I'm trying to make a pulsating (blue) LED effect for my motorcycle using ~30 to 50 LED's in a 3-by-3 parallel array, resistors, fuse, switch, etc, off the bike battery. I've got the LED's & correct resistors soldered. My question is, "how do I go about the pulsating process?" I've been reading about 555 timers and darlington's transistors, but I'm not sure how to wire these or which models to buy (off ebay? radioshack? ??). A schematic and explanation would be ideal, and beyond my expectations. I'm really not picky about how these pulse, just so long as they DO. ANY help or advice is greatly appreciated. THANKS

I WILL NOT BE USING THE LED LIGHTS WHILE DRIVING. They are legal if parked in a parking lot. Hence car/bike shows...

fyi: Battery is 12-volts, unsure of ampage (6-12 amp hrs)

Are you aware that operating the light on the road might be illegal where you live and that such a modification would invalidate any warranty?

In Canada you would be fined for impersonating a snow plow. Only snow plows are allowed to have flashing blue lights.

Originally Posted by audioguru

In Canada you would be fined for impersonating a snow plow. Only snow plows are allowed to have flashing blue lights.

So, it was a snowplow chasing me that night outside Cornwall. I always wondered how I outran him.

In the U.S. I believe many states allow blue lights only on emergency/police vehicles. Impersonating a police motorcycle would likely be frowned on by the authorities.

I went through a speed radar trap in Pensylvania in the middle of the night far away from any city at 130mph. The cop couldn't take me so far back to his office so warned me that I must pay the huge fine by mail. He said the US has an agreement with Canada for collecting fines. I never paid and they never came after me.

Usually whenever the police chase me they pass to catch somebody else.

If that had been in the UK you would have been banned.

As you're a foreign national, I don't know what would have happend, they may have made it illegal for you to drive in this country.

In Canada we have had "daytime running lights" since 1989. Cars in the shadows of trees and at dawn and at twilight are visible.

But I think it is out of control. Some cars and trucks made by Chrysler have high beams at full brightness and are blinding when coming at you at dawn, twilight or on a cloudy day. My car has the turn signal lights dimmed during the day. They can be seen but are not blinding. Other cars have the low beams dimmed during the day

Oriental people here drive at night with the parking lights and the dimmed (except for Chrysler) daytime running lights on. They can't see the road at night and other drivers can hardly see them. They don't have a clue.

Then we get the drivers who have their very bright and blinding high beam lights on all the time. They also don't have a clue.

Use an astable 555 timer to flash the lights at the desired frequency.

There might be a problem with that idea as blue LEDs have a higher forward voltage.

You can buy flashing blue LEDs, just put one in series with two other non-flashing blue LEDs and a series resistor.

OK, so you've got your LED's, plus some way of controlling them, ergo a darlington transistor.

First things first, if the battery on your bike is 12V, unless you want to get into the weird world of switched mode power supplies then thats your maximum voltage. This means that if you put LED's in series, you're looking at a maximum of 3 + current limited reisistor. I suspect the forward voltage of most blue LED's is >3V so to be safe I would put two LED's in series, along with a resistor.


The value of the resistor you choose depends on the voltage across the LED's, the voltage of your bike battery (12V but it WILL vary quite a bit) and how bright you want the LED's to be. Some larger LED's can take up to 300mA, but the smaller 5mm ones will take about 20mA. I wouldn't go over 20mA.

Heres a quick example.... put two led's in series, along with a 330-680 ohm resistor. measure the voltage across the resistor. Forget about how bright the LED's look for now, if they are bright, then thats fine, if not, then you can change the resistor value.
Resistor value = voltage across resistor/ current you want for LED's.

So for 20mA (15mA would extend the LED life) R = Vr/0.02.

here's a quick schem I've drawn up so I don't go on forever explaining bits. Its a 'rough' schematic, many values left out, just so you know the sort of thing you'd need, and how everything fits together.

Thats the 'true' DIY approach. There are other ways, like buying a premade thing for flashing LED's and modding it. 30-50 LED's is quite a lot, considering many of them are narrow viewing angle, that means you'll be kicking out a hell of a lot of light in one direction.

If you need anything else, just ask.

Bleteeth

Edit: I'm an idiot....12v/3 = 4. You could have THREE LED's in series. You'd need a lower value resistor. Lower power disappation in the resistors and transistor for the given number of LED's.

You could always buy a premade setup.
http://streetglow.com/site/motorcycle.index.php