation is terrible. It's like that scene in Men In Black where they're sitting in the chairs trying to write stuff. Absolute piece of crap. I actually took mine in the garden and hurled the bastard onto the roof of my neighbour's garage where it lives to this day.

This is something they could fix with quality control but I suspect they are designed for the home market where keeping costs down trading off safety is the win. I'm not getting into the KSGER vs Quicko vs X vs Y thing; they are much of a muchness.

As mentioned earlier, buy once. I bought the ass end Metcal PS900 and the thing is manna from heaven. You can solder tits onto a snake with it.

If that's too pricey it has to be a genuine Hakko. I was put off by the poor supply chain in the UK for their stuff so opted to go pricey.

Also lets not forget the "manky old Weller TCP" which is obtainable on ebay for less than half a Hakko at average, all the parts are still available and it'll be there after world war three armageddon with the cockroaches and my mother-in-law.
« Last Edit: September 11, 2019, 10:37:50 pm by bd139 »
 

Offline Johnny B Good

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #52 on: September 14, 2019, 05:27:24 am »
Quote
Going from my own experience, this is a vast improvement over my previous Antex based soldering iron usage where I now no longer have to agonise over whether to switch the Antex off to save wear on its tip and heating element whilst it roasts itself to an early demise keeping a soldering iron holder nice and toasty in between soldering activity when I spend the next "10 to 15 minutes" prepping the next lot of joints to be soldered which typically takes a lot longer than anticipated, or else switch it off and risk the need to solder another joint or two just after it has cooled down and be forced to allow it more time than it really needs to get back up to its unregulated soldering temperature. I reckon my irons have spent more than 90% of their on time just idling away in the iron holder, literally burning themselves up for no productive purpose.

 Being able to stop worrying about leaving an iron running hot and idle is the main bonus I'm getting with this soldering station. The temperature control and almost threefold power rating over my 25W Antex is the icing on this particular cake for me. :)
This is one way to skin a cat. If you are soldering heavy boards that require high set temps, this soldering paradigm is probably practical. Pick up iron, few seconds to warm up out of sleep, solder a joint, set the iron back down. And the T12 is certainly good at coming out of sleep, quickly. I think my T12 clones would be better at this than an 888. If this is you, this is a good iron and a step up from the old stuff.

 This is me right enough! :)  I've been examining this whole business of using thermocouple sensing for temperature regulation of soldering iron tips over the past few days (hence the delay in replying to this post).

 It turns out that this clever way to sense actual tip temperatures is riddled with several practical limitations over and above that of simply maintaining a tight coupling between 'cause and effect' in these cartridge styled soldering tips where the heating element and the thermocouple sensor are integrated as closely as possible to "the business end" of the tip in order to minimise the errors caused by thermal lag and temperature gradients.

 These modern electronic control systems were designed to offer more flexibility of temperature control over that of the earlier Curie point temperature stabilisation method which had relied on the user having to choose from a selection of tips with a temperature setting that had been defined during their manufacture.

 It turns out, the task of getting such a "direct drive" thermocouple based control system to perform well is a lot more complex than the thermostatically controlled immersion heater model would suggest as I've recently been finding out.
 
The reason why the the 888 is simply better than my T12 clones, for me, is that most of what I solder I can do at temps low enough to not bother with sleep; not that I like to admit it, but I can and have left my iron on all night and started soldering the next day without even cleaning the tip, first. The 888 might not have as much power, but it has tighter temp regulation, so it can solder at a lower set temp. Probably 10-25C. And when I do production soldering, this is not just one joint then put the iron down. It's soldering scores of joints in succession for minutes at a time, so a lower set temp matters more than being fast out of sleep. Most hobbyists probably just need the tip to get plenty hot for a short spell, intermittently, and a bit hotter of a set temp doesn't really make a difference.

 Actually, as one of the things I've been finding out, the excess power rating of these thermocouple controlled tips is mostly to provide a rapid warm up and fast response against the cooling effect of soldering small to medium thermal masses typically encountered on PCBs.

 For the very first time ever, I used my Daniu FG-100 clone tip thermometer to check the tip temperature on my 25 year old Antex XS25 230vac mains soldering iron to see how hot it manages to get when left in the iron holder for more than quarter of an hour. It took some two or three minutes just to get up to 300 deg btw and some 15 minutes later it had topped out at 426 deg. I suspect, given another half hour it would probably have ultimately reached 430 deg with its 25 watt heating element warming a bit that approximates the T12-BC3 that I've currently gotten burnt in with the KSGER controller.

 Checking the average percentage figure, now that the BC3 tip has stabilised at 450 deg and above temperatures, I see 7% at 300 deg and 14% at 430 deg when it's parked in the holder. Assuming a 100% figure equates to 72 watts, the resulting 5 and 10 watts drive power seems in line with the Antex's use of 25 watts to drive a tip with just over double the effective surface area of the BC3 tip in a T12-9501 handle.

 One significant observation I've noted (prompted by this whole business of "tip burn in") is that once a stabilised tip has been set to the maximum of 480 degrees, the percentage of power, after the initial burst of accelerated heating at 100% for the first second or so, it soon drops down long before it gets to within 50 degrees of the target temperature to just 15%. Hitting the 50 deg boost, the percentage reading dances between 0 and 45 deg suggesting an average heating power of just 15 to 16 watt being applied to achieve an "indicated" temperature of 530deg from a 72 watt rated tip.

 I used quote marks around that "530 deg" figure because it's what the controller believes it's seeing from a tip that's never managed to top 470 deg, according to my tip thermometer (which I have suspicions of in regard of its (apparent) lack of cold end temperature compensation - more of that anon). What I suspect the problem is with tip temperature stability in this case is the use of a 24.5v supply with a controller designed to work over the 12 to 25 volt range where the optimum voltage would be around the 20 volt mark (optimum balance between control and stability of temperature).

 The clue to this lies in the default (5S lipo battery's worth - the smpsu voltage corresponds to a 6S Lipo pack) alarm voltage of 18.5 and cut off voltage of 18.2 (from memory - I forgot to take note before exploring the full voltage ranges and I'm not going to reset it back just to find out). You can dial these voltage settings right down to 6 volts and as high as 28 volts in spite of the absolute maximum voltage rating figure being only 26 volts. Of course, with this unit currently being mains powered, this function remains disabled.

 This capability to use rechargeable battery packs of any chemistry without undue risk of reverse charged cell damage from over-discharging the battery is a very handy feature of the control module and you might think the 12.6 volts from a freshly charged car battery would provide too little power into an 8 ohm heating element (I've got a 16/18 watt Antex that would suggest otherwise) but for soldering low thermal mass joints, it's actually more than sufficient if you can tolerate the more protracted warm up time.

 Going by its behaviour in seemingly avoiding 100% power other than for very brief bursts once you go over the 450 degree setting (who needs a 450 deg setting anyway?), I suspect the PID control algorithm has been designed to eliminate the risk of the heating element/thermocouple burning out. These direct drive tips with their 8 ohm heating elements may take 72 watts off a 24 volt supply but I suspect they wouldn't survive this treatment for very long. It seems to me more a figure of merit with regard to accelerated heating up performance and response to thermally demanding solder joints.

 The choice of a 24.5 volt smpsu over a 21 vot smpsu seems to have been made purely to create impressively quick heating up times with scant regard to stability. Looked at more closely, I suspect a simple voltage reducing mod to the existing smpsu board to drop the voltage will become all the rage with these soldering stations (once I've figured out where to solder in the extra resistor, whether a fixed or switched option - perhaps using an internal jumper  >:D).

 I might reduce its existing "getting up to temperature" performance from "Hell! That was bloody fast!" to just "That was quick!" but I'd expect much better temperature control at the lower voltage. Reducing the heating power from 72 down to 52 watts won't impact its soldering performance very much when the "at 450 deg temperature" power input is being throttled back to just 20% of the full 72 watt rating of the tip anyway.

 The wattage figures quoted by the big brand named manufacturers for their direct drive tips are almost certainly attention grabbing headline figures anyway so I think exploring the lower voltage options will lead to a better balance between performance and usability.
 
The burn-in. I agree it sounds like the KSGER possibly does a more aggressive compensation for an inherent con of the T12 tips (the sensor is directly coupled to the heater; not desirable). Might have to test it.

 The heating element is made with nichrome (chromel) which is one of the metal alloys used to construct a K type thermocouple so all that is required to turn the heating element circuit into a K type thermocouple is to use alumel as the return conductor. Unfortunately, the 41μV per K difference between the hot and cold junctions is not produced at the hot junction but is the result of the imbalance of the thermoelectric effect along each conductor as a result of the different metal alloys used for each of the two wires which connect the hot and cold junctions.

 This means that the voltage produced will essentially be an indicator of the heating element temperature rather than what is happening right at the hot junction by the tip. For more info, you can do what I did (Cheat - I'm no thermocouple genius!) and look at the wikipedia article here:- https://en.wikipedia.org/wiki/Thermocouple#Type_K

 Cunningly disguising your thermocouple as a heating element might seem undesirable but perhaps not quite for the reasons you might have thought. As long as you can afford to shut off the heating current for long enough to sample the thermocouple voltage (the 8 ohm resistance in one leg of the circuit won't matter when detecting a voltage with a relatively high impedance circuit - in this case 10KR or higher should be high enough), say a millisecond or two every 100 to 200 or more milliseconds, there shouldn't be any problem monitoring heater/tip temperature this way other than for the inconvenient fact that it is the temperature of the heating element rather than that of the actual business end of the tip that's being monitored in the pious hope that, through the high thermal conductivity of the metal used to conduct this heat  the actual tip temperature won't be lagging too far behind. ::)

[The above statement in regard of the thermocouple only measuring the heater temperatures is actually a misconception on my part - Apologies for this and please check out my explanation in the edit at the end of this article]

 If you read the whole of that wikipedia article, you'll see mention of the ageing effect which means our cartridge tips will eventually start to under-report their temperature, causing them to run a little hotter as a result of the controller trying to maintain the reported temperature. The calibration feature is more than just "A nice touch", it's more a necessity if you don't want to eventually end up frying your delicates (smds).

 As for the required accuracy, it's just as well that there's some considerable leaway in soldering temperatures. The choice of just sufficient temperature with a longer dwell time versus the higher temperature with a shorter dwell time to avoid overheating the components is a "Damned if you do, damned if you don't." kind of choice. Low temperature reduces oxidisation and flux boil off rates but risks higher component temperatures whilst "Hot 'n' Quick" risks burnt tips and flash boiled flux if the task is fumbled. The experienced solderer soon adapts to the best balance between these two extremes - thankfully there's a lot of latitude to work within.

