Author Topic: T12 STM32 V2.1S Soldering Station Controller - schematic etc.  (Read 2310 times)

0 Members and 1 Guest are viewing this topic.

Online Gandalf_Sr

  • Frequent Contributor
  • **
  • Posts: 954
  • Country: us
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #25 on: November 07, 2019, 07:30:57 pm »
Johnny B Good

Thanks for the brief summary in defense of the KSGER design.  I would appreciate if you could outline your suggestions for 'upgrades' perhaps as bullet points.  :D
I'd like to make the world a better place but they won't give me the source code
 
The following users thanked this post: mematyi

Offline mematyi

  • Contributor
  • Posts: 8
  • Country: hu
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #26 on: November 07, 2019, 09:39:01 pm »
Great point!

As many people are purchasing the iron these days, it would be great to have a summary/guide of all the modifications at one place.

With the help of this thread, I removed the heatsink from the PSU, clipped the side of it, and removed the soldered legs. Now it has at least 3mm of clearance from the HV side. I also connected the chassis to the PE, and verified that the PE goes to the tip. It does, because the PSU's 0V output is tied to the PE, and the 0V is connected to the iron handle minus and Earth as well on the pcb.

According to the schematic published here, the iron actually has a separate GND and Earthing up to the controller. I think it would be great to separate those, and connect the chassis and controller board to the PE, but add a small resistor between the Iron Earth and PE, to limit the possible current. Does it make any sense?
« Last Edit: November 07, 2019, 09:40:44 pm by mematyi »
 

Offline Johnny B Good

  • Frequent Contributor
  • **
  • Posts: 254
  • Country: gb
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #27 on: November 08, 2019, 05:22:00 am »
Great point!

As many people are purchasing the iron these days, it would be great to have a summary/guide of all the modifications at one place.

With the help of this thread, I removed the heatsink from the PSU, clipped the side of it, and removed the soldered legs. Now it has at least 3mm of clearance from the HV side. I also connected the chassis to the PE, and verified that the PE goes to the tip. It does, because the PSU's 0V output is tied to the PE, and the 0V is connected to the iron handle minus and Earth as well on the pcb.

According to the schematic published here, the iron actually has a separate GND and Earthing up to the controller. I think it would be great to separate those, and connect the chassis and controller board to the PE, but add a small resistor between the Iron Earth and PE, to limit the possible current. Does it make any sense?

 Before purchasing mine last August from Banggood (who had uncharacteristically shipped it out to me from their Chinese warehouse - cheapest option- in just 8 days!), I'd looked at countless youtube review videos so was well prepared to tackle the remedial work on the PSU and that 10K R10 battery draining resistor (as well as the need to fettle the wiring of the supplied 9501 handle which had guided my choice of soldering station - the alternative handle options had all looked rather naff to my mind).

 It turned out that this resistor had not been placed on the control board in mine, neatly explaining the 3.16v reading I saw when checking the plug in CR2032 cell which had been stuck to the side of the diode heatsink rather than jammed between the top of the psu transformer and the case lid - I relocated mine to the base of the case just under the LV end of the psu board, clear of any PTH wires.

 Since I had a 180W Parkside soldering gun stored unused since I'd purchased it from Lidl a year earlier, I decided to put it to use to sweat the heatsink off the board and reshape all three fins that overhung the "Isolation Slot" using a junior hacksaw and file to provide a healthy airgap to that 340vdc trace coming from the BFO smoothing cap rather than just ease it up enough to slide a layer of insulation tape in between said trace and the heatsink fin. I didn't have any kapton tape otherwise I may have used that method instead. Either way works - I just happened to have a BFO soldering gun to hand is all. :)

 Compared to that rather scary reliance on just a thin layer of solder resist mask to insulate the heatsink from a source of 340vdc, the 2mm creepage clearance between the retaining lug and mains voltage seemed positively generous so I left it alone. It's not ideal but the risk is low enough once the case is earthed.

 However, I must admit that it hadn't occurred to me to check whether the aluminium case had any earth connection until seeing another video review shortly after getting it "all sorted" as I'd thought in a moment of hubris, so I landed up stripping it apart yet again to rectify that particular Chinese sin of omission. Then, a little later on again, I discovered that the oval TPH which the unsoldered rotary encoder retaining tabs passed through weren't actually connected to the groundplane so had to solder short straps to nearby grounded points on the board for good measure.

