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Atten SMD tweezers: need soldering station schematic (ST-1509 or GT-6200) HELP

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riccardo.pittini:
Hi

I am working on a new version of a hobby soldering station. The first version I made (SolderingRT1, https://gitlab.com/pittinihub/solderingrt1) works very well with Weller RT tips and tweezers.
However, I wanted to add functionality and make it compatible with other tips (like JBC and others).
The Weller tweezers are expensive and recently Atten made some similar ones (example: ST-1509 N9100). These are very similar to Weller ones.

Example:
https://www.aliexpress.us/item/3256803404139133.html?gatewayAdapt=glo2usa4itemAdapt


The Atten tweezers ST-1509- N9100 have a very similar structure as Weller. They work with 12V (3R resistive element) and have a thermocouple.
The connections are the following: HeaterLeft, TCleft, GND, TCright, HeaterRight. The thermocouple type is different than the Weller but, I can fix that with a proper calibration and mapping.

Now the main challenge:
- In the Weller tweezers the TC are reference to GND and they generate a positive voltage compared to GND like few mV that then get amplified etc..
- In the Atten tweezers the TC seem reference to GND but "inverted polarity" so actually they generate a negative voltage on the TCpin

As the voltage on the Atten tweezers is negative I cannot the normal amp stage I used before. A solution would be using a differential amplifier with dual supply and adding an offset to it. However, this adds expensive opamps (I am trying to make it KISS style) and a bit of complexity.
So I wanted to try to get inspiration from Atten designers :).

Does anyone has an Atten station (ST-1509 or GT-6200) and can post some pictures of the PCBs /teardown?
Or does someone has a schematics for those stations?

Thanks everyone

2N3055:
Are you sure about polarity of TC?

Mine certainly does not generate negative signal in reference to ground.. It will generate approx. 10 mV at 400 °C.
You need noninverting amp 250-300x to bring it into 3.3V range.  You will need to experiment to calibrate it correctly.

Don't measure while current is flowing into heater because heater and TC have common return wire.

2hry:
Hi
I dont have an atten station, but i have ordered only the tweezers.
Like you, I also thought I´d make my own controller, and noticed the negative voltage referenced to ground.

I´m going to try it like that, when my pcbs arrive(approx. 2weeks) made Dual Resistors -- marked green:Atten -- other side: Weller

2N3055:

--- Quote from: 2hry on October 03, 2023, 06:42:07 pm ---Hi
I dont have an atten station, but i have ordered only the tweezers.
Like you, I also thought I´d make my own controller, and noticed the negative voltage referenced to ground.

I´m going to try it like that, when my pcbs arrive(approx. 2weeks) made Dual Resistors -- marked green:Atten -- other side: Weller

--- End quote ---

Heat up the tip. It is not negative  when hot. It might be some µV at room temp. But as soon as you heat it up it gets into positive mV range.

That is for GT-N100.

riccardo.pittini:
It is negative like 8mV at 340C. I probably measure it 10 times, checked re-cheked multimeter cables etc... That's just how it is and very annoying...
 
Calibration is not a problem (the one I have doe with the Weller resulted in a temp in +-1C :) )

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