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transistor switching

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New Member
hello everyone...i very new at electronics, and i would just like to ask if its possible to have a circuit switched by a transistor that would normaly be closed. and when a current flows to the base the circuit woul open. the input power would be 5 amps 12v. i realy need your help for a project. thank you


Well-Known Member
5 amps is pretty hefty

what about using a relay?
a PNP transistor would do the switching to control the relay.
Is the voltage 12v AC or DC?
If AC then a triac would do the switching of 5amps
If DC then an SCR could be used but additional circuerty woul be required to turn off
PNP transistor
current on base = off
base grounded = on
NPN transistor
current on base = on
base grounded = off

wold help with more info.


New Member
Reasonable circuit but Current to load equals 5 amps and when does it reacvtivate circuit?.

think outside the square and square that


Well-Known Member
need more info

here is a basic 12 volt coil/400 ohm being switched by a 2n2222 transistor.
your info is no real clear
what is turning the transistor off and on??
wire the DPDT relay so when the transistor is enerigized the relay contacts are open and visa versa.
based on info this is it.



Well-Known Member
Most Helpful Member
There is no transistor. There is a door that opens and closes.

Transistors either turn on or turn off, they do not open and close.
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