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jcheng03
Joined: 11 Jul 2006
Posts: 10
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 11 Jul 2006 7:37 Design a on off switch to turn on a LED |
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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?
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stefano.delfiore
Joined: 02 Apr 2006
Posts: 37
Helped: 5
Location: Italy
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| 11 Jul 2006 12:57 Re: Design a on off switch to turn on a LED |
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| jcheng03 wrote: |
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!
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jcheng03
Joined: 11 Jul 2006
Posts: 10
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| 12 Jul 2006 4:57 Design a on off switch to turn on a LED |
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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??
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stefano.delfiore
Joined: 02 Apr 2006
Posts: 37
Helped: 5
Location: Italy
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| 12 Jul 2006 7:23 Re: Design a on off switch to turn on a LED |
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| jcheng03 wrote: |
| 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
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jcheng03
Joined: 11 Jul 2006
Posts: 10
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| 12 Jul 2006 9:54 Design a on off switch to turn on a LED |
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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???
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IanP
Joined: 05 Oct 2004
Posts: 6361
Helped: 1509
Location: West Coast
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| 12 Jul 2006 10:13 Re: Design a on off switch to turn on a LED |
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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
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jcheng03
Joined: 11 Jul 2006
Posts: 10
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| 12 Jul 2006 11:06 Design a on off switch to turn on a LED |
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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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