Can this configuration ever work? (battery and transistor to turn on a relay)

[John1397]

Main Question or Discussion Point

Can opening and closing switch turn on and off 10 ma relay

 

[berkeman]

Can opening and closing switch turn on and off 10 ma relay
View attachment 230796

Not as drawn, but with a couple more resistors (or just a different configuration) and a diode, it can work. Have you tried using Google Images to find such circuits? Where did you get this one?

 

[eq1]

Where did you get this one?

I think it's just misdrawn. NPN is supposed to be a PNP. I personally wouldn't do it that way but with the correct PNP it should work....

 

[berkeman]

I think it's just misdrawn. NPN is supposed to be a PNP. I personally wouldn't do it that way but with the correct PNP it should work....

Ah, interesting thought! At least it will work once with the PNP (and no diode)...

 

[Baluncore]

The relay coil is an inductor so it needs a parallel power diode to prevent the inductive reverse voltage spike that will otherwise destroy the transistor when the switch turns off and the magnetic field collapses.