Measuring the voltage of Jetson Nano's own power source

Hi everyone ! I am doing a module to display the battery voltage which supply the Jetson Nano.
Here’s a quick scheme of the circuit :

The Jetson Nano is supplied by two 12v batteries in series with a 24->5V DC converter.
And the input of the ADC is one of the battery.
The problem that I encountered is that there is only 1s in output, so the code print 15v.
I tested my code with a third battery which is not supplying the circuit and It worked.
Thanks in advance for your help !
ps : I used an ADC MCP3001 I/P

Your diagram is somewhat hard to understand.
Is there common ground between the ADC and the battery?
Have you verified the input voltage at the ADC using a multimeter or scope?

Also, as an aside: Your circuit will draw several mA of current while connected, which will somewhat reduce the runtime of the battery. The high current will help the ADC when it’s sampling to not affect the voltage it reads, but you can easily increase the resistances to something like 10 kOhm on the bottom and 22 kOhm on the top, and maybe even add another factor 10 to reduce current draw. All you need to do is buffer the input signal to the ADC with a capacitor. A ceramic 1 uF capacitor should do fine.

1 Like