Design a on off switch to turn on a LED

[jcheng03]

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]

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]

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]

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]

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]

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]

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