i have an app, with a avr with some output's that switch from tristate to gnd
avr its on 5vdc but an "external circuit" works at 12vd with common gnd to avr
goal is the "external circuit" to control a relay followed by out (tristate/gn -> on/off relay)
have try with transistor bc548 driving relay but because even at tristated output some small current pass, output of transistor has some kind of analog out , and relay remain latched
can somehow this controled by simple transistor, or need some kind of buffered out , from avr ?!