It looks like aixun just released a new station
As promised, I played around with my scope again:
Any ideas?
I just came across this amazing project called the AxxSolder https://github.com/AxxAxx/AxxSolder. I wish I had found this sooner, I would have never bought the Aixun. Bom cost is about 60 bucks, could power T245 and T210 from any DC source 9V-24V. Looks really well engineered. Pair this with any switching supply, or even 18650 batteries, and genuine jbc handle and tip, looks like a total winner.
As promised, I played around with my scope again:
Any ideas?
well perhaps you already know what i had left to say (to repeat myself):
replace the (5) electrolytic caps. then retest again after that... just do the simplest and most obvious thing 1st.
- I was able to reproduce that AC measurement on the SMPS output, but what exactly are we measuring there? @drsky
Measuring the heater signal with probe at Q4-B, Q4-GND again led to weird measurements.
replace the (5) electrolytic caps. then retest again after that... just do the simplest and most obvious thing 1st.
It completely avoids the common GND problem, while one could easily add earth (probably 1M resistor *required* and I'm not sure if a SMPS with grounded negative would work then... hmm)
It completely avoids the common GND problem, while one could easily add earth (probably 1M resistor *required* and I'm not sure if a SMPS with grounded negative would work then... hmm)
How does JBC do it? Do they put 1 meg resistor between tip to earth? Or do they just connect the supply negative to earth?
You can see how JBC did it here where johnmx did reverse engineered the JBC CD-2BC: (he attached a PDF of the schematic in his first post) https://www.eevblog.com/forum/testgear/jbc-soldering-station-cd-2bc-complete-schematic-analysis/
They use 0.44 ohm resistance with a fuse between PE and the tip of the cartridge. If the fuse burns there is still a 1M ohm resistance. I
Nice to see you here, AxxAxx . Welcome!
The main difference here is, that JBC uses a toroidal transformer, not a SMPS.
Yes, indeed it gets more complex the more I think about it. Also considering that the grounding should work equally well with floating SMPS's and grounded negative ones and at the same time not influence the temperature reading.
I guess we should lift this discussion out in a separate forum thread
and not hi-jack "Any opinions on the AiXun T3A" if people are interested in the AxxSolder project.
Well, Hi!
I saw this question about protective earth comming up here and on the youtube DEMO.
They use 0.44 ohm resistance with a fuse between PE and the tip of the cartridge. If the fuse burns there is still a 1M ohm resistance.
(How) would different options influence temperature measurement? Because connecting both tip and SMPS GND to earth means pulling -IN_A of the opamp to GND as well... does that hurt, or is it no problem because -IN_A has no reference to GND anyway?
Oh well, what about creating a pcb that fits into the T3A case?
I guess we should lift this discussion out in a separate forum thread and not hi-jack "Any opinions on the AiXun T3A" if people are interesed in the AxxSolder project.
(How) would different options influence temperature measurement? Because connecting both tip and SMPS GND to earth means pulling -IN_A of the opamp to GND as well... does that hurt, or is it no problem because -IN_A has no reference to GND anyway?
Marco Reps made a video about this when he did his open source JBC station (https://youtu.be/cYgjcDbSyRE?feature=shared&t=256). Quoting him:
- "The tip is permanently grounded because best practice, the whole controller section must also be referenced to mains earth which is you know very common BUT if also the heater supply voltage was referenced to mains earth, there would inevitably be unwanted currents through the thermocouple. The easiest solution is to use the transformer with two independent output voltages: one is rectified, referenced to mains earth, and regulated it down to the needs of the controller. The other one is exclusively for the heater and its circuit can be controlled with our optically isolated solid-state relay."
He explains it really well in that video. The heater supply and controller supply should be isolated and only interact with optocouplers.
Oh well, what about creating a pcb that fits into the T3A case?
I don't know about getting it to fit in a T3A case though. If the handle, controller, and power supply in the Buzzxun all suck, I am struggling to see the big value proposition in this fully-glued $100 product. I don't even like the case because the top doesn't open, and it's just a tube which makes it hard to work in. Probably the only good thing here is the cradle (and even that is made of plastic), but this can be bought separately.
[...] but get rid of the mercury switch?
Mercury in the handle. Mindblowing.
Thank you!
Another point to make, despite the "200W" claims for the power supply, it is only ever loaded up for many seconds and does not need to be designed for full power 24/7. So we have a "200W" SMPS further cheapened because the duty cycle is ~20% at worst. I see nothing wrong with it sagging a volt or two under load.
But... it's been cheapened twice maybe three times... the heatsinking, electrolytic capacitors etc. are surely under the minimum for reasonable life.
Ah, well, the problem is not mains earth but the fact that when PE + GND are connected, you get a current from the heaters positive through the TC to the grounded tip
we have a "200W" SMPS further cheapened because the duty cycle is ~20% at worst. I see nothing wrong with it sagging a volt or two under load.
But... it's been cheapened twice maybe three times... the heatsinking, electrolytic capacitors etc. are surely under the minimum for reasonable life.
Ah, well, the problem is not mains earth but the fact that when PE + GND are connected, you get a current from the heaters positive through the TC to the grounded tip
Precisely. When using a dc supply, the best setup seems to be
-connect the tip to earth
-the thermocouple will then be referenced to earth, so connect the control board supply negative also to earth
-use a floating and isolated smps for the heater and turn on and off its mosfet with an optocoupler
One can use an off-the-shelf isolated dc-dc converter to get the 24V down to 5V, for example something like PQQ6W-Q24-S5-S (https://www.mouser.com/ProductDetail/CUI-Inc/PQQ6W-Q24-S5-S?qs=zW32dvEIR3sbKuWv4BvdLw%3D%3D) to run the controller board.
I guess we should lift this discussion out in a separate forum thread and not hi-jack "Any opinions on the AiXun T3A" if people are interesed in the AxxSolder project.
Make one please.
If you were to put a genuine JBC tip in the Aixun handle, 8A of current will be flowing in the thermocouple. Yikes!
Which one is it? One of these is wrong and misleading. Even if the thermocouple doesn't get damaged by it, I would still rather only use the thermocouple for what it was designed to be, not a second heater.
I don't like how there is conflicting information about what the pinout of the C245 cartridge is.
...
Which one is it? One of these is wrong and misleading.
Even if the thermocouple doesn't get damaged by it, I would still rather only use the thermocouple for what it was designed to be, not a second heater.
@AxxAxx don't waste your time on C245, see above, but cutting C210 like this would be nice!
Someone already did the measurements. http://adgd.ru/2021/01/04/jbc-soldering-cartridges-pinouts/