 Talking of accuracy (and referring back to a comment I made earlier), I bought a cheap clone of the Hakko FG-100 tip thermometer to allow me to calibrate my collection of T12 tips. Since the original Hakko and clones alike all use a K type thermocouple with its characteristic 41μV per K output, a cheap clone tip thermometer needn't be any less accurate than an over-priced Hakko 'original' (at least in principle) but I'm having some doubts as to how it (or even whether it) implements some form of 'cold junction compensation'. Since it's a clone of the Hakko unit, it does beg the question as to whether genuine Hakkos will behave in exactly the same way as mine did.

 Mine, a Daniu branded clone, seems to track the room temperature to within a tenth or two of a degree of my weather station's ambient temperature readings (and that of the KSGER's cold end temperature in sleep mode which was calibrated to the weather station's reading to begin with - just an extra data point).

 On the face of it, it would seem to have some form of cold junction compensation but when I took it outside to see if it would match (or at least track) my outside thermometers and weather station's remote sensor, I saw some rather wild variations of temperature (ranging some 5 to 10 degrees higher than expected) which bore no obvious linkage to the outside conditions. Next, I thought I'd see just how cold our chest freezer really was. Incredibly, it never registered below zero deg C other than to offer a fleeting glimpse of the minus sign on a zero deg reading.

 At that point I'd refitted the thermocouple the wrong way round, thinking it had some aversion to indicating temperatures below zero and then I started seeing the reading go up to 27 deg (minus, obviously) but when I took it out and allowed it to warm back up, instead of sticking on zero as it passed that point, it started showing minus readings before I decided to refit the thermocouple the right way round to make sure it would return to a sane ambient reading which it eventually did after warming it over the toaster to some 70 deg to accelerate evaporation of the condensation it had accumulated on being removed from the freezer.

 In spite of that abuse, it now reads the room temperature just as it did before, somehow giving the impression that it does have some form of cold junction compensation that works when it's sat on a bench in a room that varies from a low of 19 to a high of 24 deg C. If anyone is intrigued enough by these results to repeat any of my tests, would you be so kind as to please let me know what you find? :)

 What's bugging me the most about this is that I can't figure out any circuit configuration or limitation due to bad design that could account for all this weirdness. If anyone's got any ideas of their own on this, I'd appreciate any sort of insight that might clear up this mystery. Trying to second guess someone else's design mistakes when you can't reverse engineer just what they've done wrong can be an exercise in futility if you "Haven't seen it all." I only know how it's supposed to work, not how many inventive ways there may be to make it fail so weirdly.  :-//

JBG


[EDIT 13:25 BST 15 Sep 2019]

 Inspired by that wikipedia article and the exorbitant price of even the cheapest of replacement thermocouples for these soldering iron tip thermometers (they're a 'consumable' where  'cheapness rises to the top of the list of desirable 'properties'), I started looking for "DIY Thermocouple" articles during the reading of which, I suddenly had an epithany.

 Whilst it is true that the voltage produced between the hot and cold junctions is a consequence of the Seebeck effect over the whole length of the thermocouple wires joining the hot and cold junctions, this doesn't alter the fact that the voltage produced is still due to the difference in temperature between each of the junctions even when the conductors pass through a region at a higher temperature than the 'hot junction'. The reason of course, being that it's only the net temperature difference between the hot and the cold reference junctions that matters.

 Excursions of temperature along the wires joining the two junctions beyond that of each junction simply cancel themselves out in the net temperature difference equation that informs us of the temperature at the hot end junction compared to that at the cold end junction.

 What this means is that it remains possible to place our hot junction close to the 'business end' (perhaps right at the 'business end' by drilling a short gallery into the core of the copper bit into which the hot junction can be placed) and essentially ignore the higher temperature on the thermocouple wires obliged to pass through the much higher temperature region of the heating element.

 Of course, practical limitations in the placement of the hot junction means the effect of the thermal gradient between the heater and the tip will compromise the goal of sensing the tip's actual temperature to a greater or lesser extent depending on the details of the design of our self sensing direct drive cartridge tip. It's not too difficult to see where clone tips might fall short of the originals.
« Last Edit: September 15, 2019, 01:47:49 pm by Johnny B Good »
 

Online KL27x

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #53 on: September 14, 2019, 06:21:54 am »
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Cunningly disguising your thermocouple as a heating element might seem undesirable but perhaps not quite for the reasons you might have thought. As long as you can afford to shut off the heating current for long enough to sample the thermocouple voltage (the 8 ohm resistance in one leg of the circuit won't matter when detecting a voltage with a relatively high impedance circuit - in this case 10KR or higher should be high enough), say a millisecond or two every 100 to 200 or more milliseconds, there shouldn't be any problem monitoring heater/tip temperature this way other than for the inconvenient fact that it is the temperature of the heating element rather than that of the actual business end of the tip that's being monitored in the pious hope that, through the high thermal conductivity of the metal used to conduct this heat  the actual tip temperature won't be lagging too far behind. ::)
But there is a problem. When the heater is on, a temp gradient will develop between the heater/sensor and the copper slug at the base of the tip. The heater will reach higher temperatures than the surrounding copper ever will; and the sensor is directly coupled to the heater. So when the power is on full blast, and it is temporarily cut to take a reading, it will measure higher than when the heater has been off for longer and the temp of the sensor is actually closer to that of the surrounding copper. Despite the copper could be the same exact temp in either case.

In the 888, the sensor is thermally insulated from the heater. The sensor is measuring the temperature radiating from the inside of the tip. For the heater to affect the sensor, it has to heat the tip; then the tip heats the sensor.

Quote
that once a stabilised tip has been set to the maximum of 480 degrees, the percentage of power, after the initial burst of accelerated heating at 100% for the first second or so, it soon drops down long before it gets to within 50 degrees of the target temperature to just 15%.
Both my clones exhibit this behavior at all set temps. They throttle down well before reaching set temp and only slowly coast to full set temp WHEN UNDER NO THERMAL LOAD. When under load, they sag, significantly.* I believe it to be the natural side effect of the thermal coupling between sensor and heater. Maybe there are clones with more sophisticated sensor compensation.

*Yes, all irons exhibit temperature drop/gradient between the base of the tip where the sensor is and the point that is on the joint. But apples to apples, similar 3mm bevel tip on either, the T12 clones I have exhibit an additional sag compared to the lower power 888, which I suspect is due to the sensor/heater thermal coupling.

The "less overshoot" is bullshit on these clones. Any overshoot on an 888 is minimal. And when it does happen, it's temporary. The T12 clones have to be set to a significantly higher set temp to overcome the thermal sag, and they spend a lot of time at this significantly higher set temp while doing production type soldering. The overshoot of an 888 is much preferable to this situation. These T12 clones basically have way more "undershoot" than the overshoot of an 888.

The T12 clones (which I have) are excellent for a hobbyist that wants a fast warm up time and for anyone who needs to run such high temps anyhow that standby is essential. And cartridge tips are excellent for sustaining high load/output without warming up the handpiece. But they do not regulate better/tighter.

Quote
The heating element is made with nichrome (chromel)
Yeah, if you say so, I'll roll with it. W/e it is, it's just one of many stainless steel alloys that is used for heating wire. Like other stainless steels it is a poor conductor of heat compared to non-stainless steels/irons. And even cast iron is a poor conductor of heat compared to copper. Add the fact that the heater wire must be electrically insulated from the copper, and that it's tightly coiled up in a relatively small volume rather than spread throughout the copper,*** and that is why a rather significant temp gradient will occur when the heater is active. Heater gets hotter than the copper; sensor is directly connected to the heater; hence what the sensor measures is affected by other variable than just the temp of the copper at the base of the tip. Your signal has a skew to it, which is an interesting challenge to fix through software. It is especially interesting since the user of the iron represents an unknown, unpredictable variable to the thermal load on the tip, and that load will also increase the amount of sag in this loop. In addition to the sensor being connected/coupled to the heater and being affected by heater activity, the T12 heater needs to have a certain amount of mass to do its job, and the thermocouple needs a certain minimum mass to transmit the power without heating itself up. The ideal sensor for this, say like the one in an 888, would have a super high surface area to mass ratio, with very minimal mass, since it only needs to be a variable resistor to a very low voltage and current signal.

***I imagine the heater is a relatively small and compact length of coiled nichrome that is tucked into a hole in the back of the copper tip-slug with a dab of thermal cement, based on the price point these are made to.
« Last Edit: September 14, 2019, 09:37:49 am by KL27x »
 

Offline jadew

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #54 on: September 14, 2019, 09:37:37 am »
Quote
that once a stabilised tip has been set to the maximum of 480 degrees, the percentage of power, after the initial burst of accelerated heating at 100% for the first second or so, it soon drops down long before it gets to within 50 degrees of the target temperature to just 15%.
Both my clones exhibit this behavior at all set temps. They throttle down well before reaching set temp and only slowly coast to full set temp WHEN UNDER NO THERMAL LOAD. When under load, they sag, significantly.* I believe it to be the natural side effect of the thermal coupling between sensor and heater. Maybe there are clones with more sophisticated sensor compensation.

That is standard behaviour for any PID controller that's correctly tuned, and should behave roughly the same with or without a load. The 888 should behave similarly, with the added downside that because of the thermal lag, it will have poor transient response. It will be both slower to get to temp and it will have more overshoot when removing the load, as well as taking more time to figure out it's loosing temperature when applying a load.

No matter how you look at it, delay in a PID controller is bad and it will yield poorer results.

Edit: Generally speaking, when you have lag in the response you have to compromise between slow and overshoot. The smaller the lag is, the smaller the compromise.
« Last Edit: September 14, 2019, 09:41:23 am by jadew »
 

Online KL27x

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #55 on: September 14, 2019, 09:48:38 am »
Quote
That is standard behaviour for any PID controller that's correctly tuned,
It is beyond that, though.
edit: If you sink heat out of the tip, the base of the tip will also sag in temperature, not just the pointy end. The circuit only powers the heater with a small portion of the available duty cycle. It has bumped the power some, but not as much as it should. The base of the tip sags in temperature from the set point, and the circuit doesn't do anything to amend this problem. It accepts it. This is the new normal/equilibrium.

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and should behave roughly the same with or without a load.

You are not speaking anything I can make sense of. I have explained already in the previous post. T12 sensor/heater has mass. Tip under load means it is something is sinking heat out of it. Copper transmits that quickly. But it takes a bit for the sensor to change, because it has lower heat conductivity and has some significant mass. 888 is superior in this regard.

Quote
The 888 should behave similarly,
But it does not. The heater is switched by a triac, and there is no PWM. There is an indicator LED (7 segment decimal point) that lights up when the heater is switched on. (And it is accurate; scoped it some 2-3 years ago; when the dot is lit, the heater is receiving full power). The 888 does not behave like this, and anyone who owns one can easily attest. It doesn't need to, because the thermal mass of the tip is large enough, the power is low enough, and the sensor response is exceptionally fast by design. There is additionally no lag in the heating. That is not a weak link; there's no shortage of electricity to make more heat. So what if the 888 heater must (very quickly) reach higher temp:surface area to drive same wattage into the tip as the T12 heater? The only weak link of the 888 is the leakage of heat into the rest of the handpiece.

