# led bus bar?



## dawizzard (Oct 16, 2007)

hi there.. thx in advance to anyone who can point me in the right direction..

i am building a light system for a 12 volt powered system...

i want to join in parallel 6 led lights to be mounted on an aluminum surface... 6 holes will be drilled through the aluminum and on the other side i want to solder the + all together and all the - together on a bus bar ...
this bus bar will be connected at the end with the power supply wires ... the room i have on the other side of the aluminum plate is only about 1/4 inch clearence so the smaller the better

this will be packed with silicon or other water proofing material... 

my question is .. what site can i purchase the bus bar... better yet .. what kind of bus bar can i use

i want one side of the bus to be + and the other -
and also be very very small.. i dont want to use cut and splice of wire method.. i would like to have it a clean connection... 

anyone with any advice will be greatly appreciated... thx again...


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## Lightingguy321 (Oct 16, 2007)

Bus bar and Circuitry aside, what kind of LEDs are you planning on mounting? If they are Luxeon, Cree, SSC, or anything similar (as in high output that has a heat sink slug on the bottom), do you plan on having a heatsink region on the bus bar? If not, please reconsider because any high output LED should be heatsinked other wise the LEDs will probably die a lot faster. Do you know what current you will be running these at?


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## tonycollinet (Oct 16, 2007)

Another thing to bear in mind - LED's in parallel will not share current very well, so some will likely be brighter than others.


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## IMSabbel (Oct 16, 2007)

tonycollinet said:


> Another thing to bear in mind - LED's in parallel will not share current very well, so some will likely be brighter than others.



And in the worst case, the brighter ones can get hotter, and thus drop in resitance, and get even brighter...


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## dawizzard (Oct 16, 2007)

[FONT=&quot]Yellow 1900mcd T-1-3/4 5mm LED 
[/FONT][FONT=&quot]LED Holder[/FONT]
[FONT=&quot]radio shack link

this is the name of the LED online... hope this answers the kind of LED

hmm never thought of a heat sink.. didnt know i need one.. 
ok.. ill repost my question...lolol..

the lights are for extra turn signals mounted outside on a motorcycle
http://i184.photobucket.com/albums/x98/dawizzard70/rearpic.jpg






if this link works.. u will see where i want to mount them in red...

if anyone has any ideas on LED's and other parts i will need.. plz.. post them.. 
im mechanically inclined not electrically...LOLOL 
i can solder and stuff... and put things together... just need the parts .. what to order and maybe where to order
as you see in the pic.. there is about 1/4 of an inch clearance... so anything i put in there has to be small and water tight.. so i was thinking of siliconing the area after i was done installing the lights... 

thx for all and any help....

[/FONT]


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## tonycollinet (Oct 17, 2007)

OK

Those leds can definately not be wired directly in paralell. You notice the voltage rating is 2.1 typical - 3V max, and they'll have a very steep V/I curve. The led with the lowest voltage will take all the current (and probably burn out) the rest wont get any.

Each LED will need a separate series resistor, assuming you don't mind wasting a bit of power - and on a bike that should not be a problem. You can then wire each LED/Resistor pair to your busbar. Why not use stripboard. This will allow you to connect your led to your resistor, and you could solder on a couple of solid wires, to act as a busbar.

Don't know what your electrics voltage is. We'll try 6V and 12V. Max current is 40mA, so we'll choose 30ma to give a bit of headroom.

Assume the LED voltage is 2V

With a 6V supply - that means you want to drop 4V in the resistor at 30mA - R=V/I = 4/0.03 = 133.3 - you can get 133 or 130 ohm which will do the job. Power in the reistor will be 4*.03 = 0.12W = 120mW, so you can use basic 1/4W reistors.

With a 12V supply, you want to drop 10V in the resistor at 30mA. R=10/0.03 = 333.3ohm - you can use 330. In this case power will be around 10*.03 = 300mW, so you will need to get 1/2W resistors.

EDIT: Just re-read your post. You have 12V, and want 6 LED's. Best way to do this is to have 2 strings of 3 LEDS in series. Each string then needs ONE resistor to control the current. Each string of LEDS will be around 6V, so the resistor will need to drop 6V at 30mA

6/0.03 = 200ohm. Power is 6*.03 = 180mW, so you can get away with 1/4W again.


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## dawizzard (Oct 17, 2007)

tonycollinet said:


> OK
> 
> Those leds can definately not be wired directly in paralell. You notice the voltage rating is 2.1 typical - 3V max, and they'll have a very steep V/I curve. The led with the lowest voltage will take all the current (and probably burn out) the rest wont get any.
> 
> ...



i will hook them up like this correct??




thx for the information Tony.. 
thank you so much...
when i get the parts and it installed correctly... correctly is the KEY word there...LOL ill post a pic for ya...


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## tonycollinet (Oct 17, 2007)

Close - but in that picture you don't get 3V in accross each LED as stated in the picture. The led voltage is determined by the LED (in your case, 2V (typical) per led). The remaining voltage (12-8 = 4V) is accross the resistor. Then you choose the resistor value to get the current you want.


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