Driving an enable pin low via arduino

Question

I have the following V regulator, that has an enable pin that i'd like to control via an arduino: https://www.pololu.com/product/2582

I tried using a relay (ELEGOO Relay Module 4 Channel DC 5V with Optocoupler for Arduino) with the following pins:

Relay pin1: 0v of 24v battery

Relay pin2: enable pin of pololu v regulator

I then enabled the above relay via an arduino digital out pin.

However it seemed to have no effect, the regulator never shut off. If i manually join the two relay pins, pin1 and pin2 the regulator does shut off though .. A and B in picture.

Any ideas why the relay is not working via the arduino? or should it work? am i doing something wrong? I am not too familiar with pull up or pull downs..

I have since disconnected everything and put it away, i am just looking for theory help, confirmation it should wotk. I managed to get the relay working for leds at the time .. would the fact that current flows in the other direction for this pull down relay setup, be my issue and that i should swap around wires A and B?

(As a workaround i used a relay to switch on or enable the 24v Vin line out from the battery instead, that seemed to work okay..)

Answer 1

Unless you require galvanic isolation (and it's highly unlikely that you do) you don't need the relay.

The EN pin only needs to be above 1.3V to turn the unit on, or below 0.9V to turn it off. The voltage range is anything up to 30V.

Just connect the EN pin directly to an Arduino IO pin. Write a HIGH for on and a LOW for off. And of course connect the grounds together.