Custom LED tail light help

[Sirius815]

I think it may be cheaper/easier to get a regulator used for LED flashlights from the website I posted earlier. Also if you do this, you will not need the 120ohm resistors.

Usually, for LEDs you'll want a current regulator which is more difficult to design than a voltage regulator, but a voltage regulator should also work. And since you have all the tech data, you can design your own perfectly.

A voltage regulator is actually really easy if you use a LM317 btw. The output is very stable (will get rid of the voltage ripple the buell's have at idle). http://www.national.com/mpf/LM/LM317.html#Overview

 

[Loki]

So if i use the resistors and build the LM317 circuit i would be fine still? I see the circuit has a variable resistor, would i have to set it up to get it to work right? I dont want to blow something again.
Or if you can point at which current regulator on the deals extreme would work for the 12v (I still cant find the current the buell puts out and my multimeter doesnt measure current very well) And if use the current regulator i would be able to forget all the resistors correct? I would just need to buy a current regulator for all for parts. (turn sig, brake, running)

 

[Sirius815]

I looked through dealextreme again and now am leaning towards a LM317 setup as my recommendation to you. If you give a link to the specs of the LEDs you'll be using, I can build up a circuit on Multisim for you.

EDIT: The buell doesn't put out current per say - it has a voltage and is capable of putting out lots of current (like when you need to start it). Remember current is based off of voltage and the load (resistance). The LEDs will draw minimum current and the power usage of the LM317 is minimal.

 

[Loki]

http://www.amazon.com/gp/product/B003SK7WW8
The leds im using.

Thanks for all the help Sirius. Whats your story on electronics knowledge?

 

[Sirius815]

Um...3 semesters in High School - 5 semesters in College - and 7 months of Army training

 

[Loki]

Hmm, i got the highschool college and army combo as well. But not as much yet

 

[Sirius815]

What's your MOS?

 

[Sirius815]

Okay - Multisim is giving a few slight issues - but such is the electronics world.

Here's the LM317 you need: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=LM317TNS-ND

Also look at the data sheet: http://cache.national.com/ds/LM/LM117.pdf

On the first page is the typical applications diagram. The two capacitors are not required, but could definitely help out with the varying voltage at idle and when riding. I would also try to get the 5k potentiometers here, along with the 240ohm resistors. If you buy all the ones you need, then you'll save on shipping costs later. Also - you only need one regulator for the blinkers, as long as you run the wires to each blinker from the regulator.

When you first build it and start to adjust the potentiometer, leave the LEDs disconnected first and measure the voltage output of the regulator (on the bike). Then adjust the potentiometer as needed (I got somewhere around 70% from max for ~9v). Also test the current output with your multimeter when you connect the LEDs to it to (put the multimeter in series to measure current) ensure you are not overdriving the LEDs (remember 20mA per parallel branch). Check the voltage output after that to ensure voltage is still being regulated. The array of 3x10 LEDs will only draw ~200mA of current, however I recommend to still screw a small piece of aluminum to the case of the LM317. The LM317 is capable of up to 1.5A of output, so in terms of LEDs, you can connect a lot of them with out having to worry about the chip (or use higher power LEDs). Just ensure you have a heatsink with increased current.

Oh - use an LED flasher relay of course

 

[Loki]

So I can build 3 regulators and since the one for the turn signals is never both on at the same time, i can run it to both signals?
I dont need the 120 resistors on each series of LEDs, just the ones on the regulator?
And i forgot which led flasher relay it was. EPnumbersomething. And i asked autozone if they had some and they said NO WE DO NOT CARRY LED FLASHERS!
Thanks for the help again. My MOS is 91k (armament repair) and i liked it but im having to change cause the army is always screwing you for no damn reason. What about you?

 

[Sirius815]

Correct on the resistors and the number of regulators. I am unfamiliar with the part number for the flasher relay.


I was a 15Y (Apache Aramament/Avionics) but now I'm a 12P (Prime Power).

 

[CowboyKS]

Can you see it from outer space? [up]

 

[Loki]

I hope!

 

[Loki]

Ok i got the supplies to make this schematic

But instead of the LM117 i have the LM317 that we talked about.
270ohm resistors since they didnt have 240 (always go higher from what i remember) And the 5k potentiometer is huge! Is that because its a audio-taper? So big, and i have to have 3 of these?!

My question is can i make the circuit above and still be fine, or do i have to find another circuit to make? Thank you.

 

[Sirius815]

The circuit above is what I have built myself and works very well (but I wasn't powering LEDs).

There are MUCH smaller pots that you can get. That's why I suggested digikey (or you can try mouser). Radio Shack is more expensive and have less of a selection.

But it can't hurt to do some trial and error with what you have now. Sure in the end you might have spent as much as the xblight, however at least you learned something [up]

 

[Loki]

Lol i will build a circuit with the huge pot and then later use smaller ones. Theres no way i can fit 3 pots this size in the housing. But even buying from the moneyshack i will still not even pass over 100. Hardly 50, and ive bought my LEDs from amazon so i can get them faster as well which cost about 20$ for 100 (shipping included).

Also we have voltage in and of course voltage out in the circuit but what exactly is the bottom wire out for? Sorry so many questions, but thank you tons for helping me. I love little projects like this.

 

[BuellerPilot]

Didn't read through all this yet but....

Use the pots, determine how you like the brightness. Measure the resistance of the pots and replace the pots with resistors the same value as you had the pots set too. No need to stuff those big things anywhere.

~Mike....

 

[Loki]

Great idea buellerpilot!

 

[Loki]

Wont let edit. But i got the circuit working And have it tuned to output 3.2v (for the leds) but when i try to take my resistance measurement with my multimeter and no matter the range, i get one. I have never been able to take ohm readings and it would be super helpful. What do i do?
I have the craftsman 82141 digital multimeter. Thank you. I was surprised the circuit worked first had go!

 

[Sirius815]

You have to take the potentiometer back out of the circuit and then test it. (or take out at least one leg).

BTW - the third connection on the LM317 is for a feedback. The LM will put out a voltage and senses it back on the ADJ input. Based on the voltage seen here (which depends on the setting of the pot) will determine the new voltage output. It's for a feedback loop.

I agree about replacing the pot with resistors after getting the brightness.

Also remember that the brighter the LED, the shorter its life. Not saying it will blow tomorrow, but it might be a year sooner

 

[Loki]

So i cant measure the pots resistance with it on the circuit? And im still confused on how to do that.

Your BTW kinda confused me and worried me Sirius lol. Dont do that! Youre making me think i did something wrong!

Here are some picture of the circuit and the pot.

A semi step by step on how to measure the ohms would be amazing. I am already really grateful for the help thus far!