I'm using Arduino to control a SPST N/O Relay. I want to run the relay coil on 12v, so I intend to use an NPN (2n4401) to use the 5v signal to switch the 12v source.
I've set up the NPN on a breadboard to test. I can draw a schematic if necessary, but right now its a 7812 on the 12v line, leading to a resistor/LED and the collector. A 7805 provides the signal on the base of the transistor, and the emitter is connected directly to ground.
Turning 12v on is no problem, but I can't turn it off. I have a resistor from base to ground, I've tried connecting the base directly to ground without the 5V supply connected. Nothing will turn off the LED, only dim it slightly.
What am I doing wrong? Is there a better way to control the relay through the 5v signal?
I've set up the NPN on a breadboard to test. I can draw a schematic if necessary, but right now its a 7812 on the 12v line, leading to a resistor/LED and the collector. A 7805 provides the signal on the base of the transistor, and the emitter is connected directly to ground.
Turning 12v on is no problem, but I can't turn it off. I have a resistor from base to ground, I've tried connecting the base directly to ground without the 5V supply connected. Nothing will turn off the LED, only dim it slightly.
What am I doing wrong? Is there a better way to control the relay through the 5v signal?