I want to control a 12 V relay using an Arduino 5 V signal, but due to some unknown reason the relay does not work. I am using a BC548 transistor as a switch for relay. Please suggest where I go wrong.
closed as off-topic by Juraj, sempaiscuba, VE7JRO♦, MatsK, Greenonline Feb 21 at 17:26
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "This question does not appear to be about Arduino, within the scope defined in the help center." – Juraj, sempaiscuba, VE7JRO, MatsK, Greenonline
If it's working with 12v on the input but not 5v, it sounds like the base resistor value (which is missing from the diagram) might be too high. A value of around 1k should ensure the transistor is fully switched on.