I started playing around with arduinos recently and I found a wierd problem.
When I push code to the arduino I can get it to work as I wish, no problem. But when I unplug it and set it to run on external power everything messes up.
For reference I have a relay that is supposed to turn on when a soil moisture porbe reads below a certain value, but only for a couple of seconds. This works fine on the PC power, buit when I hook it up to my 12 V power supply the relay is permanently on.
Any help appriciate.