How would I make a simple 12v flashing light circuit? - DIY Electric Car Forums

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#1
08-26-2007, 11:55 PM
 KiwiEV Senior Member Join Date: Jul 2007 Location: New Plymouth, New Zealand Posts: 926
How would I make a simple 12v flashing light circuit?

So, how exactly would I make a simple 12v flashing light circuit?

I want the "Low Fuel" light on my dash to flash on and off constantly when the charger is connected. Don't worry about the connection/power side, that part I've sussed out.
All I need to figure out is how to create the circuit to make it flash.
I don't want to use a standard indicator relay as they are too loud and would most likely not work with such a minimal (1 watt?) load.

If no one can figure out a way to do it, how hard would it be to use a simple 9-volt flasher circuit (like a dummy car alarm light) that I could buy from an electronics store. Perhaps I could reduce the voltage using a resistor?

Any ideas?
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#2
08-27-2007, 08:30 AM
 rbgrn Average Joe Join Date: Jul 2007 Posts: 705 Blog Entries: 13
Re: How would I make a simple 12v flashing light circuit?

I remember making those with just a transistor and a capacitor. I'll pull you a schematic.
#3
09-02-2007, 01:56 AM
 Adrian Junior Member Join Date: Jul 2007 Location: Coos Bay, OR Posts: 16
Re: How would I make a simple 12v flashing light circuit?

If you need to use the actual lamp, try this circuit for syncronising LEDs. Replacing the "normal" LEDs with your indicator lamp, and change the 47 Ohm resistor to about (14V - 3V)/15mA = 800 Ohms.

A little more complicated is this 2 wire lamp flasher for lamps under 10W.

Wanna get home brew? Use a 555 Timer Circuit. The output is only good for ~200mA, so you will probably need a transistor (like in the flashing LED circuit) to boost the output current.

MAKE SURE YOUR CHARGER WARNING LIGHT FUNCTIONS WHEN THE CHARGER IS CONNECTED BUT NOT POWERED UP. That way you still get a "my car is plugged in" indication in the event of a power failure or popped circuit breaker!
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1987 VW Cabriolet conversion
114V Trojan T-105, Impulse 9", Zilla 1K, PFC-20 charger
5,000 electric miles

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