Testing 36V Power Supply with arduino

Hi,

I have a power supply with an output of 36V that I want to test using Arduino. The output of the power supply is connected to circuit with 8A I want to take that output back to the Arduino board to see if there is an output

I don't have a converter or a relay that can work with that voltage, the highest one is for 24V Does someone have an idea for how to solve this problem?

Try a resistor divider. Try 100k and 10k, ie divide by 11, which will map 36V to 3.27V or so. That can be used with an analog input to measure the voltage, or will count as HIGH for a digital input.

Be careful not to directly connect 36V to your Arduino, that will instantly and utterly destroy it. Common the grounds.