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Design a on off switch to turn on a LED

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jcheng03

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I have a quiz question. I have p-channel and n-channel bipolar transistor, resistor, a LED, 2 tact push buttons, power source.
Need to design a circuit when i press the On button once and release, the LED will turn on. When I press the Off button once and release the LED will turn off?
Any idea? Please help?
 

stefano.delfiore

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jcheng03 said:
I have a quiz question. I have p-channel and n-channel bipolar transistor, resistor, a LED, 2 tact push buttons, power source.
Need to design a circuit when i press the On button once and release, the LED will turn on. When I press the Off button once and release the LED will turn off?
Any idea? Please help?

You should try this simple basic circuit, it use an pnp and a pnp bipolar transistor.
Bipolar transistors don't have channel!
 

    jcheng03

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jcheng03

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Thanks for your help. However, it looks like this will work if the keys are permenantly switch on/off. if we use the push button tact STSP momentary switch. It fails to work? Please advise or any other comments??
 

stefano.delfiore

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jcheng03 said:
Thanks for your help. However, it looks like this will work if the keys are permenantly switch on/off. if we use the push button tact STSP momentary switch. It fails to work? Please advise or any other comments??

Sorry for the symbol that I used for S1 and S2.
S1 and S2 are buttons not switches.

stefano
 

jcheng03

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The quiz question is to use the tact push button STSP, when press once and release, so only one pulse generated. How to design this? like a state machine???
Flip flip like?? any idea???
 

IanP

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Circuit suggested by Stefano does exactly that: one short positive pulse on the START and the LED is ON, one short pulse on the STOP and the LED goes OFF ..

Regards,
IanP
 

jcheng03

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After i carefully review the circult, I understand now. Thanks again. I like this site very much....
 

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