3 replies to this topic

[stormintrooper]

Basicaly i want to use my circuit simulator to design my own flasher unit....either for the indicator unit or hazard....preferably the indicator

Only thing holding me back is i have no idea what the wiring diagram for the flasher itself is...so im wondering if anyone out there knows and can help me out...and yes i have tried google

[dklawson]

There are obviously plenty of off-the-shelf flashers out there for both incandescent and LED bulbs. Designing your own flasher will require a bit of time and is certainly going to cost more than an commercial part. However, I'm sure you have a reason why you want to build your own.

I did not find any schematics to send you but I would like to provide you with a couple of links and a text explanation for the electro/mechanical type flashers.
See this picture which shows what's inside most electro/mechanical flashers:
http://www.geocities...es/flasher3.jpg

See this link for a Lucas specific set of pictures and discussion:
http://www.mgb-stuff...uk/flashers.htm
The MGB link should prove very informative.

Succinctly, the traditional flasher is an electro-mechanical relay.
Inside will be a set of normally closed contact points.
The element holding the contacts together is a piece of bimetallic metal wrapped with a resistance heating wire.
The heating wire has low resistance and is in series with power going to the lamps.
Power enters the flasher on one terminal when the turn signal or hazard switch closes.
Power passes through the closed points, then through the resistance wire, and finally out to the terminal supplying power to the lamps.

Since the points are normally closed, current will immediately flow through the contacts, through the resistance wire, and out to the lamps when you activate the turn signal or hazard switch. This in turn quickly generates heat on the resistance wire which causes the bimetallic strip to bend... opening the points. When the points open, current no longer flows through the resistance wire which allows the bimetallic strip to cool and the points close again. The amount of current flowing affects how fast the resistance wire heats up and therefore... the flash rate. If a bulb burns out the flasher will typically flash slower, or not at all.

In the picture link above you can see the resistance wire looped around the bimetallic element, you don't really notice the contact points. On the MGB link you will see both the resistance wire and the points quite clearly.

I assume you'll be designing an electronic flasher so you'll be handling this a bit differently.

Edited by dklawson, 08 January 2009 - 12:58 AM.

[stormintrooper]

Cheers for that...and yes i want to try and design an electronic flasher

i know these kits are readily available to buy but i wanted to see if i could practicaly design and make my own so that i can run whatever bulb i like...cheers..if you like i can show you any designs i come up with...that is assuming i can design one that works

[dklawson]

OK, I understood you had a reason that you wanted to undertake this task. Perhaps you can design in a variable flash rate or use a memory chip to strobe the lights in Morse code. There are lots of possibilities.

Doing this with electronics will be a bit different than the electro-mechanical method. Look carefully at your car's wiring diagram to see where the flasher is relative to the turn signal switch. I can only comment on the early cars, yours may be different.

The flasher input terminal has power supplied to it anytime the ignition is on. Its points are closed. When you activate the turn signal switch, the switch is connecting the lights on one side of the car or the other to the output side of the flasher. Think of the turn signal switch as a single-pole, double-throw toggle switch with a center-off position.

You will need to give some thought to how you will use the turn signal switch to activate your circuit and still have the switch connect the lights on the car to the power source. When you get further into this be sure to let us know what direction you take.