 Which now reminds me that it might be a good idea to run an additional earthing wire from the soldered up retaining tabs as a belt to my braces soldering of an earthing strap from the PE tag directly onto the GX12-5 socket's barrel (I hadn't wanted to drill a hole into the case just to fit an earthing tag).

 I'm not sure (I've lost track of all the various sources of such useful information on these mods) but this last one may have been a floobydust inspired mod since I think I did the ground bootstrap diode mod across the heater element suggested by him to suppress voltage spikes at the same time.

 I used one of three BY298 diodes that I'd had in my parts bin for the past four decades just waiting to be put to good use - this seemed a golden opportunity to finally get some return on whatever my initial investment had been. Whether it makes any difference is hard to tell but I'm sure anything that suppresses voltage spikes on the input circuitry of an opamp dealing with mV level thermocouple signals is no bad thing.

 The one constant in all of this was the fact that the soldering iron tip was always fully grounded via the PE connection in the C14 mains socket (the only thing in fact that was actually earthed!). I know the idea of using a 1MR static drain resistance connection to the tip is largely deprecated by most, including myself but I can see where this could be useful in those rare usage cases such as working on ancient live telecoms kit running off 52 volt DC power to have an insulated tip with not even a static drain connection to ground for ESD protection. TBH, I can't see any such need these days with modern modular telecoms or IT kit nor with any other kit you might find yourself working with.

 Unless you have an essential need to work on live low voltage kit, you'd be better off with a low resistance earth connection to the soldering iron tip and work on circuit boards only when they are disconnected from their power source. You could try fitting a 1MR static drain with a bypass switch to let you choose whatever option seems best but this does leave room for mistakes. If you are going to use a resistive connection to earth the tip, just ensure that everything else (0v rail and the case metalwork) remains connected to the safety earth (PE tag in the C14 socket).

 I guess if such an option is desired you could use a two pole switch so you can light up a warning lamp to indicate when it's safe to use on live low voltage kit and when it's not safe. Even with such an indication scheme, the risk of getting the setting wrong still remains.

 In this case, using a low voltage DC (or AC) supply to power the heating element allows you to use a lowish value resistance, such as 10KR to 100KR, in place of the more usual 1MR static drain to earth with an acceptably low risk of damage to any unpowered delicate electronic components you may be working with. You could embellish such an arrangement with a leakage voltage detector circuit to trigger a warning of the presence of any undesirable voltage on the tip that could arise out of a breakdown of the insulation between the heating element and the tip itself - your call.

 The full earth contact to provide an ESD safe soldering iron is really an inheritance from soldering irons using mains voltage heating elements where the issue was not only one of ESD risk but also one of safety against the risk of electrocution.

 In the case of this KSGER T12 soldering station, you have some freedom to DIY whatever ESD protection scheme you fancy but it's best to avoid unnecessary complexity. The general advice here is "Make it no more complex than it absolutely needs to be (and, ideally, less complex than that)", which usually boils down to in this case, leave it as it is (the tip stays directly connected to the PE tag on the C14 socket).

 One alternative that could neatly address the occasional need to work on live kit is to add a socket so you can run the station off a 5s or 6s LiPo pack with the mains disconnected. Depending on your choice of battery pack, you could get several hours of use per charge, especially if you take full advantage of the low temperature standby and power down modes.

 Unless I'm very much mistaken, the smpsu should tolerate the application of battery voltage on its output when powered off (disconnected completely from the mains), leaving only the need to use a suitable diode in series with the battery supply to eliminate the risk of accidental backfeed should you power it up from the mains without unplugging the battery pack.

 If you use a 5s LiPo pack you could include a basic battery charging controller to let you use the smpsu to recharge the battery pack. You could do the same with a 6s pack but the charge controller will need to provide a small voltage boost which may make it a little more expensive an option. In this case, I'm assuming the use of a LiPo cell balancing and overcharge protection circuit in or attached to the battery pack.

