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Suggestions – LED Project

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Greg,
Thanks for the diagram. This looks like the perfect setup for illuminating the reflectors. I have been going through the components (Rebel LED Tri-Star, BuckPuck, and Heat Sink) and the cost is getting a little high. When going back to your previous comments, am I correct in understanding that each Tri-Star includes 3 LEDs and 1 BuckPuck would be necessary for every 2 LEDs? Following with this understanding, you mentioned that cost could be lowered with the replacement of BuckPucks by resistors. What resistor specifications would you suggest and how would they be applied?

Thanks again, Great Ideas.
Ray (64BJ8P1)
 
RAC68 said:
I have been going through the components (Rebel LED Tri-Star, BuckPuck, and Heat Sink) and the cost is getting a little high.
Click to expand...
Yeah, they can get expensive. High powered LEDs are a lot harder to make than standard bulbs. Since most people don't drive their Healeys all that much, a standard bulb can last almost as long as an LED for a fraction of the price.

RAC68 said:
When going back to your previous comments, am I correct in understanding that each Tri-Star includes 3 LEDs and 1 BuckPuck would be necessary for every 2 LEDs?
Click to expand...
Yes and no. Each Tri-star has 3 LEDs but a Buckpuck can light more than two. How many rebels it could light? I'm not sure. The main thing for the puck is the input voltage needs to be greater than the output. So if your voltage is 13.4 with the car running, you could get 6 in series. 2.1vx6=12.6v The reason you'd need 3 pucks at the back is from the way the car is wired. The running lights are one circuit. Each turn signal needs a puck because you are running a higher current than the running lights and each side needs to be separate or you'll get hazard lights. A standard 1157 bulb has two filaments that keep the circuits apart.

RAC68 said:
Following with this understanding, you mentioned that cost could be lowered with the replacement of BuckPucks by resistors. What resistor specifications would you suggest and how would they be applied?
Click to expand...
To do this, you'd need to find the max voltage your car puts out. Hookup a volt meter and run the engine up to maybe 3000 RPM and hold till you get a stable number. Check a couple different lower RPMs too, say 1000 and 2000. The reason you do this is the LED has a voltage range that shouldn't be exceeded. Even the rebel line has different max voltages. The Tri-stars look like they use the LXM2 series so their voltage range is 1.8v-2.8v with 2.1v being the recommended value. See HERE for the datasheets.
The formula: R(in ohms)= (input voltage-LED voltage)/desired current in amps[/font]

So if you wired a Tri-star in series, the LED voltage= 6.3v
Lets say your max regulator voltage is 13.4v and you want the running lights to work @ 350mA. plugging those numbers in you get 13.4v-6.3v= 7.1v/.35A=20ohms

So that resistor would go on the + wire (red) just before the LED (in series). Use the same formula to figure out the resistor for the turn signal but replace the amp value with something like 700mA. Those resistors would go on the white/brown and white/purple wires and attach to the same LED input.
Will those values look good and be bright enough? Dunno, you will probably need to try a couple different resistors to find something you like.

P.S. Forgot to mention, the resistors need to be fairly high wattage. I've gotten away with 10 watts (I think), 20w would be better.
 
20 WATTS !!! WOW!! That is a lot of wasted power isn't it???


-------------Keoke :frown:
 
I tried a 1 watt resistor once "just to see what would happen". It melted the hot glue I had used to mount it in about 10 seconds. Got the glue hot enough to start it smoking. Kinda why I've been leaning towards buckpucks in this thread.
 
Hi All,

I want to thank all who contributed to this thread. Greg, you have given me a better education on LED implementation than any of the web documents I have read on the subject.

Again, to Greg and all others, thank you for your time, ideas, and the knowledge and perspectives you have imparted on this and all other threads. I have really enjoyed and greatly appreciate and value the exchange.

All the best,
Ray (64BJ8P1)
 
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