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with the added downside that because of the thermal lag, it will have poor transient response. It will be both slower to get to temp and it will have more overshoot when removing the load, as well as taking more time to figure out it's loosing temperature when applying a load.
I will agree to disagree. :-//

Edit: A really good PID should be able to give closer to all or nothing on the gas when it's still tens of degrees off. The better performing PID would give 100%, shut off power, completely, and coast up to the correct temp, and then resume the exact right itty bitty duty cycle to keep it right there just as it is peaking. It wouldn't start going 30% or less when it's still 50C low. And it wouldn't allow a greater thermal load to result in a falsely high temp reading, triggering sag.

Quote
Edit: Generally speaking, when you have lag in the response you have to compromise between slow and overshoot. The smaller the lag is, the smaller the compromise.
You assume the 888 sensor significantly lags behind when the tip changes temp, and that this is a weak point in the system. What makes you think that? You make assertions without showing how you got there.

If you drill a hole into a copper block and insert a temp sensor, then stuff some asbestos insulation to plug the hole, the temp of that sensor is going to stay very close to the temp of the copper block no matter what you do.  Put that block in your oven and turn it on, and your sensor will faithfully report the temperature of the block of copper. There will be a little lag, due to thermal mass of the sensor and heat conductivity/transfer. But if you designed it right, it is going to be fine and not any concern compared to the rate of delta you can expect for the block in your application. That's a hakko 888.

Now instead of putting it in an oven, take the heater coil out of your oven and crumple it up into a ball, and stick it in the hole with the sensor. Turn on the "oven" and warm the block up to 300F. Your sensor got fried to a crisp in the interim, because the heater reached, say, over 1100F in order to do this. And after you turn it off, that coil remains hotter for a discrete amount of time, due to its thermal mass. So given you can read the temp of the sensor, now figure out how hot is the copper block... How to do that conversion? Well, you can try to make some sort of correction based on past history leading up to this point, but that reading is simply inaccurate at first. And it gains in meaning the longer you let the heater cool and gain equilibrium to the surrounding copper.




One of my T12 clones has no microcontroller. The control circuit is fairly simple. There's a 1 shot that powers the heater, and there's a comparator that fires this one shot. When the comparator says go, heater is powered for a spell. After that set amount of time, it returns to sensing and waiting for the sensor to drop in temp enough to trigger the next dose of on-time. The natural result is that the power is pretty close to 100% only for the first 5 seconds when first turning the station on. Once it has gotten in the neighborhood of set temp, you will never get the heater over a 50% duty cycle again, even if you dunk the tip in a glass of water. The delay before retriggering starts to grow well before the tip reaches temp, since the heater is reaching higher temp than set temp by this point. This has nothing to do with fancy PID. It's just a dual opamp circuit.

So the temp rapidly rises at first. But it slows down way too early. And it limps to the set point with the duty cycles ever decreasing. When you apply a heatsink to the tip to siphon off some wattage, the duty cycle creeps back up just a little. The circuit happily allows sag and stabilizes at a lower temp of the base of the tip. The circuit simply waits for the temperature of that sensor to drop to X (as set by the knob) before it fires the next dose, and because of the discrete amount of time it takes for the sensor to cool back down from just being roasted, there is your lag. The T12 setup is the one with the lag.

Even under no-load equilibrium at full set temp, where the heater is on a low duty cycle just to maintain temp in ambient air, the sensor data includes an offset for the differential between (hotter) sensor and (cooler) base-of-tip. When under increasing sink from contact with a joint, this point will get reached prematurely, because the differential between the sensor and the base-of-tip has gotten larger by way of higher duty cycle to the heater AND faster cooling of the tip by the heatsink. Both of these things increase the error in the reading. So the offset for the set-point at no-load is no longer big enough to correct for the current conditions.

Going from undertemp joint to the next, the recovery is also throttled back to a crawl for no reason other than artifact of heater/sensor design. It is a temp controlled station, but the temperature control is compromised and partially hamstrung.

My other T12 "Bakon" has an AVR microcontroller. It might have fancy PID, but it performed just as poorly (actually a bit worse) in controlled test with temperature probe regarding sag.

The thermal lag in an 888 causes it to oscillate in a sawtooth, once it reaches equilibrium. In a T12 clone, this sawtooth is almost completely gone. But it means the temp stabilizes at ever lower sag point under load, much greater drop and problem in practice than the sawtooth of the 888 in equilibrium. This is in the T12 clones I have; maybe yours has 200% more magic beans. And even of the ones I have, for some persons for some purposes, the advantages will be enough to not care about this area of absolutely worse performance. For me, the advantages of the T12 cartridge are not enough, and I still await the knowledge of which T12 clone (or genuine 951, for that matter) has the magic bean PID that can better correct for the sensor/heater compromise without creating new compromises.

It is very easy and straightforward to comparison test the amount of sag from set point between irons, using an iron temperature tester and a test PCB. No need to theorize and guess based on your own (possibly incomplete; I'm not exempting myself, mind you) understanding of thermodynamics and marketing wankery and shoulda woulda coulda. All you have to do is test it. It's not subjective. It doesn't matter why one performs better than the other. You don't have to understand or reason it through, even if you're capable. All you have to do is test it, because in the end we are talking about the performance of a soldering iron.

And at least put some eyeballs on it (e.g. you could scope your T12 clone's output FET to see its behavior*) and process it for a second, before you declare "this" to be "standard behaviour for any PID controller that's correctly tuned." It is fairly obvious that if you compare this to standard thermostatic behavior, or to optimized PID, this is neither one nor the other, nor is it anywhere between; it's clearly on the wrong side of what you would call an "improvement." If this behavior is created, intentionally, it's the result of a series of terrible decisions...

... or maybe you would find that your T12 station does not perform the way I have described mine.

*it might help to either fiddle with the timebase of your scope to make it slow enough to plot pwm as an average voltage and/or to connect an R-C low pass filter and measure the voltage on the capacitor, if all you have is a DMM.
« Last Edit: September 15, 2019, 11:12:09 pm by KL27x »
 
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Offline Johnny B Good

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #56 on: September 16, 2019, 01:08:06 am »
Quote
Cunningly disguising your thermocouple as a heating element might seem undesirable but perhaps not quite for the reasons you might have thought. As long as you can afford to shut off the heating current for long enough to sample the thermocouple voltage (the 8 ohm resistance in one leg of the circuit won't matter when detecting a voltage with a relatively high impedance circuit - in this case 10KR or higher should be high enough), say a millisecond or two every 100 to 200 or more milliseconds, there shouldn't be any problem monitoring heater/tip temperature this way other than for the inconvenient fact that it is the temperature of the heating element rather than that of the actual business end of the tip that's being monitored in the pious hope that, through the high thermal conductivity of the metal used to conduct this heat  the actual tip temperature won't be lagging too far behind. ::)

But there is a problem. When the heater is on, a temp gradient will develop between the heater/sensor and the copper slug at the base of the tip. The heater will reach higher temperatures than the surrounding copper ever will; and the sensor is directly coupled to the heater. So when the power is on full blast, and it is temporarily cut to take a reading, it will measure higher than when the heater has been off for longer and the temp of the sensor is actually closer to that of the surrounding copper. Despite the copper could be the same exact temp in either case.

In the 888, the sensor is thermally insulated from the heater. The sensor is measuring the temperature radiating from the inside of the tip. For the heater to affect the sensor, it has to heat the tip; then the tip heats the sensor.

Quote
that once a stabilised tip has been set to the maximum of 480 degrees, the percentage of power, after the initial burst of accelerated heating at 100% for the first second or so, it soon drops down long before it gets to within 50 degrees of the target temperature to just 15%.

Both my clones exhibit this behavior at all set temps. They throttle down well before reaching set temp and only slowly coast to full set temp WHEN UNDER NO THERMAL LOAD. When under load, they sag, significantly.* I believe it to be the natural side effect of the thermal coupling between sensor and heater. Maybe there are clones with more sophisticated sensor compensation.

*Yes, all irons exhibit temperature drop/gradient between the base of the tip where the sensor is and the point that is on the joint. But apples to apples, similar 3mm bevel tip on either, the T12 clones I have exhibit an additional sag compared to the lower power 888, which I suspect is due to the sensor/heater thermal coupling.

The "less overshoot" is bullshit on these clones. Any overshoot on an 888 is minimal. And when it does happen, it's temporary. The T12 clones have to be set to a significantly higher set temp to overcome the thermal sag, and they spend a lot of time at this significantly higher set temp while doing production type soldering. The overshoot of an 888 is much preferable to this situation. These T12 clones basically have way more "undershoot" than the overshoot of an 888.

The T12 clones (which I have) are excellent for a hobbyist that wants a fast warm up time and for anyone who needs to run such high temps anyhow that standby is essential. And cartridge tips are excellent for sustaining high load/output without warming up the handpiece. But they do not regulate better/tighter.

Quote
The heating element is made with nichrome (chromel)

Yeah, if you say so, I'll roll with it. W/e it is, it's just one of many stainless steel alloys that is used for heating wire. Like other stainless steels it is a poor conductor of heat compared to non-stainless steels/irons. And even cast iron is a poor conductor of heat compared to copper. Add the fact that the heater wire must be electrically insulated from the copper, and that it's tightly coiled up in a relatively small volume rather than spread throughout the copper,*** and that is why a rather significant temp gradient will occur when the heater is active. Heater gets hotter than the copper; sensor is directly connected to the heater; hence what the sensor measures is affected by other variable than just the temp of the copper at the base of the tip. Your signal has a skew to it, which is an interesting challenge to fix through software. It is especially interesting since the user of the iron represents an unknown, unpredictable variable to the thermal load on the tip, and that load will also increase the amount of sag in this loop. In addition to the sensor being connected/coupled to the heater and being affected by heater activity, the T12 heater needs to have a certain amount of mass to do its job, and the thermocouple needs a certain minimum mass to transmit the power without heating itself up. The ideal sensor for this, say like the one in an 888, would have a super high surface area to mass ratio, with very minimal mass, since it only needs to be a variable resistor to a very low voltage and current signal.

***I imagine the heater is a relatively small and compact length of coiled nichrome that is tucked into a hole in the back of the copper tip-slug with a dab of thermal cement, based on the price point these are made to.


 I'm a little ashamed to say that the posting you're responding to contained a major misconception on my part. I've since edited that post to correct this but I'll paste that edit here to clarify the situation.

[EDIT of Reply #52 13:25 BST 15 Sep 2019]

 Inspired by that wikipedia article and the exorbitant price of even the cheapest of replacement thermocouples for these soldering iron tip thermometers (they're a 'consumable' where  'cheapness rises to the top of the list of desirable 'properties'), I started looking for "DIY Thermocouple" articles during the reading of which, I suddenly had an epithany.

