Headlight question

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by redduck &raquo;</TD></TR><TR><TD CLASS="quote"> I went to a Radio Shack looking for some 12VDC white LEDs... That place just isn't what it used to be. They couldn't help me with the diodes, but I am thinking if I needed any cell phone accessories, I was in the right place!</TD></TR></TABLE>

The nature of LEDs will prevent you from ever finding a White 12V LED. The only way to get an LED to function at 12V is to add resistors. The COLOR of the LED determines the necessary voltage. a red led will burn at about 1.7 volts. a white or blue LED will need 3 to 4 volts. This is partly responsible for and also a product of why you see "4 little LEDs in one" You want a yellow LED (say for a turn signal), yellow LEDs use about 2.1-2.3 volts, put four in a series and you have a 8.4 to 9.2 requirement. Use resistors to drop off the 12volts to 9.2 (dropping 2.8 volts). Most stor bought LEDs run on 20 milliamps. Apply the following formula to determine R (R= the resistance in Ohms):

R = (12 - 9.2) / 0.020(amps, not milliamps here)

SO,

To run ONE super bright white LED at 3.4 volts ( i looked it up this time) from a 12V power supply (your motorcycle) you would need to truncate about 20% of the available voltage to accomodate fluctuations without making the LED 'flake out'.

so, 10V power supply.

10 volts - 3.4 volts = 7.6 volts.

7.6volts/ .020 = 380.

You'll need a resistor of 380 ohms, or a few that add up to 380, wired in a series.

Good info... It's been a while since I've had to apply Ohm's law to anything!!! I found a site that sells individual diodes. They have some white 3MM diodes that are 3.6 to 4VDC @ .020 to .030 amps each. So, I guess if I wired four to a cluster in series, I would at least be OK with no resister. Actually, it would take 14.4 volts to meet the 3.6 volts per diode, so it may be better to go with the three using a 60ohm resistor...

Here's an interesting calculator I found while looking
http://ourworld.compuserve.com...d.htm

here's the website I will probably source the diodes from, if I ever get around to it!!
http://www.theledlight.com/


Modified by redduck at 3:38 AM 2/7/2005

Hell, I'm just glad I was able to use something I learned... that's rare!

Be sure to note, when you are powering up your LEDs that all of the LEDS wired in a series will only draw only the Amperage of one LED, but the voltage is added together. like 4 white LEDs at 3.4 volts and 20 miliamps wired in a series will need 13.6 volt stable power supply but only 20 milliamps. as opposed to 4 white LEDs wired in parrallel, they'll need only 3.4 volts, but 80 milliamps.

I know what you mean... It was 1984 when I went through the Navy's basic electronic schools. I had to clear out the cobwebs a little, but it all comes back to you!

I have the parts I need. I found four 3.6vdc 20ma white LEDs. I did pick up a few resistors, but i think I am going to wire four of them in series without any additional resistance. Given that the rectifier/regulator puts out a nominal 14vdc anyway, I think i should be fine. The one thing I have to work out is how to mount the LEDs on a board that can still use the stock light socket. I have a decent idea, and will work on it over the next week or so. I'll post a pic if it works and looks OK.

While we are on the subject of headlights, does anyone know of any sites (prefer uk) where i can get one of the 999 style headlight fairings for a 02 supersport i.e.

cheers

OK... I have discovered that there are no such thing as "white" LEDs. These are sort of white, but still a hint of blue. I got them at radio shack. Since I didn't have a need to buy in bulk, the diodes weren't exactly cheap. The whole project was around $25.00. A little spendy for a home made light! The results are so, so. Here are a few pics. You can decide for yourself if it is worth the trouble!

Kind of a hack-job, but it is pretty secure.




Pilot only


As you can see, when the head light is on it mostly drowns out the pilot

Very cool. Looks VERY similar to what I have. Except you got to bond with your bulb. Fun stuff isn't it? Now if I can just find the right LED turn Indicators, it will be an LED complete bike.
FWIW, I passed a couple of LEO's today and no problems at all with the light. Granted it was daytime, but the headlight drowns out the pilot bulb so much, I don't think it will be a problem at all at night.

Well, if burning your fingers with a soldering iron can be considered bonding, I guess the light and I are pretty much inseparable now!

See how lucky you are? Any time you get battle wounds from DIY mods, it makes your experience much more memorable.

Does the light sit in the pilot housing okay?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CaliDuc &raquo;</TD></TR><TR><TD CLASS="quote">Does the light sit in the pilot housing okay? </TD></TR></TABLE>

It fits right in. I made it pretty close t the stock bulb's dimensions. The cluster of 4 diodes is a little larger in diameter, but no problem fitting it through the housing.

It survived a pretty spirited ride today. I think I gained .0001 HP!!!! Less load on the electrical system from the diodes!!!

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CaliDuc &raquo;</TD></TR><TR><TD CLASS="quote"> See how lucky you are? Any time you get battle wounds from DIY mods, it makes your experience much more memorable.
</TD></TR></TABLE>

That is what I keep telling my wife everytime she has to run into the garage with papertowels and bandaids. The satisfaction of DIY.

Redduck:<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by redduck &raquo;</TD></TR><TR><TD CLASS="quote">It survived a pretty spirited ride today. I think I gained .0001 HP!!!! Less load on the electrical system from the diodes!!!</TD></TR></TABLE>

You noticed that too? I thought it was just me.

TnDuc:<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TnDuc &raquo;</TD></TR><TR><TD CLASS="quote">That is what I keep telling my wife everytime she has to run into the garage with papertowels and bandaids. The satisfaction of DIY.</TD></TR></TABLE>

You know you are REALLY good at the DIY stuff when the wife calls an ambulance for a 'standbye' when you tell her you will be in the garage.