I tried this battery monitoring circuit (https://community.particle.io/t/mea...photon-is-connected-to-4-aa-batteries/18486/3) but it's not working as i thought it would. Battery is 3.3-4V.
My circuit is the same but without the LED. The p-channel mosfet never seems to turn on because the first mosfet is not either?(p-channel's gate is always 3.3V when i bring the trigger line high(3.3V) or low)
Am i missing something?
thanks

 

hi,
What voltage are you applying to the N MOSFET Gate.?
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I mentioned it, it's 3.3V from a microcontroller. Also p-channel mosfet is PMV160UP.

thanks

 

OK,
So what is the N MOS Drain voltage with and without the 3.3V on its Gate.?
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It's always 3.3. So it isn't turning on correct? But why?

 

Are you using a NMOS with a low level Gate turn on voltage.?
Post a datasheet fo the NMOS FET.
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https://gr.mouser.com/datasheet/2/115/DMN2075UDW-10982.pdf

 

OK,
That looks OK.
So it is either a wiring error or a faulty NMOS.
If you can post a photo of the PCB so that we can check it.
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Carefully check the connections to the N-MOSFET:

 

The NMOS, from datasheet, should be fully turned on.

Sure seems like its a wring error or a bad MOSFET....


Regards, Dana.

 

 

For the n-channel, pins 1,2,5 and 6 are connected in the datasheet internally and when i test it with multimeter's continuation tester it's ok.
When i apply voltage to the circuit and measure voltage in pin 1 however, the voltage is 3.3 but the voltage on the rest of the drain pins is 0.

 

hi,
Is it possible to link those Drain pins on the NMOS as a test.?
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I will try.
Also, the drain pins are connected internally (checked) and R20 is connected to drain (pin1) (checked) but not the rest of drain pins!!
how?..

Update: Ok never mind i'm an idiot... bad connection on the board (pin1 was not connected to the pcb). I checked it before but obviously not thoroughly. Sorry for wasting everybody's time and thanks a lot for the help. Next time i'll be more thorough before posting but this time i am in a hurry trying to make this work. Sorry again.

 

hi ir,
No problem, the important point is that you found the problem and let us know.
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