 Whilst it is true that the voltage produced between the hot and cold junctions is a consequence of the Seebeck effect over the whole length of the thermocouple wires joining the hot and cold junctions, this doesn't alter the fact that the voltage produced is still due to the difference in temperature between each of the junctions even when the conductors pass through a region at a higher temperature than the 'hot junction'. The reason of course, being that it's only the net temperature difference between the hot and the cold reference junctions that matters.

 Excursions of temperature along the wires joining the two junctions beyond that of each junction simply cancel themselves out in the net temperature difference equation that informs us of the temperature at the hot end junction compared to that at the cold end junction.

 What this means is that it remains possible to place our hot junction close to the 'business end' (perhaps right at the 'business end' by drilling a short gallery into the core of the copper bit into which the hot junction can be placed) and essentially ignore the higher temperature on the thermocouple wires obliged to pass through the much higher temperature region of the heating element.

 Of course, practical limitations in the placement of the hot junction means the effect of the thermal gradient between the heater and the tip will compromise the goal of sensing the tip's actual temperature to a greater or lesser extent depending on the details of the design of our self sensing direct drive cartridge tip. It's not too difficult to see where clone tips might fall short of the originals.
[/EDIT]

 You seemed in doubt about the use of nichrome (chromel which is one of the alloys used both in heating elements as well as one half of a K type thermocouple) for the heating element in the Hakko (and cloned) T12 cartridge tips but it makes perfect sense to choose this particular alloy since it then becomes a simple matter to convert it into a K type thermocouple by welding the top end connection close to or within the copper tip to its partner alloy, alumel, for the return conductor.

 Rather neatly, Hakko have created a dual function all in one heating element/K type thermocouple, where each function is just a matter of time sharing with a PID controller. My misconception of the thermocouple so formed only being able to read the heater element temperature simply doesn't apply. It is no less capable of sensing the hot end temperature than a thermocouple connected via a separate dedicated circuit to the controller (other than for some slight heat leakage along the chromel heating wire leading from the coiled chromel wire which makes up the bulk of the heating element - a factor also present to a lesser extent in the separate thermocouple case since its wires are likewise forced to pass through the heated region).

 No doubt, the PID control algorithms can be fine tuned in both cases to take account of this effect, leaving little to choose between the dedicated and dual function sensing options. In the end, it all comes down to the details of the cartridge tip design and that of the controllers and the sophistication of their PID control algorithms which, going by my own experience with the KSGER version 2.10 firmware, still has some way to go in its development.

 As for my idea of reducing the drive voltage by a few volts to tame the KSGER T12 controller's behaviour, I'm having second thoughts about expending any further time and energy in pursuing such a strategy. As I've already stated, I can't see much benefit in using temperatures above 350 deg C for soldering in general, particularly as I don't intend to use lead free solder in any of my projects.

 Since stability and performance seem perfectly ok in the more sane soldering temperature ranges below 350 deg, there seems little need to try a reduced voltage option. In any case, on those rare occasions where I might need more heat output to solder sheet metalwork such as creating shielding boxes from tin plate or copper clad board, I'm sure the controller will respond much better in those cases of heat demand when the tip has to be kept in contact with such heavy duty thermal sinks.

 Since I've never had experience with any soldering tools other than the half century old sleeve bit technological innovation made by Antex (now refined in the Hakko T12 cartridge tips) and just lately, a brief experience with the KSGER T12 soldering station, I see no point in arguing against your case for the Hakko 888 soldering station kit's superiority over that of the FX-951 and these cheap Chinese upstarts designed for use with T12 tips.

 However, we do seem to be in agreement regarding these KSGER T12 soldering stations being a very cost effective upgrade from the basic soldering iron when it comes to hobbyist use (ignoring the issues of electrical safety and poor workmanship in the assembly of the handles).

 Quite frankly, these cheap soldering stations based on the T12 tip technology represent a leap forward on a par with that of Antex's electrically heated sleeve bit technology over that of the old fashioned gas heated poker irons that preceded even the crappy electrically heated versions of those old fashioned poker irons (Solon Irons, anyone?).

 They may lack the level of power and temperature stability of professional kit designed for production soldering such as Pace and JBC but they more than make up for this with a rich feature set more suited to the hobbyist's typical 'hit and run' pattern of use, even outdoing the Hakko FX-951 soldering station in this respect (I watched the following review video to refresh my memory of the FX-951)



 It was a competently done review but I did notice a serious error in regard of the T15 (T12 tips for most of us purchasing via Ebay and Amazon) when showing the circuit of the tip connections. The two ring connections are the only connection to the heater/thermocouple circuit. The sleeve contact, which was shown as a common connection point for separate heater and thermocouple circuits, is totally isolated from the heater circuit, the function of which is solely to provide an ESD safety earth contact.

 After my experience of the KSGER soldering station, what struck me most about the FX-951 setup was it's needless complexity in sensing the idle time through the use of a 'special' soldering iron holder with its gravity operated micro-switch requiring all the paraphernalia of a stereo cabled link using 3.5mm jack and sockets at each end and a feature poor user interface requiring a pathetic plastic key to minimise interference with its "key settings" (pun unavoidable) by cow-orkers in a factory floor setting.

 I did notice that the startup timings from cold (and from the needlessly high 200 deg C standby temperature), though still respectfully fast, were a little bit more protracted than the KSGER unit's timings (but we all know the price of such speed - stability issues at temperatures above 350 deg C and the need to "deflower" virgin tips).

 Referring back to the question posed by this thread's title, I'm very much of the opinion that the KSGER T12 soldering station is a better alternative than going for an all original Hakko setup with it's needless complication, cumbersome UI and higher price even when purchased secondhand. This cheap Chinese alternative does have the virtue of being based on the Hakko T12 (T15) cartridge tips (whether fakes, KSGER clones or original Hakko) which provides a range of 85 or more tip shapes to suit every conceivable need (perceived or otherwise).

 The only major downsides that I can see with these cheap Chinese made units are the safety issues in the 24v smpsu boards used in most variants of this T12 soldering station and the quality of the workmanship in the handles, all of which are amenable to uncomplicated DIY re-working by almost every hobbyist blessed (or cursed) with even the most rudimentary of soldering skills. As such, I certainly couldn't recommend them as a first time soldering iron purchase to a novice electronics enthusiast going beyond the solderless breadboarding stage of their hobby for the very first time.

 However, I would recommend these soldering stations to anyone running a class in basic practical electronics as an excellent repair or (for the kit versions) build project for such novices to take away at the completion of the course. It could either be in the form of basic coursework materials stock paid for out of tuition fees or else at the top of a "recommended buys" list of self provided materials not to be plugged into a mains socket without the supervision of the tutor to verify that it would safe to do so.

 I know we should be discouraging such shoddy disregard for electrical safety (and to a less urgent extent, quality of assembly) by refusing such cheap Chinese death tr... bargains but this is the real world and there seems to be an inexhaustible supply of cash strapped hobbyists lacking the essential life skill often referred to as "Cynicism" (millennials) all too willing to part with their hard earned 'at any price', so that laudable "Refuse to buy" action just ain't gonna fly.

 The way I see it, such Chinese cheapies represent a way for me to monetise (in a round about way) my electronics skills by converting such danger ridden cheap and shoddy kit into cheap kit that I could otherwise not afford to own. In times past, I've used my skills merely to convert shoddy expensive kit into expensive kit worthy of its expense.

 This time round, the difference now, courtesy of China's disregard for electrical safety, is the added sense of danger you get when receiving such goods from the likes of Banggood and chums. Plugging such Chinese cheapies straight into a wall socket unchecked after unboxing them is a game I call "Chinese Roulette". It's similar to Russian Roulette only without the loud bang and smoke of a revolver and with much longer odds than the one in six chance of being the loser in the traditional game.

 Whilst the extruded aluminium cased KSGER T12 soldering stations all seem to be cursed by the dangerous smpsu board issue (the tatty plastic cased units seem to use a safer design of 24v 3A smpsu board) and the build quality of the handles supplied/available for this series of soldering stations is rather questionable, I don't see why this alone should deter anyone in this group, looking to satisfy a hobbyist usage requirement, from buying one.

 The faults are trivial to remedy by anyone with a modicum of DIY electronics repair skill in possession of a basic 25 watt soldering iron and a 180 watt or so rated soldering gun or equivalent (requirements which I believe should easily be met by almost everyone reading this sage advice of mine here  ;)  ). Suggesting that such defects are reason alone to recommend against its purchase to the membership of the eevblog forums would, I feel, be an insult to the group's intelligence, especially so for the ever resourceful hobbyist looking for a cost effective way to upgrade and expand their existing soldering toolkit.

 Mention of the "Cash strapped Hobbyist" case, it's possible to build one from the many parts available for even less money than I paid for my ready built unit. If you already have a 20 to 24 volt dc 3A rated power supply or a 4S to 6S liPo battery pack (with charger) to hand and a suitable enclosure to build it into, you can buy the 3 digit LED versions for as little as six or seven quid and save a ton of cash. I think the OLED versions were around the 18 quid mark the last time I looked

 However, having checked out Banggood, Ebay and Amazon, they don't appear to be quite so prolific as they once were and looking at what is available, I get the impression that this is older stock with all the "Good Stuff" having been hoovered up. I believe there were issues with these early versions burning out their analogue 3.3v regulator when powered from 24 volt supplies (the later models used a dc-dc converter to get round this issue) so this might not be quite as good an idea after all. In the end, it might be better simply to buy a ready built unit like this one https://www.banggood.com/KSGER-V2_1S-T12-Digital-Temperature-Controller-Soldering-Station-Soldering-Iron-Tips-T12-K-p-1338117.html?cur_warehouse=CN  for which I paid £39.05 last month.

 It's currently at £38.39 right now (it had been dropped to just under 30 quid just over a week ago for maybe a whole week) so what its price might be in a few days time is anyone's guess. Internet shopping has never been easy at the best of times IME and Banggood's trampoline pricing doesn't make this task any easier. As far as I can see, that particular item still represents the best bang for the buck as well as the best combination of accessories, not just on Banggood but also everywhere else I've searched.

 These can be bought in kit form but they're often way more expensive this way. I even saw a kit of this model for 37 quid and some change that included everything except a PSU board!  :wtf: Also, if you're new to buying from Banggood make sure you don't pick the dearer warehouse option by force of the habit that the CN option is always cheaper. This isn't always the case as I found out to my cost when I ordered a Mustool G600 Digital 1-600X 3.6MP 4.3inch HD LCD Display microscope for a couple of quid more than the UK warehouse option price which would have also allowed me to take earlier delivery as opposed to my still having to wait for it to arrive a week after placing the order.