 I've seen several examples of such battery powered stations built from KSGER kits but I can't recall seeing any based on the addition of a battery pack to an existing mains powered station. It might be worth taking a look, even if it's just to get some ideas on how to provide a battery power option to the existing mains only powered T12 soldering station if such an alternative has any appeal (freedom to work away from the mains supply with no troublesome earth contact to interfere with low voltage live circuits).

JBG
 
The following users thanked this post: mematyi

Online Gandalf_Sr

  • Frequent Contributor
  • **
  • Posts: 954
  • Country: us
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #28 on: November 08, 2019, 03:00:41 pm »
JBG.

That all makes sense but a picture showing all these improvements would also be a great help. Any chance?
I'd like to make the world a better place but they won't give me the source code
 

Offline Johnny B Good

  • Frequent Contributor
  • **
  • Posts: 254
  • Country: gb
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #29 on: November 08, 2019, 05:28:39 pm »
JBG.

That all makes sense but a picture showing all these improvements would also be a great help. Any chance?

 I do regret not making a photographic record of the various modifications (before and after shots) so when I next take it apart to add that extra earth strap I mentioned, I'll rectify that omission and attach a few key photos to highlight not only the extra earth strap addition but also the modifications I'd applied since purchasing it.

 I'll try to fulfil this request for "photographic evidence" with a little more alacrity than your previous respondent had managed. Normally, my expertise in the fine art of procrastination doesn't bode well for such an outcome I'm sorry to say and you could probably place a large value order with Banggood and have it actually delivered before seeing any photos. However, since it's such a trivial modification and safety related, I might surprise us both in the next day or so. :)

 No promises but I'll do my best.

JBG
 

Online Gandalf_Sr

  • Frequent Contributor
  • **
  • Posts: 954
  • Country: us
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #30 on: November 08, 2019, 07:59:39 pm »
JBG, NBD, FYI, JPGs
I'd like to make the world a better place but they won't give me the source code
 
The following users thanked this post: Johnny B Good

Online Gandalf_Sr

  • Frequent Contributor
  • **
  • Posts: 954
  • Country: us
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #31 on: November 08, 2019, 08:13:54 pm »
So to aid in the cryptic post above, the problem is that the 300+ Vdc track highlighted is really close to the heatsink for the diode on the low voltage side.  Here's the steps to ameliorate:
1. Make sure the 400 volt capacitor is discharged
2. Carefully remove the heatsink (I used a Hakko FR301 desoldering gun - awesome piece of kit)
3. Remove the corners of the 2 heatsink splines as shown - this can be done with a good pair of cutters as the aluminum (similar to aluminium) is really soft
4. Place a small amount of Kapton tape as shown (electrical tape, aka insulating tape in Blighty, will do)
5. Refit the heatsink using a small amount of heatsink compound on the diode
6. Use soldering station with less risk of self-electrocution

As you can see, I'm bi-lingual
« Last Edit: November 08, 2019, 08:28:59 pm by Gandalf_Sr »
I'd like to make the world a better place but they won't give me the source code
 
The following users thanked this post: Johnny B Good

Offline Johnny B Good

  • Frequent Contributor
  • **
  • Posts: 254
  • Country: gb
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #32 on: November 08, 2019, 11:59:04 pm »
 Nice photos! :)

 I took mine apart earlier this evening to take a few pictures (I'll sort out the extra earth strap tomorrow) and took exactly the same shot as your third image. It's a tricky shot to get right, especially if you're using macro to get close in as I think both of us did.

 I don't think I took any "before and after" shots of any of my previous modifications but I'll have a search just in case I did as a "Just might be worth documenting this work" thing and just put them out of mind, having done what I'd needed to do without any further thought of doing a "Show and Tell" session. If I find any previous pictures, I'll include a choice selection with my latest batch once I've recorded this, hopefully, final earthing modification work.

JBG
 

Offline BlackICE

  • Contributor
  • Posts: 8
  • Country: us
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #33 on: November 09, 2019, 05:36:03 am »
I took my heatsink off with a FR 301 too. Without it would have been a PITA since my other solder station is a Weller 1010NA. That and solder wick probably would work too well. I did add a fuse for the primary on the Weller.

