I have a project that boils down to a arduino connected to an 8 way relay.
I have made a power supply for using a bridge rectifier from an old tv, a 3300uF capacitor and one of these: .
It takes 24VAC and puts out 5VDC and some of the 24VAC goes to triggering solenoid valves attached to the relays.
It all works fine while the USB cable is attached to the Arduino, even if I also have the arduino connected to my power supply at the same time.
But as soon as I remove the USB cable, and run the device as stand alone, the relays won't trigger.
I can see the function that does the digital write on the relay pin being called because I have debug info going out a HC05 and into TeraTerm running on my PC.
Can anyone explain this and how I might resolve it? I have absolutely no idea why this is happening.