Control LED by car ignition. - Electronic Circuits Projects Diagrams Free

tim_l_012 · 3rd January 2004, 01:43 AM

Hi All,

i need a simple circuit to switch off a circuit when current is passed through it.

The 12v comes from the car battery, and I would nick 12v from the cigarette lighter/radio wire. The radio only comes on with the ignition.

i have a flashing LED setup, but I need it to turn off when the ignition is on.

If you could provide any help that would be excellent.

Thanks in advance,

Tim.

john1 · 3rd January 2004, 01:56 AM

take its ground to the ignition.
that should do it.

tim_l_012 · 3rd January 2004, 01:59 AM

Hmm I don't understand that one..

I'm a bit of a beginner so you might have to explain a bit.

What do you mean?

Thanks in advance,

tim_l_012 · 3rd January 2004, 02:13 AM

My mate suggested something like a NPN transistor..

I have been looking around and a NAND gate seems like something simple.. are they hard to implement?

If so how would I connect them?

Thanks in advance,

Tim.

tim_l_012 · 3rd January 2004, 02:45 AM

Just thinking back to a sort of similar post I had ages back, If i just remove the other LED, should this circuit in this post be ok?

Remembering that its 12v instead of 5v though, my LED can handle from 3v to 15v.

http://www.electro-tech-online.com/viewtopic.php?t=1320

Thanks in advance,

e · 3rd January 2004, 04:07 AM

you can do it with a small relay as well, coil IGN and ground, NC -power to LED and common to supply

Eclipsed · 3rd January 2004, 05:50 AM

I think what he meant was, on most vehicles the ignition is a ground when the key is off.So put a constant power to the positive side of the led and run the negative to the ignition, then the circuit is complete when the ignition is off.I would put another diode in there too, some of the vehicles power circuits could become a ground if a fuse blows, which would reverse the LED voltage.

seeker · 3rd January 2004, 10:22 PM

Hi Tim,
maybe try this
http://www.radioshack.com/product.as...5Fid=276%2D308

Diode is 1n4001 or similar

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3rd January 2004, 01:43 AM	(permalink)
tim_l_012	Control LED by car ignition. Hi All, i need a simple circuit to switch off a circuit when current is passed through it. The 12v comes from the car battery, and I would nick 12v from the cigarette lighter/radio wire. The radio only comes on with the ignition. i have a flashing LED setup, but I need it to turn off when the ignition is on. If you could provide any help that would be excellent. Thanks in advance, Tim. __________________ Tim.

3rd January 2004, 01:56 AM	(permalink)
john1	take its ground to the ignition. that should do it.

3rd January 2004, 01:59 AM	(permalink)
tim_l_012	Hmm I don't understand that one.. I'm a bit of a beginner so you might have to explain a bit. What do you mean? Thanks in advance, __________________ Tim.

3rd January 2004, 02:13 AM	(permalink)
tim_l_012	My mate suggested something like a NPN transistor.. I have been looking around and a NAND gate seems like something simple.. are they hard to implement? If so how would I connect them? Thanks in advance, Tim. __________________ Tim.

3rd January 2004, 02:45 AM	(permalink)
tim_l_012	Just thinking back to a sort of similar post I had ages back, If i just remove the other LED, should this circuit in this post be ok? Remembering that its 12v instead of 5v though, my LED can handle from 3v to 15v. http://www.electro-tech-online.com/viewtopic.php?t=1320 Thanks in advance, __________________ Tim.

3rd January 2004, 04:07 AM	(permalink)
e	you can do it with a small relay as well, coil IGN and ground, NC -power to LED and common to supply

3rd January 2004, 05:50 AM	(permalink)
Eclipsed	I think what he meant was, on most vehicles the ignition is a ground when the key is off.So put a constant power to the positive side of the led and run the negative to the ignition, then the circuit is complete when the ignition is off.I would put another diode in there too, some of the vehicles power circuits could become a ground if a fuse blows, which would reverse the LED voltage. __________________ Eric.