I didn't connect the negative of the secondary's output to PE. Is that necessary? I presume of the heating coil malfunctions  the grounded tip cause a fuse to blow. Likewise as long as you ground the case if the heatsink shorts to the HV trace it will likely not causes an immediate problem (if the case is closed) as the diode has a non-conductive plastic case. Of course I'm only using 120v AC not 240 like some do with much more risk.

IMO the mods in priority order are.

1. GND the case to PE.
2. Better isolate the heatsink from the HV trace.
3. GND the negative of the sencondary to PE.

Any think else? Some people did something to better protect the output MOSFET.


« Last Edit: November 09, 2019, 05:38:56 am by BlackICE »
 

Online Gandalf_Sr

  • Frequent Contributor
  • **
  • Posts: 954
  • Country: us
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #34 on: November 09, 2019, 10:28:16 am »
Nice photos! :)

 I took mine apart earlier this evening to take a few pictures (I'll sort out the extra earth strap tomorrow) and took exactly the same shot as your third image. It's a tricky shot to get right, especially if you're using macro to get close in as I think both of us did.

 I don't think I took any "before and after" shots of any of my previous modifications but I'll have a search just in case I did as a "Just might be worth documenting this work" thing and just put them out of mind, having done what I'd needed to do without any further thought of doing a "Show and Tell" session. If I find any previous pictures, I'll include a choice selection with my latest batch once I've recorded this, hopefully, final earthing modification work.

JBG
Thanks. Believe it or not, they were taken on my iPhone 7+ on 'x2' which uses the second camera - the phone was very close to the subject and I touched the screen right at the point I was interested in to set focus and exposure at that point. The resolution has been reduced to make the file size smaller.
I'd like to make the world a better place but they won't give me the source code
 

Offline mematyi

  • Contributor
  • Posts: 8
  • Country: hu
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #35 on: November 09, 2019, 11:03:15 am »
Hi!

Can you describe this Bootstrap diode mod?
You placed a diode across the heater, but in which orientation?
I think it might actually beneficial to do, as many of my T12 tips have fluctuating temperature reading on higher temps. They have been broken in and calibrated, only this is the (mainly aesthetical) problem.
 

Offline Johnny B Good

  • Frequent Contributor
  • **
  • Posts: 254
  • Country: gb
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #36 on: November 09, 2019, 03:40:25 pm »
Hi!

Can you describe this Bootstrap diode mod?
You placed a diode across the heater, but in which orientation?
I think it might actually beneficial to do, as many of my T12 tips have fluctuating temperature reading on higher temps. They have been broken in and calibrated, only this is the (mainly aesthetical) problem.

 If you look at floobydust's starter post to this thread (https://www.eevblog.com/forum/reviews/t12-stm32-v2-1s-soldering-station-controller-schematic-etc/msg2463234/#msg2463234), he mentions adding a ground clamping diode (not bootstrap diode - my bad in sloppy choice of wording :-[) which is shown in the bottom left quadrant of the circuit diagram he posted this link to:

 https://www.eevblog.com/forum/reviews/t12-stm32-v2-1s-soldering-station-controller-schematic-etc/?action=dlattach;attach=755412

 Once I've added the extra ground strap later today, I'll post a photo showing how I'd added a BY298 diode substitute for his suggested RS1M smd diode to my controller board.

 I can't really say with any certainty whether this modification improves the behaviour of the controller. All I can say is that it won't (and appears not to) do any harm. Its presence reduces stress on the input protection filtering circuit of the TC opamp which could otherwise create a reliability issue in the longer term. It may be nothing more than a 'snake oil' placebo effect but if so, at least it's cheap "snake oil". :)

 As for this business of having to "burn in" these clone/fake T12 tips before they lose their initial instability, my best guess is that it's the result of galvanic action from residual moisture which gets driven out of the heater/thermocouple cartridge assembly after several minutes of first time use.

 This behaviour with virgin clone/fake T12 tips seems to be a universal experience amongst users of these cheap tips. So far, I've not seen anyone stepping forward to announce whether genuine brand new Hakko T15 (or T12) tips show exactly the same initial behaviour or not.

 It may simply be that Hakko have merely thought to run a final drying out stage in their production process which the Chinese clone manufacturers deem unnecessary, leaving their customers to deal with it as a commissioning "Burn In" operation.

