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Headlight Flasher


Valic

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This project?
http://www.electronics-lab.com/projects/automotive/003/index.html

The current rating of the relay contacts must be at least as high as the headlamps' current plus more, since a cold incandescent lamp draws up to 10 times its operating current.

The current rating of the transistor must be high enough to drive the relay's coil.
The value of the 1k resistor feeding the base of the transistor must supply enough base current.

I recommend adding a reverse-connected diode across the relay's coil to avoid breakdown of the transistor and 555 IC due to the inductive voltage spike.

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It’s better to use a semiconductor switch for this; the halogen lamps (and the relay) will suffer badly if turned on and of repeatedly. If repeated very often it might be les harmful since the filament is still very hot for the next pulse.

Just my two cents! ;)

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  • 6 months later...

I thought car headlights are 60W and draw 5A to 6A when hot, and draw 50A to 60A when cold. They are turned on by a big strong relay. A 3A relay would be a tiny little thing and wouldn't even be needed since the switch could turn on a little 3A light without a relay.

If I select a Mosfet that I can buy here in Canada, could you get it? I don't know which parts you can buy.

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