Quote Originally Posted by sirvo View Post
it is working very well since i plugged the heat sink on 7805 regulator..

no more heating at all.. thanks,

mvs sarma.. i would like to do that but i've already bought some 5V relays.. and my supply is 12V ..

Joe S. - yes, that is what i have done.. i've used four bc337 transistors to switch the relays...

Sylvio
Hi, what if? you canadd a resistor series to the coil to limit the current, or you can use the transistor in emitter foller mode where the volage at emitter is less than the voltage at base.