 If anyone is tempted to try out one these cheap soldering stations, good luck in securing one at the right price and don't forget to check out all those youtube review and teardown videos if you haven't already bingewatched them like a good boy scout (always be prepared!).

JBG
 

Online KL27x

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #57 on: September 16, 2019, 10:04:50 am »
Quote
What this means is that it remains possible to place our hot junction close to the 'business end' (perhaps right at the 'business end' by drilling a short gallery into the core of the copper bit into which the hot junction can be placed) and essentially ignore the higher temperature on the thermocouple wires obliged to pass through the much higher temperature region of the heating element.
This is a nice idea. But even if you move the hot junction away from the main section of heater, the hot junction still needs to be large enough gauge to transmit power. And it still needs to be electrically insulated from the surrounding copper. So in otherwords, it takes up space. Space that could otherwise be filled in with copper. I think the front of the tip is better served to be solid copper than to hollow it out for this type of sensor.

I might have some spare tips to cut in half. Another day, perhaps.
 

Offline scatterandfocus

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #58 on: September 16, 2019, 06:17:18 pm »
The Edsyn 971 (used) finally showed up today.  It seems ok.  I think it will be fine for my uses, although I definitely wouldn't buy one of these new at a $300 price for hobby use.

I like the pod iron holder.  It holds the iron well, and it opens up  to change out what looks like a wax paper insert for catching solder drips.

The iron feels ok.  The cable for the iron is about 40".  The iron is hardwired.  The tip that came with it is a small chisel tip, maybe 1.5MM, which will be good for my uses for now.

The station has a 'Heater Cycle' LED.  The way that it seems to work is that when no heating is taking place the LED is off.  When it is getting up to the set temp, the LED is solid.  When it begins regulating the temp, the LED flashes quickly.  And it seems that when it reaches full temp, the LED flashes slowly.

Using the temp probe on my DMM, it seems to take around a minute to to go from a beginning temp of 32C to a setting of 700F/371C, but the temp on my meter is showing around 350C at that point.  I'll have to play around with it a bit more to see if I can get better temp measurements from my meter and see how much the temp drops when doing big joints.
« Last Edit: September 16, 2019, 06:26:35 pm by scatterandfocus »
 

Online KL27x

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #59 on: September 16, 2019, 06:26:25 pm »
Quote
When it begins regulating the temp
It's always regulating temp from the moment you turn it on.  ;D
Quote
the LED flashes quickly
Curiously, the LED/heater of an 888 never flashes quickly. Idiots think this is necessarily an indication that this indicates delay in response compared to an iron that flashes nonstop. That is one theoretical explanation, but in this case it is because the 888 has an accurate sensor with a very high signal to noise ratio.

In case of the Edsyn having moments where it does this super fast/fuzzy blinking, I suspect some leakage/coupling between heater to the sensor, honestly, and/or more noise, less signal. Quick flashing is not necessarily indication of awesome, high tech stuff happening.
« Last Edit: September 16, 2019, 06:36:19 pm by KL27x »
 

Offline scatterandfocus

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #60 on: September 16, 2019, 06:30:59 pm »
Quote
When it begins regulating the temp
It's always regulating temp from the moment you turn it on.  ;D
Quote
the LED flashes quickly
Curiously, the LED/heater of an 888 never flashes quickly. Idiots think this is necessarily an indication that this indicates delay in response compared to an iron that flashes nonstop. That is one theoretical explanation, but in this case it is because the 888 has an accurate sensor with a very high signal to noise ratio.

In case of the Edsyn having moments where it does this, I suspect some leakage of heat from the heater to the sensor, honestly. Quick flashing is not necessarily indication of awesome stuff happening.

I played around with it a few times so far.  There is definitely quick flash and slow flash patterns, although I am not positive on what they mean.  The manual is very minimal in operation instructions.  It only says on the Heater Cycle LED:  Set desired temperature.  Blinking Lamp means Tool is regulating.  http://www.edsyn.com/mm5/graphics/00000001/971i.pdf

Also of note here, I tried sending Edsyn an email to ask some questions on iron tips, but my email domain was bounced (Tutanota).  So if I want to talk to anyone about it, I will have to call.
« Last Edit: September 16, 2019, 06:36:49 pm by scatterandfocus »
 

Online KL27x

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #61 on: September 16, 2019, 06:43:07 pm »
Unless there is some indicating going on with the fast blink (not related to the heater action, but Edsyn wanted to add some visual indication of some state), I think the manual is just feeding marketing level wank.
 

Offline Johnny B Good

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #62 on: September 16, 2019, 06:48:00 pm »
Quote
What this means is that it remains possible to place our hot junction close to the 'business end' (perhaps right at the 'business end' by drilling a short gallery into the core of the copper bit into which the hot junction can be placed) and essentially ignore the higher temperature on the thermocouple wires obliged to pass through the much higher temperature region of the heating element.
This is a nice idea. But even if you move the hot junction away from the main section of heater, the hot junction still needs to be large enough gauge to transmit power. And it still needs to be electrically insulated from the surrounding copper. So in otherwords, it takes up space. Space that could otherwise be filled in with copper. I think the front of the tip is better served to be solid copper than to hollow it out for this type of sensor.

I might have some spare tips to cut in half. Another day, perhaps.

 Damn it! You just spotted the snag in my thoughts on trying to place the thermocouple closer to the tip!  :(

 I have the feeling that I may be overthinking this issue of sensor/heater placement. Looking at the tip construction of the irons used by the Hakko 888D stations, it looks like the thermocouple must simply be embedded right at the end of the exposed ceramic heater element, presumably with a few millimetres separation from the end of the heater section so it seems these irons have a similar issue to the T12 cartridge tips regardless of whether the thermocouple is on its own circuit (perhaps sharing a common low resistance return wire).

 Practically speaking, there seems no obvious way to avoid sensing the temperature somewhere along the thermal gradient betwixt tip and heater (hopefully, a point closer to the tip than to the heater). I can imagine that a very sophisticated PID control algorithm could make allowances for this less than ideal situation, taking into account predetermined temperatures versus the averaged amount of power being delivered to the heater, it's effect on the thermal gradient, taking into account thermal lag and so on but it looks like a very complex solution that could still be knocked out of kilter by slightly unusual soldering conditions.

 Chaos theory looks likely to be The Lord Murphy's choice of weapon here in confounding the soldering station manufacturers' best efforts if they go for a complex PID control algorithm solution. Perhaps I'm overthinking things yet again. :-//

 I notice a lot is being made over the virtues of 'direct drive' versus the fixed heater with interchangeable sleeve tips setup. Undoubtedly, cartridge tips have an advantage but not because they offer better heat transfer from heater element into the tip than the older, Antex styled sleeve tips but mainly because they can concentrate the heat into a lower thermal mass tip for a faster response to the thermocouple sensor feedback to the controller. Reducing heat leakage back into the handle is a nice bonus feature but the basic 25W Antex isn't troubled by excess heat leakage into the handle but that has double the grip to tip distance of a T12 tip in a 9501 handle to solve this minor issue.

 The myth of "Better heat transfer" from the heating element into the sleeve tip is what irritates my sensibilities the most with this argument. The plain fact is that it doesn't matter whether the thermal gradient between the tip and heating element is 150 deg C or 250 deg C just as long as the nichrome wire used in these elements stays comfortably below its melting point which it obviously does as demonstrated by all those ancient Solon 65W monstrosities with their remote heating section glowing red hot just to get a screw retained tip at its far end up to a working temperature of maybe 350 deg C on a hot day (without a following wind if you're lucky).

 Sure, some extra heat energy will go the wrong way but it's just a case of "Give it a longer handle and bump the heat up another five percent or so." The thermal gradient between heater and tip is not the big deal it's made out to be. That in itself is not the great advantage for the direct drive cartridge tips.

 The major advantage is in getting the heat source closer to the business end of the tip and in reducing the non- working area to minimise the "Space Heater" effect of the bulkier designs. It also helps reduce co-lateral damage and aids visibility around the solder joints being worked on in the more cramped space of the miniature world of SMD circuit boards (so much so that you need magnifying aids to see exactly what you're doing with the end of your pencil tipped iron).

 Of course, the reduced thermal mass places more reliance on the PID temperature control algorithm providing adequate compensation against the heat sapping effects of soldering activity. In this regard, I agree with your own assessment that overshoot is a more desirable departure from perfection than undershoot with this form of soldering temperature regulation.

 With regard to the thermal conductivity of copper, the following youtube video is an impressive demonstration of this although I did cringe a little over the use of a two tine fork arrangement where I'd have formed each side of the thick copper wire 'desoldering bit' into triangles to provide two thermal paths into each end of the bases being applied to the IC's pins.

JBG

« Last Edit: September 16, 2019, 07:08:57 pm by Johnny B Good »
 

Online Shock

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #63 on: September 16, 2019, 06:49:02 pm »
Scatterandfocus, from what you described the LED is showing heating. Solid while warming up, fast flashing then slow flashing then off, it all fits the narrative.
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Online KL27x

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #64 on: September 16, 2019, 06:55:08 pm »
Quote
I have the feeling that I may be overthinking this issue of sensor/heater placement. Looking at the tip construction of the irons used by the Hakko 888D stations, it looks like the thermocouple must simply be embedded right at the end of the exposed ceramic heater element, presumably with a few millimetres separation from the end of the heater section so it seems these irons have a similar issue to the T12 cartridge tips regardless of whether the thermocouple is on its own circuit (perhaps sharing a common low resistance return wire).
I disagree.

The sensor on an 888 is indeed at the tip of the ceramic stick. The heater is behind that. But this doesn't mean they are tightly coupled. The sensor and heater can be separated by thermal insulation/heat-shield. Maybe it's 3mm thick of insulation? Maybe it's less? It's still insulated way better than the T12 sensor. Provided there's sufficient insulation, the main thermal coupling between them besides the tip, itself, is the ceramic case and the air gap in the hole. The radiating heat from the inside of the tip can effectively swamp that out.

Take sensor; put it in a block of copper; plug the hole with asbestos. Now heat the block by shooting a torch right into the hole. The asbestos blocks that heat from transferring directly to the sensor.* It's the copper that the torch heats up. The copper distributes this heat very effectively. So the copper block acts like it's all the same temp. To heat up the area around the sensor, you have to heat the entire block.

edit: if you turn on an 888 with the tip off, the ceramic heater will glow and break (or maybe it is smart enough to detect a user error?). Because the sensor will never reach the set temp. When you remove the tip, you remove 99% of the thermal coupling.

If you removed the tip from the T12 heater/sensor and turned it on, it would cut back/kill the power sooner/earlier than normal.

