relays turned on and off alternately

[ChevyLT1Camaro94]

Okay so i need to make 2 relays alternate on-off, off-on, on-off...etc. about 1 flash per second. its to make my high beams alternate like a wig-wag on an emergency vehicle. i have a bunch of radio shack transistors, and i was thinking some sort of led flasher circuit might work. or a circuit with a 555 timer. i would like to stick to radio shack parts for personal reasons. any help is appreciated.

12v 30 amp relays need to be turned on and off alternately

 

[Jon Raylaw]

I've been down that road

understand that you are making things difficult for yourself.

I purchased a wig-wag adapter from JCWhitney a few years ago, it installed like a dream, and even allows me to control my high beams independently of my standard headlights. Which on my lowered '02 Z28, is wonderful at night while racing through farm country.

Other than that you could hook up a standard flasher unit ($1.25 from Autozone) to a relay or two in this configuration:
**broken link removed**

I was going to use this circuit for another purpose, but have not gotten around to it yet. Sorry to all, as I no longer have the original posting location for the circuit attached.

 

[blueroomelectronics]

It's also illegal unless you're an emergency vehicle.

 

[Jon Raylaw]

RE: relays turned on and off alternately Reply to Thread

Details Details!

If the parking brake is engaged it is legal in my state.

 

[Andy1845c]

As Bill says, it is illegal to have flashing headlights on a public road.
Please don't use them on the street!

Making a circuit is fairly simple if all you want is a simple L-R-L-R pattern.

A 555 timer in astable mode will work, as would the classic 2 transistor multivibrator.

A 555 will not drive a large relay. Use the 555 to drive a darlington or MOSFET and drive the coil of the relay with that, at 12v. Don't forget a freewheel diode across the coil to keep the coil on the relay from blowing out the transistor.

Here is a alternating flasher circuit using 3 555s
alternating flasher circuit diagram - Note the freewheel diodes. They are driving small relays. I don't know the specs on yours, but I don't think a 555 can supply enough power to turn one on without help.

You can also just use 1 555,

Here is the classic 2 transistor astable multivibrator: **broken link removed**

Basicly, you can switch transistors insted of LEDs with any of these and use the transistors to switch your relays.