HELP! Arduino failing to measure 600VDC through a 150 to 1 Voltage divider

Hello - I’m really bummed out that after 6 months three separate Arduinos DUO have stopped reading analog signals from a 150 to 1 Voltage divider shown as R1 and R2 in the attached photo. Any ideas what’s going on?

I have two units at one location and a third unit at another location.

They were working perfectly before they stopped!! (The arduino functions as normal spitting out data at 9600 baud through a 2kV black box isolation module to the LabVIEW data logger computer).

But the Voltage channel is reading zero Volts. I’ve tried:

  • Resetting the unit
  • Reprogramming the board
  • Unplugging the USB cable and putting it back in again

The systems are 3,000 miles away from me and now I am going to have to purchase an expensive plane ticket to go trouble shoot them.

Yeah, my stuff always works perfect before it doesn't. Bet you did not include anything to limit the voltage to the Arduino pins.

And I see a black wire stringing around connecting everything in a daisy chain, not all connected to a common ground point.

And I see crimped terminals on the wires. Is this installation somewhere that has high humidity? Crimped terminals can and do develop high resistance.

Paul

It looks to me as though you have a non-soldered joint on the red wire between R1 and R2, (at the R1 end).

If that is the case, then R2 is not in circuit, and you are then putting 600V on to the Arduino input through R1. Depending on the value of R1, you may or may-not have damaged the input.

Note, that if would have been safer (for the Arduino), If you had connected the red wire going to the Arduino input on to R2's terminal. In that case a non-soldered joint on either wire connected to that terminal would just cause the voltage to drop to zero,and not cause any damage.
Under no-fault conditions these two different ways of wiring the circuit up are exactly the same, but if there is a dry joint, then they behave completely differently.