Detect if there is current in a DC 100v circuit at .1 amps

Hi all,

I have been reading and trying to detect if there is current in a dc circuit, epicly failing so far :confused:
I am using a constant current led driver :

to feed 6 cobs that have a 32V fwd voltage (all in series). The driver is turned on/off using a relay on the AC side and in order to add an extra layer of "security" and trigger an alarm if the relay is not in the correct state I want to check the DC side after the 6th cob for current and get a Current/No-Current reading.

After the 6th cob I am left with aprox 90v at a current that goes from .7 amp to .1 amp if the dimming is at it's highest.
I tried using the ACS712 5A version sensor breakout board but the reading is super shaky plus the definition is not good enough so the reading is petty much the same if 0.0 or 0.1 which defeats the purpose. I even tried doing 100 readings and averaging the results to see if there was a difference, it improved, but still I get a bunch of false positives.

I read about voltage dividers but even if I get to pull the voltage down to 5v to avoid frying the arduino I still have too
high of a current thus I would keep frying the arduino.

Any ideas on how to solve this ?

Please keep in mind that I am an electronics noob, not afraid to try out wild things, but still a noob.


The voltage should be almost-constant, even when dimming so it would be easier to check the voltage (with a [u]voltage divider[/u]). The resistances in your voltage divider should probably add-up to 100K or more because you've got high voltage and you want to keep the power (and heat) in the resistors to a minimum.

It would also be a good idea to add a [u]over-voltage protection diode[/u].

So... If circuit is broken and no current flows, the voltage should jump-up as it tries to push constant-current through infinite resistance. And if the power supply dies, the voltage will drop.