*A good thermal insulator like asbestos basically can maintain a large temperature differential on either side of itself with minimal heat transfer/conduction. There's a limit. When that differential exceeds that amount, then the conduction occurs very quickly. Think of it as the VFD of a diode. As long as you are below the knee, conduction is minimal. When you exceed it by X, it's much like applying X directly across a good conductor. So the designer of this station just has to select the insulation and thickness that covers the worst case. This applies to the "horrible" air gap between heater and tip in an 888, as well. Someone who doesn't know physics might think this airgap necessitates a "lag" or "delay" in heat transmission. Once the differential is established (heater X degrees hotter than the air... Air is X degrees hotter than the copper...) the conduction occurs relatively unimpeded. There is no such "delay." What goes in one end comes out the other. If we also had to cool the tip from the heater end, then that would be a bigger problem. This stackup would cause slop in the lead screw when switching directions, and taking out that slack would require a discrete amount of time. But since we only have to heat it at one end, and 99.9% of the cooling (and only cooling) occurs at the other end, there is very little slop in the lead screw. And this is gone very soon after the heater turns on, and everything moves in lockstep.
« Last Edit: September 17, 2019, 03:24:55 am by KL27x »
 
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Offline scatterandfocus

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #65 on: September 16, 2019, 06:56:48 pm »
Unless there is some indicating going on with the fast blink (not related to the heater action, but Edsyn wanted to add some visual indication of some state), I think the manual is just feeding marketing level wank.

I just noticed that the flash pattern is variable, not 2 states.  The pattern seems to be fastest when getting up to temp and settles down to a slow pattern after reaching temp.  Sort of... It doesn't seem terribly well indicative of anything meaningful to me at this point.  I will treat the station like I treated the old Hakko 936 ESD.  Turn it on, wait a minute or so, tin the tip, and solder some joints.  And if I need to adjust the temp, twist the knob.  No menu fiddling.  What I am really curious about with this station is how well it will do for big joints, being that the heater is rated at 95 watts.
 

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #66 on: September 16, 2019, 07:18:02 pm »
Quote
The pattern seems to be fastest when getting up to temp and settles down to a slow pattern after reaching temp.
Weird.

888 is solid on until it hits set temp. Then it quickly settles into a distinct duty cycle for w/e load it is under, like clockwork. At 300C no load, it is a short blip every 2-3 seconds, maybe 4-5% "duty cycle" (although the period is not exactly constant, it is very close to being a metronome). Under a constant heatsink of some size, the heater will quickly settle into a regular rhythm, at a higher "duty cycle," again, like a frigging metronome. Except the "period" shortens, as expected, due to a higher rate of change (cooling) of the tip.

This is exactly the behavior you should expect in a thermostatically controlled iron that is operating with clean, accurate, responsive sensor information. For the exacting repeatability/consistency that is observed (demonstrating relatively high accuracy), the response time of an 888 is actually very incredible.

Not referring to scatterandfocus Edsyn odd behavior. But in general, if your iron heater flickers on/off super fast, that is either PWM or noise in the sensor or heater/sensor coupling. If the tip is still miles off from set temp, it is more full power. When it gets closer, it doesn't know the fuck to do at any given time and is either averaging out to be right (if it's purely noise) or it is sucking (if there is also underlying unresovlable error, say due to coupling). There is no way that it is representative of a "super fast response time," considering the size of the copper tip and the the power of the heater. That is wishful thinking and naievity. 

99% of people don't understand basic physics/thermodynamics enough to even apply known science and knowledge to a model like a soldering iron. Enter marketing wanketeers. They suggest stuff that "makes sense" to this average person. And that person says, "oh yeah, I knew that," and they automatically connect dots that don't connect. And forever more, they "know" stuff that is completely wrong. As long as the iron is soldering stuff 10 seconds after flipping the switch, they are completely happy and satisfied that all the other claims are 100% scientifically correct.
« Last Edit: September 17, 2019, 03:28:09 am by KL27x »
 
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Offline Johnny B Good

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #67 on: September 16, 2019, 10:58:00 pm »
Quote
I have the feeling that I may be overthinking this issue of sensor/heater placement. Looking at the tip construction of the irons used by the Hakko 888D stations, it looks like the thermocouple must simply be embedded right at the end of the exposed ceramic heater element, presumably with a few millimetres separation from the end of the heater section so it seems these irons have a similar issue to the T12 cartridge tips regardless of whether the thermocouple is on its own circuit (perhaps sharing a common low resistance return wire).
I disgree.

The sensor on an 888 is indeed at the tip of the ceramic stick. The heater is behind that. But this doesn't mean they are tightly coupled. The sensor and heater can be separated by thermal insulation/heat-shield. The only thermal coupling between them is the ceramic case and the air gap in the hole. The radiating heat from the inside of the tip can effectively swamp that out.

Take sensor put it in a block of copper plug the hole with asbestos. Now heat the block by shooting a torch right into the hole. The asbestos blocks that heat from transferring directly to the sensor. It's the copper that the torch heats up. The copper distributes this heat very effectively. So the copper block acts like it's all the same temp. To heat up the area around the sensor, you have to heat the entire block.

 Is there any reason then, why Hakko haven't used exactly the same method with their direct drive cartridge T12 and T15 tips (same tips, different market regions)? You say the irons used in the 888D system keep the heater and thermocouple circuits separate from each other as opposed to the T12 direct drive tip arrangement of making the heater act as a thermocouple on a time shared basis.

 I'm wondering whether the move to this combined heater and thermocouple two wire arrangement in the FX-951 system wasn't inspired by a need with the 888D to shut off the ac current to the heating element during thermocouple readings to eliminate interference to the thermocouple signal anyway - why use four (or at the very least, three) contacts when the cheaper option of just two will serve the purpose just as well?

 IIRC, the FX-951 still used 24vac via a triac switch to power the heating element so would be restricted in its timings (assuming a zero crossing thermostat switching algorithm) to the nearest half cycle of mains voltage (8.3333ms for 60Hz or 10ms for 50Hz) although it would be kinder to the transformer to choose whole cycle switching periods giving thermocouple measurement windows of time in multiples of 16.7 or 20 ms for the controller to grab its readings.

 Obviously, there'll be the new issue of self heating of the thermocouple junction from the heating current in this case which may require a longer refractory period than just a single cycle of mains voltage to reduce its impact. A tenth of a second may be sufficient to reduce this effect to a negligible enough level for the PID control algorithm to take this into account.

 The obvious downside is that the dropping of heating power five cycles at a time is going to bite into the power rating depending on how frequently the measurements need to be taken in order to maintain a satisfactory level of control. At the lower power demands required to stabilise tip temperature at, say, the 350 degree mark, a much longer refractory period can be used, say 900ms off with 100ms on (10% power), offering less self heating error for the controller to deal with.

 Higher temperatures will require shorter refractory periods, coupled with longer on periods, making the controller's task to achieve temperature stability much harder. I suspect this may well be the reason for the KSGER's high temperature behaviour and the apparent 470 deg "ceiling" on maximum tip temperature that I've witnessed so far.

 It could be that Hakko have addressed this self heating issue by using their own wire drawing machinery to manufacture their own heating coils where the last 10 or 15 mm going into the thermocouple junction is much thicker to create the best trade off against electrical self heating and the increased thermal conduction from the heater region of the wire which may explain and justify their much higher price compared to the fakes or clones lacking in such refinement.

 Investing in a genuine Hakko T15 tip may well prove worth while in being able to avoid the need to 'deflower' a virgin tip and enjoy better high temperature stability and performance. The only fly in this jar of ointment is the seemingly exorbitant price to run this experiment.

 BTW, I was being very specific about the T15 choice of tip simply because there's a reduced risk of being sold a fake tip if I take a chance on an Amazon/Ebay seller (Banggood's T12 tips are definitely fake or at best, KSGER clones) rather than play safe and order direct from Hakko or one of their accredited agents. For now, I'll see how I get on with the KSGER clone tips - the experience may make me only too happy to part with the money to get a genuine Hakko tip which is the best way, imo, to "pay extra" for "the real deal" (no nagging doubts about the need to spend big).

 Having just searched for a Hakko agent, the one and only uk agent I could find (I'm not going to give this Hakko agent any oxygen of publicity - you can do your own research) is asking £12.66 (+ vat = £15.19) for most of the more common T15 tips. You can pay a lot more for the more specialised tip options and for those that think the cheap FG-100 thermocouple thermometer for checking tip temperature was too cheap at just around the ten quid mark, you can always salve your conscience by spending some 186 quid (plus vat! :wtf:) on the 'real deal'. :-DD :-DD :-DD :-DD

 I have a very strong feeling it will be a very chilly day indeed in Hell before I buy a "Genuine Hakko" T12 or T15 tip. >:( >:( >:( >:(

JBG
 

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #68 on: September 16, 2019, 11:10:58 pm »
Quote
I'm wondering whether the move to this combined heater and thermocouple two wire arrangement in the FX-951 system wasn't inspired by a need with the 888D to shut off the ac current to the heating element during thermocouple readings to eliminate interference to the thermocouple signal anyway - why use four (or at the very least, three) contacts when the cheaper option of just two will serve the purpose just as well?

No. The 888 doesn't do this. And it doesn't need to do this. It doesn't cut power to take a reading. When the heater is on, it's 100% on, and it doesn't turn off until the sensor reading indicates it should. There's a zero crossing detector, but it is only used to switch the TRIAC on. The sensing/comparing is occurring continuously, nonstop (but how often the micro reads this, who knows? Maybe it is only reading in sync with the zero cross? Either way it's neither here, nor there. It works whether the heater is on or off just the same). The T12 uses a compromised arrangement for production/cost reasons, alone, I imagine. Although you can make an argument that fewer contacts increases reliability, since you're sliding a cartridge into a holder and powering/sensing through spring contacts.

Just for clarity, I am not 100% sure it's impossible for another clone (or genuine 951) to get accurate temperature readngs without needing excessive off periods of the heater to do so. I can't imagine the way you would do it without getting so deep/complex that the occasional mis-identification of current state creates a terrible error. Once the micro goes down the wrong rabbit hole, how long before it figures out north is actually south and what are the consequences? But I'm sure things are possible which I can't imagine.

The more info the station has the better. The 951 does not identify different tips, AFAIK, and some other cartridge systems have a way to transmit that information, so the station has at least that much more solid info to work off of.

