@felmue
thanks Felix for your help I now have it working... something was going wrong between moving from USB to battery.

Hi,
Appreciate any help on this... I'm trying to switch a relay on/off on my Core Ink, and it's working fine while the Core Ink is connected on USB, but as soon as I unplug, it stops. Presumably this is because I only get 5V supply when on USB? How can I drive a relay from the battery on board the Core Ink? is there any 3V or 5V output from any port that should work when on battery?

Thanks,
Anthony.