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Activate a relay using laptop's parallel port

hrgwea

Apr 13, 2011
2
Joined
Apr 13, 2011
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Hi, guys. I'm new here. Forgiveme if this is too newbie.

I have a relay that I want to switch on using one of the output pins on the parallel port.

This is what I've got:
parallelport.png


The relay is powered by a 5V DC adapter and the transistor should act as a switch.
But i dont know where to connect the parallel port's ground pin.

If I just connect the 5V pin to the transistor's base (like the diagram shows), it doesn't work.
 

Resqueline

Jul 31, 2009
2,848
Joined
Jul 31, 2009
Messages
2,848
Ground to emitter/-5V. Add base resistor (value depends on port, transistor, & relay data).
 

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