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# 12v Flasher Relay

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#### c4pete

##### New Member
Ok Guys,

I'm new to this board, but I'm seeking some help to build a replacement for my indicator relay in my car. The reason for this is that I want to replace all my bulbs with LED bulbs, but the relay on my car currently flashes at double speed because the load is removed.

Any help is much appreciated!

Cheers,
Pete.

I don't have all of the answer but may offer enough as a start. I recently took a 555 timer, two resistors and one capacitor and made a square wave generator of sorts. Output was either 0 volts or 5 volts - or "off" then "on" since it was a 5 volt supply. The rate was 1 kHz. The circuit came from a site that I found on the internet.

I followed that with a single 7490 configured to divide by 10. It can be configured to divde by other (integral) amounts between 1 and 10. Other than the IC itself no other parts were required. Pin connections determine configuration. With the circuit above I generate 1 kHz divided by 10 or 100 Hz square wave - again - off or on with "on" being 5 volts. Duration of on/off are equal. The 7490 cost less than \$1 (US). Instructions were in a Radio Shack book.

If I wanted a slower rate I could change the values on the square wave generator and/or add several more 7490s to get down to the flash rate desired.

I ran everything off of the 5 volt supply - the 7490 has to run on 5 volts. The output would go to something that would drive a small relay - likely to be a single, low cost transistor. You'd need a 7805 to get the 5 volt supply.

That's one way to do it.

An alternative - program a PIC or BASIC STAMP. This is likely to be much more work. On the other hand, it seems like an excellent beginner's project where the result is actually something you can use every day.

Although this is a fairly good project idea, why re-invent the wheel? Most auto parts store -- and any truck parts outlet -- will have electronic turn signal flashers available. These are considered by most truck maintenance experts to be required exuipment in place of the older electro-mechanical relays, as they are non-load dependent. Consider the differences between the turn signal or hazard warning circuits of a bobtail tractor, a tractor/semi-trailer combination, a set of doubles, and a set of trips....

In the USA, the most popular brand is Grote, and they offer a 2-prong version (P/N 44530) and a three-prong version (P/N 44540), catalog info **broken link removed**. The electronic flashers are plug-in replacements for the electro-mehanicals, but if your flasher(s) are encased in a fuse panel etc., you may want to remote-mount them and use an extender harness to plug into the panel, as these flashers are somewhat larger.

These flashers have been available as optional factory equipment on medium and heavy trucks for years, and when Chevy started sticking a string of signal lamps across the back of their Camaros, electronic flashers were installed as factory equipment there as well.

Your profile doesn't indicate your location, but I'm sure that youo can find these babies or their equivalent somewhere...

I've got a really nice design in a 555 book at home, the clever part is it uses the existing switch and connections to switch it, just like the original one.

Thanks for the replies chaps!

Nigel - this sounds like what I'm looking for - I'd be really grateful if you could scan in the article and e-mail it to me, or maybe just tell me which book, and I could get myself a copy?

Cheers,
Pete.

By the way I'm in the UK in between Liverpool and Manchester

c4pete said:
Thanks for the replies chaps!

Nigel - this sounds like what I'm looking for - I'd be really grateful if you could scan in the article and e-mail it to me, or maybe just tell me which book, and I could get myself a copy?

It's "110 IC Timer Projects For The Home Constructor" by Jules H Gilder, published by Newnes Technical Books.

By the way I'm in the UK in between Liverpool and Manchester

That's not too far away, I'm a few miles west of J29 on the M1.

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