Quote
Higher temperatures will require shorter refractory periods, coupled with longer on periods, making the controller's task to achieve temperature stability much harder. I suspect this may well be the reason for the KSGER's high temperature behaviour and the apparent 470 deg "ceiling" on maximum tip temperature that I've witnessed so far.
Yes, I agree that the higher the duty cycle, and the higher the heatsinking (the differential between 470C and ambient air > 350C and ambient air) the trickier it would be to get accurate temperature sensing. But FWIW, Hakko has set the limit of the 951 at 480C. I don't know how high the KSGER interface goes, but if it works reasonably well to 470C, that seems like it should be plenty hot. If you're at that temp to make solder joints, precise temp control probably doesn't matter, so long as the tip doesn't misregulate so bad it burns itself up. Anywhere near this temp, and you're smoking flux like mad, you're oxidizing any exposed iron plating like mad, and you're just gonna lift the iron when you see the joint flow. I mean, at this temp, you know you're not using the right tool for the job, already. Anytime you are using the thing only ever at 10 and wishing there was an 11... damn what a waste of engineering to make the thing adjustable to begin with. You might not be using the tool the way the designer imagined.
« Last Edit: September 17, 2019, 01:30:24 am by KL27x »
 

Offline Johnny B Good

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #69 on: September 17, 2019, 03:46:47 am »
Quote
I'm wondering whether the move to this combined heater and thermocouple two wire arrangement in the FX-951 system wasn't inspired by a need with the 888D to shut off the ac current to the heating element during thermocouple readings to eliminate interference to the thermocouple signal anyway - why use four (or at the very least, three) contacts when the cheaper option of just two will serve the purpose just as well?

No. The 888 doesn't do this. And it doesn't need to do this. It doesn't cut power to take a reading. When the heater is on, it's 100% on, and it doesn't turn off until the sensor reading indicates it should. There's a zero crossing detector, but it is only used to switch the TRIAC on. The sensing/comparing is occurring continuously, nonstop (but how often the micro reads this, who knows? Maybe it is only reading in sync with the zero cross? Either way it's neither here, nor there. It works whether the heater is on or off just the same). The T12 uses a compromised arrangement for production/cost reasons, alone, I imagine. Although you can make an argument that fewer contacts increases reliability, since you're sliding a cartridge into a holder and powering/sensing through spring contacts.

 That's interesting. I came across a thread in the dangerous projects forum describing something similar from 2013. The OP had designed a controller for use with the T12 tips where he described the use of a powerfet to switch the 24vac on and off for controlling the heater power, synced to the zero crossings, turning it off half a millisecond before it hit zero and turning it back on half a millisecond after to create a thermocouple voltage sensing window less than 1ms wide every half second or so to keep track of the temperature even during the on periods of the duty cycling of the heater's power level as well as monitoring during the off periods.

[EDIT 2019/09/21] Here's the link to that dangerous project's page http://dangerousprototypes.com/forum/index.php?topic=5264.0

 My first thought when I read that was that this was way too fast to avoid the self heating issue of the thermocouple junction but it would seem not to be quite the issue I supposed it to be. Once again, I seem to be overthinking this (in public! :-[ ) Overthinking things is ok given enough 'overthinking' time for all the facts to finally fall into place before offering them to all and sundry to pick to pieces.

 I think the issues I'm conjuring up do exist, just not quite to the troublesome level in practice that I imagine them to be in theory. One way I can imagine that the issue of self heating can be minimised is by using some sort of crimp to join the wires together which provides a larger area for the copper core of the tip to dominate the temperature of the junction and act as a heatsink for any self heating effect of the heater wire that makes up one half of the thermocouple junction.

 The crimp can be any suitable alloy just as long as it can maintain its integrity as a crimp with a healthy temperature margin beyond the upper limit of the maximum temperatures expected to be measured since it has no effect on the working of the thermocouple even when it provides the only electrical link between the wires rather than just squash them into direct contact with each other (another wikipedia fact! ;)).
 

Just for clarity, I am not 100% sure it's impossible for another clone (or genuine 951) to get accurate temperature readngs without needing excessive off periods of the heater to do so. I can't imagine the way you would do it without getting so deep/complex that the occasional mis-identification of current state creates a terrible error. Once the micro goes down the wrong rabbit hole, how long before it figures out north is actually south and what are the consequences? But I'm sure things are possible which I can't imagine.

The more info the station has the better. The 951 does not identify different tips, AFAIK, and some other cartridge systems have a way to transmit that information, so the station has at least that much more solid info to work off of.

 Assuming that dangerous projects controller worked at all with just a half millisecond's pause to get a measurement, the need for several cycle's worth of delay would appear not to exist. BTW, the use of a powerfet instead of the more common triac was explained by the OP as providing the finer control that a triac just cannot provide. He needed to be able to switch off a half millisecond ahead of the zero crossing event and back on half a millisecond after to create a measuring window that would have a negligible effect on power delivery to the heater. A triac simply couldn't be controlled by the micro-controller to this fine a degree.
 

Quote
Higher temperatures will require shorter refractory periods, coupled with longer on periods, making the controller's task to achieve temperature stability much harder. I suspect this may well be the reason for the KSGER's high temperature behaviour and the apparent 470 deg "ceiling" on maximum tip temperature that I've witnessed so far.
Yes, I agree that the higher the duty cycle, and the higher the heatsinking (the differential between 470C and ambient air > 350C and ambient air) the trickier it would be to get accurate temperature sensing. But FWIW, Hakko has set the limit of the 951 at 480C. I don't know how high the KSGER interface goes, but if it works reasonably well to 470C, that seems like it should be plenty hot. If you're at that temp to make solder joints, precise temp control probably doesn't matter, so long as the tip doesn't misregulate so bad it burns itself up. Anywhere near this temp, and you're smoking flux like mad, you're oxidizing any exposed iron plating like mad, and you're just gonna lift the iron when you see the joint flow. I mean, at this temp, you know you're not using the right tool for the job, already.

 Those KSGER and its copycats have the same 480 deg C limit. However, you can exceed this using the boost function. In my case, I've got the boost delta set to 50 deg for one minute which raises the target temperature to 530 deg which so far it has fallen far short of achieving, managing only to get to 477 deg as measured with my cheap Hakko FG-100 clone thermometer.

 I haven't bothered testing what happens if I set a 100 deg boost delta but I imagine it will obligingly show a target of 580 deg and not get the tip temperature much if any higher. In any case, the tip is oxidised enough as it is already from this extreme abuse and that of the calibration procedure which includes a 450 deg test point.

 Just to satisfy curiosity, I set the boost to a delta of 100 deg, set it for 480 deg, let it stabilise (which it now does quite quickly) and gave the knob the quick three or more clicks to the right to activate the boost and saw the expected 580 deg target temperature come up on the display.

 I didn't linger very long as I watched it failing to stabilise before giving the knob a quick leftward twist to cancel the boost, after which I set it back to 300 deg before giving it another quick leftward twist to enter the 150 deg standby mode and another such twist to put it into sleep mode from where the only way to wake it up is to push the knob to bring it back up to the set temperature.

 In sleep mode it displays the date and time, the "POFF" status and the tip and handle temps until the screen saver kicks in (it's an oled screen) by walking a display of the 'cold end' temperature in square brackets, with the word "sleeping" above, around the confines of the display to remind you that it is still powered up, effectively turning it into an expensive room thermometer.

 TBH, I really can't see any need to have a set temperature higher than 400 deg C anyway and that only to provide some margin for calibration error in high heat demand situations which, in the case of the KSGER unit with its boost function that can be set anywhere from 10 to 100 degrees, becomes a surplus requirement. I certainly wouldn't want to set it any higher than 350 deg C but I suppose it's handy to know you can perform life accelerated tests on your collection of fake or clone T12 tips on a whim. >:D

 I'm afraid to say that I still haven't tried the soldering station out 'in anger' for lack of room on my work table due to the collection of stuff, retrieved from my basement shack and workshop that had fallen into a state of neglect these past twenty years, to assemble my current GPSDO project which has ground to a halt whilst I upgrade my soldering facilities. I'm still waiting on a magnifying visor which I purchased as a backup to the Mustek microscope I'm also still waiting on taking delivery of from Banggood, along with some other soldering related goodies.

 I seem to be suffering a severe case of "AJRPS" (Arnold Judas Rimmer Procrastination Syndrome for Red Dwarf fans) in that I keep turning to my desktop computer to scour the internet for video reviews on soldering stations and smd workstation microscopes with LCD screens and 30v 10A bench supplies and other stuff I've bought from Bangood, not forgetting my activities here.

 However, today, I may have broken the deadlock by buying a couple of "Small Parts Organiser" drawers from our local Lidl store which I'd spotted just by chance whilst accompanying the XYL on a visit to our local library just across the road from the store, the walk to which was on account the XYL was after a bath seat and some odds and ends.

 As is normal when you don't park in the store's car park, you land up with a trolleyful of shopping that can't easily be carried in a couple of shopping bags (we could have managed ok except for my purchases), so I had to make the short walk back to the car to drive round to the store's car park to collect the XYL and the shopping.

 Anyhow, I digress. The important thing is that I now have the means to 'organise' my collection of parts into a less space consuming configuration that will allow me to clear enough space to not only allow me to resume my project but also to let me return my DSO to its rightful place alongside my cheap signal generator that's currently buried beneath the clutter, keeping its OCXO nicely warmed up.

 That purchase had been earlier yesterday afternoon and it's now 4 am and I still haven't removed the shrink wrap to check them out let alone actually put them to use. The bench clutter remains untouched which is why I think I've got a serious case of AJRPS. :( The problem is that when I returned with my prizes and parked them on the floor to eye up the mess on my bench, I realised it was going to be a bigger job to sort out than I'd envisioned when I bought those small parts drawers, thinking it would be "A quick Fix" so I did just what our fictional hero was famous for and sat down at my computer to 'mull the problem over'.

 I guess (hope, really) that it'll all look different after a good night's sleep when I have another look at the situation later this afternoon. There's some twenty years worth of computer related detritus gathered up on the rear half of this large desk to be sorted out as well which had rather dampened my enthusiasm to get stuck into the task when I'd returned with those parts drawers. With luck, I may have formed a stronger opinion of my KSGER soldering station by the end of this week.  :-DD :-DD :-DD

JBG

« Last Edit: September 21, 2019, 05:42:00 pm by Johnny B Good »
 

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #70 on: September 17, 2019, 05:20:15 am »
Quote
Assuming that dangerous projects controller worked at all with just a half millisecond's pause to get a measurement, the need for several cycle's worth of delay would appear not to exist.
Oh, I'm sure if he says so, he got readings. (I'm assuming he had to use back to back FETs in an SSR configuration).

The problem persists that the reading he gets will contain error, and it will not remain consistent just because he doesn't need to turn off the heater to get it. Depending on how long that heater has been on since it was last switched and depending on how much heat is being sinked out, it will change the error on the reading. It's cool he did that, but for many of us on the forum, this is child's play. Getting in, grabbing the tea leaves, and getting out... that's an afternoon of dicking around with a scope and microcontroller coding. I'd be much more interested to see the PID algorithm that can take this mess of tea leaves and come up with an accurate temperature reading. And to learn how you even start to tackle this kind of problem.




Looking at it from a God's eye view, it appears like a simple problem. Just turn it up when it sags. How hard is that? But looking at this as a programmer, the data you are working with is a sow's ear. You're in the middle of the Pacific with a broken compass. To get your true bearing, you have to go off course. And by the time you're back in the area you want to be, you are back to reading tea leaves.

