Another pair of eyes needed

My project consists in two 12V car batteries, B1 is only measured via voltage divider through ADC of Arduino.
B2 is measured in the same way but is also feeding switching regulator that provides 5V to Arduino and current sensor.

The load to sense by the current sensor is a 12 Volts motor (a few Amps) power by B2.

There are other input and output devices (not showing on my drawing) but basically LEDs and switches.

The motor and batteries sensing are all OK as well as all other I/Os but when the motor starts and stop it is falsly triggering other I/Os

How can I resolve this?

The problem is likely caused either by transients on the power line (add more decoupling capacitors) or transients on the ground due to the motor ground current going through the circuit ground (the motor should have a separate ground return to the battery).

What do you mean "false triggering"?

You probably have motor noise. Look here;
https://www.pololu.com/docs/0J15/9

crutschow said:

The problem is likely caused either by transients on the power line (add more decoupling capacitors) or transients on the ground due to the motor ground current going through the circuit ground (the motor should have a separate ground return to the battery).

What do you mean "false triggering"?

Click to expand...

I have an I/O that get's triggered from a transistor switch (water sensor) when the motor was stopping that I/O was triggering although no water detected, however I have rewired the ground from the motor directly to the battery as you suggested and more testing will confirm but it appears to behave much better.

4pyros
Thanks for the link, I don't really want to mess on the motor's side as it is a sealed bilge pump.

If I was to add a decoupling cap would a 0.1u be best placed in parallel next to D1?
Edit: and maybe another one at the Arduino supply?

lilimike said:

I have an I/O that get's triggered from a transistor switch (water sensor) when the motor was stopping that I/O was triggering although no water detected, however I have rewired the ground from the motor directly to the battery as you suggested and more testing will confirm but it appears to behave much better.

4pyros
Thanks for the link, I don't really want to mess on the motor's side as it is a sealed bilge pump.

If I was to add a decoupling cap would a 0.1u be best placed in parallel next to D1?
Edit: and maybe another one at the Arduino supply?

Click to expand...

Yes and yes

You can just use a software switch debouncing/digital-filter routine to reject the false triggers.

dougy83 said:

You can just use a software switch debouncing/digital-filter routine to reject the false triggers.

Click to expand...

My issue was not related to a bouncing switch, I had the motor on one sensing ADC trigger another I/O but I believe rewiring the ground fixed the problem.

lilimike said:

My issue was not related to a bouncing switch, I had the motor on one sensing ADC trigger another I/O but I believe rewiring the ground fixed the problem.

Click to expand...

It's better to do as you've done and remove the source of the interference. The debounce/digital-filter is useful when you can't remove the source of the interference.