[Solved by throwing breadboard in the trash] OPA336 : no output with arduino

Hi everyone,

I'm trying to build a soldering station using the Weller RT Tips. I'm using the schematics from those projects.

I have a 12V supply going to an LD1117V50 to give me a +5V output. GND on the 12V and 5V side are shared.

My oscilloscope is showing me the output of the OPA336.

The OPA336 works fine when it's alone in the circuit with the LDO, I can get an amplification of the heat sensor inside the Weller RT tip, but as soon as I plug my Arduino, the output goes to 0. I don't even wire the OPA to an analog input, just powering up the Arduino from the +5V and GND of the LDO.

I tried various pins for powering on various arduino boards and models (Arduino Pro Micros with an ATMega32u4 and Arduino Pro Minis with ATMega328P). I even tried an Amica NodeMCU and a bare ATMega168 chip, same thing...

The OPA336 left alone consumes 0.02mA, plugging the Arduino Pro Mini brings the current consumption to 11mA, so it doesn't look like the LDO is being overloaded and can't supply enough current.

Anyone has any idea ? I'm at a loss right now.

Please read and follow the instructions in the "How to use this forum" post.

Something is probably wrong with your circuit, which you forgot to post.

Thanks for the answer.

Here is the part I am testing. I left out the power supply since it’s working fine.


as soon as I plug my Arduino, the output goes to 0.

Please explain what you mean by "plug in the Arduino", and add the missing details showning how ALL the parts are powered.

It seems likely that you have a power/ground problem.

Well, as it happened more than once, seems to be a breadboard problem : I soldered the LDO + capacitors and the opamp (changed for an LM324 for now) with the accompanying resistors and capacitors to a perfboard, and it seems to work now... Sorry for bothering you with this useless post.

@jremington : The problem I had was that the opamp was working fine (showing 100s of mV on the output), but as soon as I wired the VCC & GND of the arduino to the power rails on the breadboard, the output of the opamp dropped to 0v. Removing the jumper wire from either VCC or GND brought the output back to the right value.

"Solved by throwing breadboard in the trash"

Was it a looong breadboard with split power rails in the middle...

Nope, a basic 600 points with power rails on the side, with blue and red lines to indicate VCC & GND. I might have bought that one on aliexpress a long time ago...