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Help with transistoer/switching

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ac86

New Member
i have made a circuit using diagram below and 2x 4017. All is working fine with LEDs connected directly to the output of 4017 and to -ve via resistor.

problem is though, the diagram has LEDs between +ve and transistor, and transistor straight to -ve. What i need is something that will switch the +ve, since -ve of LEDs will always be connected to -ve. What parts do i need?


http://www.electro-tech-online.com/attachments/firetrucksch3-gif.25138/

Thanks
 

crutschow

Well-Known Member
Most Helpful Member
You can add two PNP transistors, such as a 2N2907 or similar, to the circuit.

Connect the bases of the 2907's to the collector of the respective 2N2222's through 1KΩ resistors. Connect the 2907 emitters to the +ve. Connect the 2907 collectors to the LEDs connected to -ve.
 

audioguru

Well-Known Member
Most Helpful Member
Why not make the circuit the way it is shown?
If you change the transistors to be emitter-followers and use low voltage red LEDs then the LEDs can be connected to ground.
 

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