I have a question regarding the configuration described in: http://www.ucapps.de/midio128/relay_example.pdf There is only a single ground on the ULN2803, should this be used to ground both the lower voltage switches (from the DOUT) and also the higher voltage switches (shown as relays in the example, but lamps in my case)?  Can different voltages share the same ground in this way (apologies for such as basic question). James