 If I'm right in this hypothesis of residual damp and transient galvanic effects (there could be a completely different mechanism at work here but damp and galvanic seems the most likely cause), that implies some initial electrolytic corrosion effect taking place during this brief running in / drying out process from the use of DC current by these KSGER units.

 How deleterious this may be to the long term life of the cartridge heater/thermocouple assembly is unknown but initialising these tips using a 12.6v ac valve(vacuum tube) heater transformer supply to minimise such potential electrolytic corrosion could provide a useful extension to the service life of these clone/fake tips (assuming all the other shortfalls in quality don't kill these tips first).

 Even if such a low voltage ac drying out/burning in setup makes little difference to the long term life of these tips, if you're in the habit of buying your clone tips in packs of ten, it might be worth trying, if only to let you commission your clone tips in bulk without tying up your soldering station with this task, especially if you already have a suitable low voltage (8 to 12vac 20VA) transformer to hand (with perhaps suitable dropper resistors to extend your transformer voltage options a little further).

 You could even repurpose an ancient car battery charger to this task, perhaps one with a burnt out rectifier which will be redundent in this case, giving it a new lease of life. For anyone intrigued enough by the thought of safely commissioning their new clone tips without tying up their soldering station with such an otherwise unproductive use, such a setup needn't cost them a penny in materials and only an hour or so's worth of their (usually ample) spare time to run such an experiment.

 I'd run this experiment but ICBA to simply for lack of time (and, quite honestly, motivation) but don't let my own lack of 'get up and go' put you off the idea. If I could get a round tuit, I'd do it myself. The problem is that up to now, I haven't quite reached the 'bulk soldering up' stage with any of my own projects to justify the modest time investment required.

 It's just an idea for a little side project that I've put on the back burner to simmer whilst I try and sort out my real project, a basic DIY GPSDO which I've been working off and on during the past six months or so (along with some unfinished work on an already much modified Feeltech FY6600 signal generator).

 Anyone's welcome to run with this "neat idea" of mine if they're looking for a potentially useful experiment to play around with. It may prove a complete waste of time but even a "failed experiment" (strictly speaking, there's no such thing as a "failed experiment" unless it stops a money earning project dead in its tracks) will tell you something new.

JBG
« Last Edit: November 09, 2019, 08:38:12 pm by Johnny B Good »
 
The following users thanked this post: mematyi

Offline floobydust

  • Super Contributor
  • ***
  • Posts: 2953
  • Country: ca
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #37 on: November 09, 2019, 05:53:13 pm »
The extra clamp diode goes across the heating element at pin 4,5 on the GX12-5.
This protects the mosfet and tip temp circuit from -ve voltage spikes due to back-EMF or ESD. Any fast recovery or 40V Schottky diode 1N5819 would work.
For +ve voltage spikes, the mosfet's internal diode covers that.
C8 provides a little coverage but it's absent on many controller boards.
 
The following users thanked this post: mematyi

Offline Johnny B Good

  • Frequent Contributor
  • **
  • Posts: 254
  • Country: gb
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #38 on: November 09, 2019, 08:50:11 pm »
 As promised, a whole bunch of photo attachments from today's earthing modification. I think it'll take more than one posting to deliver the 20 image files I selected. ::)

JBG
 
The following users thanked this post: bitwelder, mematyi

Offline Johnny B Good

  • Frequent Contributor
  • **
  • Posts: 254
  • Country: gb
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #39 on: November 09, 2019, 08:53:42 pm »
Here's the next bunch of pictures:
 
The following users thanked this post: bitwelder, mematyi

Offline Johnny B Good

  • Frequent Contributor
  • **
  • Posts: 254
  • Country: gb
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #40 on: November 09, 2019, 08:56:32 pm »
Here's the next five photos

 
The following users thanked this post: bitwelder, mematyi

Offline Johnny B Good

  • Frequent Contributor
  • **
  • Posts: 254
  • Country: gb
Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.
« Reply #41 on: November 09, 2019, 09:00:05 pm »
 And, finally! The last three photos.

 I renamed them with a descriptive title which should explain what each one is. You can always ask for clarification if desired.

JBG
 
The following users thanked this post: bitwelder, mematyi


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf