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

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Can opening and closing switch turn on and off 10 ma relay
213876-37ca1887f27360392fe41e7e88c748a7.jpg
 

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  • #2
berkeman
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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?
 
  • #3
eq1
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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....
 
  • #4
berkeman
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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)... :wink:
 
  • #5
Baluncore
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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.
 

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