Marketing: Awesome! Heats up in 10 seconds!

Management: Great!

Engineer: yeah, but OTOH...

Marketing: We eliminated overshoot!

Engineer: Well, technically the iron actually...

Marketing: We have a Boost Mode!* This is gonna be perfect on the brochure.

Management: Great job, guys. 

But, hey, I'm no math wiz. Maybe there's some elegant algorithm that does more than put a polish on this turd.

*Universal Truth: anything called Boost Mode is crap. And not everything can be fixed by software, even when the software guy is promising it. I'm being bugged by a client right now because a software guy has him convinced the impossible is possible. 1 second after reading his proposed solution, I responded with the reason why this won't work. I'm on my third email re-explaining it. I'm sure he will finally figure it out after convincing my client to fund the project, about 2 days before his delivery date, and then he will have new promises that will require just a tad more time and money.
« Last Edit: September 17, 2019, 09:24:56 am by KL27x »
 
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Offline Johnny B Good

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #71 on: September 18, 2019, 05:31:32 am »
Here's a youtube 'tutorial' by John Salt that attempts to describe how TS100 Soldering Iron Cartridge Tips Work.

 Unfortunately, in his mini-blowtorch heating test, he mistook the one millivolt per ohm reading of his DMM from the thermocouple/heating element for an actual change in resistance, jumping to the totally fallacious conclusion that the huge apparent drop in resistance was the means by which the controller sensed tip temperature.

 Perhaps if he'd been just a little more curious than he claimed to be and had kept applying the heat for just a few seconds more to see just how low an ohms reading he could get (it actually dropped to 0.4 ohms before it started increasing again), he may even have seen a negative resistance reading and finally correctly put two and two together and switch his DMM to the 200mV scale to unearth the fact that it uses a thermocouple in series with the heater element exactly like the system used by the Hakko T12 (T15) direct drive cartridge tips.

 Knowing as I do that heating element wire alloys are chosen not just for having a high enough melting point but also for having a very low temperature coefficient of resistance, it was blindingly obvious to me (as it should have been to John), that this wasn't a superstrong negative temperature coefficient of resistance sure to guarantee instant and destructive thermal runaway but some other phenomenon at work - the obvious contender being a thermovoltaic one, as in a thermocouple.

 It had struck me that the classic method of testing resistance with your typical DMM is that it simply to sets the voltage range to the lowest possible, typically 200mV and passes a constant current through the unknown resistance connected to its test leads which will translate directly to an ohms or K ohms or M ohms reading (1mA for the first two and 1μA for the 2 and 20MR with perhaps even 100pA for a 200M ohms range).

 I reckon his DMM must have been using a 1mA test current on its ohms range and, just fortuitously, was being applied counter to the emf polarity of the thermocouple in the tip. If he'd connected his DMM the other way round, he'd have seen an apparent increase in resistance with the applied heat and be even more readily fooled (I'd have still been suspicious and changed to the mV scale anyway).

 When I repeated this test for myself, I only had a simple gas lighter able only to produce a cooler yellow flame. Even so, I did manage to heat the K tip sufficiently to melt my 60/40 multicore solder which produced a mere 5mV from the thermocouple after I'd tried measuring the 'change in resistance' for each polarity of DMM connection which had shown me the expected decreased and increased readings with temperature rise.

 Anyway, aside from this shameful example of "scientific investigation", the thing I got out of this video was the fact that a much regarded soldering iron, the TS100, uses exactly the same "thermocouple in series with the heating element" principle as the T12 (T15) Hakko direct drive cartridge tips use.

 I hadn't previously taken too much notice of the TS100 oft mentioned in comparisons with the KSGER T12 soldering stations until now so was rather surprised to find that it's actually Chinese through and through. I was even more surprised to discover the relatively high prices commanded for replacement T100 tips (around the ten to thirteen quid mark, some three to four times the price of the Hakko T12 clones but around half the price of genuine Hakko T12 tips).

 The cold ends of the TS100 and the T12 tips look so identical, I'm surprised I couldn't find a TS100 compatible soldering handle for the KSGER T12 soldering station and its copycats (I did look! ;)). However, I did come across a couple of 3D printed adaptors to allow the cheaper clone T12 tips to be used in a TS100 handle. Presumably, the quality difference must be sufficiently small, possibly non-existent, for such adaptor projects to be worth doing just to shave 60 to 75 percent off the price of replacement tips.

 I think I'll stick with the existing pack of cloned T12 tips for now and see how they behave with extended use before I start spending any of my hard earned on a genuine Hakko tip. There doesn't seem to be any problem over temperature control if you keep below the 350 deg setting which is how I intend to use them anyway.

 It may not tick all the boxes in an industrial usage setting but this KSGER station should serve my hobbyist level requirements far better than my collection of basic Antex soldering irons, as fine as they are compared to others in this class of "plug into the mains and hope they get hot enough but not too hot" soldering irons in common use by many hobbyists thus far. I guess many of these basic soldering irons are soon destined for retirement after one last gasp use in fettling these cheap Chinese T12 soldering stations into serviceable and safe to use soldering station setups.  :)

JBG
 
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Online KL27x

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #72 on: September 18, 2019, 06:34:17 am »
I was sitting here watching the vid, and it brought back memories. Of burning up the first T12 tip I had in about the first 30 seconds with a bench PSU and alligator clips. And then....

Holy cow. When he showed the thing warming up on the O-scope I had to rewind. That thing responds great!!! Not the speed, but how the power looks (best I can tell; unfortunate, that there's jitter that throws off the analog scope) near full all the way to set temp and how it jacks to near full when cooled with the sponge. My T12 clones are junk! (I only wonder why he is testing at 200C, not something more applicable?)  Now I'm really curious how this thing works. It's bugging me. All you have is one crappy sensor, and a micro to log power delivery and sensor readings over time, and somehow that looks pretty damn tight. The power delivery looks aggressive, at least. I wonder about regulation and sag at soldering temp. Variation at set temp can probably be found in datasheet/marketing info. But sag?

Quote
Perhaps if he'd been just a little more curious than he claimed to be and had kept applying the heat for just a few seconds more to see just how low an ohms reading he could get (it actually dropped to 0.4 ohms before it started increasing again),
This brings back a memory. I made an iron controller years ago, using a PIC and an LCD. I had a cheap station at the time, and I just wanted this controller to drive this iron. I made the same mistake of measuring the resistance, thinking it had a thermistor. In fact, it was a thermocouple. But I had already plotted out the resistance over at least a score of different temps by the time I figured that out.  :-DD And... 

I got the thing sorted. Couple of opamps in series to amplify the thermocouple signal to the PIC. The firmware for the controls was done. And I said what the heck. I just used the resistance data I had recorded rather than re-doing voltage measurements. I just offset the ADC reading so that it was calibrated to a single measured temp of the lookup table, at 300C (or maybe the melting point of solder..). And it worked great. W/e the scale/curve, it was close enough across the board from min to max temp, 200-450Cish. I never tweaked a thing. But then I wasn't really too picky. It's just a number, and that's not the most important thing. I mean, it regulated fine, the range covered what I wanted, and making it more accurate to the numbers on the LCD wouldn't have made it perform any better.
« Last Edit: September 18, 2019, 07:03:15 am by KL27x »
 
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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #73 on: September 18, 2019, 09:53:55 am »
In that video he says "keeping the tip absolutely at the right set temperature". Yet the display is magically sitting on 200C the whole time and no tip measurement was actually taken to prove this.

I'll break it down for you. There is a large variance between the tip temp and display temp and the lag between them. So while it's displaying 200C/390F the tip could actually be still at 100C/210F. When it reaches actual stable temp regulation (as opposed to what the display says) the tip can still be as much as 30C/85F low. Obviously there is different firmware to correct the issues but it makes performance worse not better. The other thing is, if anything this is lower mass than a standard T12 tip.
Soldering/Rework: Pace ADS200, Pace MBT350
Multimeters: Fluke 87V, 117, 27/FM     >>> Fluke 51/52 Thermometer Parts Required <<<
Oscilloscopes: Rigol DS1054Z, Phillips PM3065
 
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Offline Johnny B Good

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Re: Hakko still the best option for a good quality hobbyist soldering station?
« Reply #74 on: September 18, 2019, 04:55:25 pm »
In that video he says "keeping the tip absolutely at the right set temperature". Yet the display is magically sitting on 200C the whole time and no tip measurement was actually taken to prove this.

I'll break it down for you. There is a large variance between the tip temp and display temp and the lag between them. So while it's displaying 200C/390F the tip could actually be still at 100C/210F. When it reaches actual stable temp regulation (as opposed to what the display says) the tip can still be as much as 30C/85F low. Obviously there is different firmware to correct the issues but it makes performance worse not better. The other thing is, if anything this is lower mass than a standard T12 tip.

 With this sensing technique, it seems to me that there'll be very little difficulty in accurately sensing the thermocouple voltage (it's a very low impedance source, in this case dominated by the eight ohm series resistance of the heating element). Although the circuit is only shielded by the ESD earthed tip, leaving about a metre of unshielded silicone insulated cable betwixt thermocouple and opamp input, the eight ohms impedance kills off any electric field interference effects leaving only magnetic induction to worry about.

 In the case of far off sources of magnetic field interference, say a mains transformer more than a couple of inches away, the close coupled return conductor will effectively cancel out any such induced voltages anyway, leaving only induction from adjacent wires in the cable to worry about. Since the one and only major source of such interference, the heater current, is shut off during these brief measurement periods, even this isn't an issue.

 The main issue in this case being the heat pollution from the heater section of our thermocouple circuit and the modicum of self heating of the nichrome wire leading into the thermocouple junction itself. If they've used a relatively large thermal mass crimp to create the hot end junction of this thermocouple, that could allow its temperature to be dominated by the heat from the tip itself, swamping out any heat leakage along the heater wire and that caused by self heating.

 It's not the perfect way to sense tip temperature from a thermocouple but as long as it's within 20 degrees of the tip rather than 20 degrees of the heater section, a lovingly crafted PID algorithm should be able calculate (more accurately 'guess') the actual tip temperature sufficiently well enough to be within acceptance for practical use in controlling tip temperature.

 Considering that the older alternative use of an electrically isolated thermocouple sensor circuit doesn't escape the effects of heat pollution from the heater either, the accuracy of this new system could well be better, given a clever enough PID algorithm and an improved design of direct drive cartridge tip.

 Given that, for reasons of practical limitations, the tip temperature can only be assessed from sensing on the hot side of the tip rather than the contact point with the workpiece, having a modest amount of overshoot is far more preferable to having a perfect ramp up to temperature with no overshoot and even more preferable again than a response that has any undershoot whatsoever.

JBG
 


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