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post #1 of 6 Old Jul 18th, 2007, 10:34 pm Thread Starter
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Question Need help with electrical project...

Need some help with a side reflector project......I know I can buy a kit but I like to tinker so I mounted 6 3volt red leds into the reflector and soldered them in a parallel configuration and put 3volts to it and it light up perfect. Now the problem. How do I drop the 12volt on the bike to 3volts......Resisters maybe?????????? Any idea's..........
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post #2 of 6 Old Jul 18th, 2007, 11:03 pm
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Quote:
Originally Posted by Dock
Need some help with a side reflector project......I know I can buy a kit but I like to tinker so I mounted 6 3volt red leds into the reflector and soldered them in a parallel configuration and put 3volts to it and it light up perfect. Now the problem. How do I drop the 12volt on the bike to 3volts......Resisters maybe?????????? Any idea's..........
A 470 ohm resistor will get you very close if your LED's are the standard 20 milliamp variety. 9 volt drop/.02 amps = 450 ohms. 470 is good.

Placed in serious with the LED array of course.


Oh yes, Radio Shack has em - PN 271-1115

HTH

John

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post #3 of 6 Old Jul 19th, 2007, 6:48 am
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Quote:
Originally Posted by bowlesj
A 470 ohm resistor will get you very close if your LED's are the standard 20 milliamp variety. 9 volt drop/.02 amps = 450 ohms. 470 is good.

Placed in serious with the LED array of course.


Oh yes, Radio Shack has em - PN 271-1115

HTH
If you use a single resitor for all 6 LEDs then it should be a 2 watt resistor (9*6*.02)

It would be better to put 6 1/4 watt resistors in. Each LED would get a resistor and then connect all of the resistors (other end) together (parallel) to the 12 volt source. This should give better uniformity in light as well.

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post #4 of 6 Old Jul 19th, 2007, 7:28 am Thread Starter
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thanks for the help....I'll post it when I;m done......
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post #5 of 6 Old Jul 19th, 2007, 1:48 pm
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Quote:
Originally Posted by BMWphreak
If you use a single resitor for all 6 LEDs then it should be a 2 watt resistor (9*6*.02)

It would be better to put 6 1/4 watt resistors in. Each LED would get a resistor and then connect all of the resistors (other end) together (parallel) to the 12 volt source. This should give better uniformity in light as well.
Ah yes, thanks for the correction.



Dock,

a 2 watt resistor will be harder to find so the 1/4 watt recomendation will be easier for that reason also. The part number I gave is a 1/2 watt, forget that one.

I was originally going to suggest a LM317T voltage regulator, but they are trickier to solder up as far as resistor placement if not familiar.

Have fun, you can't hurt anything but the LED's.

John

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post #6 of 6 Old Jul 19th, 2007, 6:51 pm
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LEDs and resistors

Another way is to use one resistor per 3 LEDs--put the 3 LEDs in series with the resistor. Then, connect the two groups of 3 LEDs in parallel. In this case, you would need two 470 ohm, 1/4 watt resistors (one for each group of 3 LEDs). This is per side, of course.

I'm playing with this very configuration (using 9 LEDs per reflector) as an alternative to my current design, which uses two 5-watt resistors. If you route out the back of the reflector, you can recess the resistors so they don't stick up too much.

For help on running the wires, see my installation instructions online--make changes as required because you're not using the 5-watt resistors.

Also, if you need some of those piggy-back connectors, let me know (they're hard to find in some places).

Larry Schumer
Salt Lake City, UT

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