Trouble with multiple voltage dividers

Discussion in 'The Projects Forum' started by Andrei Fejes, Jun 9, 2016.

  1. Andrei Fejes

    Thread Starter New Member

    Jun 9, 2016
    I’m using an ESP8266-DEV to measure battery voltage and control some LED lights.

    The first 2 voltage dividers are used to get the voltage bellow 1V, required by the ADC GPIO – it is working fine.

    The third voltage divider lower the voltage bellow 0.4V, in order to power down the Pololu S10V2F12 12V step-up, by keeping the SHDN pin powered during sleep cycles of the ESP.
    By setting GPIO12 on HIGH, the 12V module activates, and through IRL510 MOSFET I can control the LED light.

    In my prototype the circuit works fine, but on my PCB design the third divider either not give me any voltage, or give me the same voltage as input, and the MOSFET is behaving glitchy – every couple of seconds it turn off and on. I’ve even managed to burn one ESP...

    I’ve measure all wirings and connections, I do not have any shorts or wrong voltages... What am I missing? What else can I measure to identify the source of the problem?
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
    The diodes are backwards to pull down the shut down pin.
  3. Andrei Fejes

    Thread Starter New Member

    Jun 9, 2016
    I have one current going from voltage divider to the SHDN pin, and another coming from GPIO15. So, when ESP is sleeping, I have the voltage dividers keeping the regulator down, when I'm setting the GPIO to HIGH, the regulator activates. I've measured my diodes on the prototype PCB and the flow of current is correct...
  4. dannyf

    Well-Known Member

    Sep 13, 2015
    I don't know anything about your circuit or your pcb design but let me try just logic/common sense:

    1) if the circuit works on your prototype but not on the pcb, wouldn't it be useful to figure out what differences are between the prototype and the pcb? Since we don't have either, you are pretty much on your own.

    2) what does "not give me any voltage" mean?

    3) what does "behaving glitchy" mean?

    I think you have managed to write a lot without saying much. An otherwise quite useful skill but not here.

    My advice to you? Be concise. You may know a lot about your circuit and you may take a lot for granted. Others you need to help you know nothing about your circuit and the little information you give them the little help you get back from them.
  5. Andrei Fejes

    Thread Starter New Member

    Jun 9, 2016
    1. The difference is the additional diode, between the third voltage divider and SHDN pin. The diode brought additionally 0.2V drop, so my circuit did not work
    2. See above
    3. I've made a PCB using etch risistant pen and ferric chloride, and my traces have interruptions. Since the mosfet connection to ground is imperfect, my leds were turning off once in a while

    I'm a beginner in electronics and my terminology and experience are limited. @dannyf - I'll keep in mind your advice.

    Thank you for your advices!