# Very simple Led circuit that is making my head hurt....... Help would be great!

#### FluxIndustries

Jan 25, 2012
4
Hey guys my name is Jeremy and I am new to your forum, This is my first circuit and I'm hoping someone will help me with this design. I am not educated in electronics what so ever, but I am learning pretty well as I go. I have been reading, digging, reading more...trying to figure this out myself. At this point I feel there are to many variables for me to feel comfortable with the circuits I come up with.

What I really need is for someone with the knowledge to design a working system (wiring diagram) for me to reference. Calculate the correct regulator and resistor values so I can make sure I'm not shortening the life of Leds, I feel like it's a lot to ask of someone, though at this point I'm at a loss and just need a little help.

I have 3 or 4 high powered Led's that I am trying to make a small auxiliary light out of. The light will be switched and wired into a car so it's a 12v DC system.

I know the circuit will have to be regulated to eliminate spikes from the alternator, I'm pretty sure it would be best to wire them in parallel. These are the specs on the Led's if I am missing something just say the word and I will fill in the blanks.

Continuous Forward Current 750 mA
Forward Voltage 3.6 V
LED Brand Vollong
LED Package 14.5mmx7.5mm
Maximum Forward Voltage 4V
Operating Temperature -35~+50°C
Peak Forward Current 1000 mA
Power Dissapation 3 mW
Reverse Current 10µA
Reverse Voltage 5V
Viewing Angle 120°
Wattage Consumption 3W

I was told the best (easy) way to do this would be with a 12v to 3.6v regulator wired straight to the Led's in parallel with no resistor . True? If so I can't seem to find the regulator I need, they all seem to have to high an amperage rating, then again I don't know whats required to calculate the proper amperage values?

Thank you for looking guys. This small project has given me a great deal of respect for complexity's of electronics.
My brain is killing me! lol

Jeremy

Last edited:

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510

I suspect an appropriate constant current source is the best solution.

Beware placing LEDs in parallel without individual resistors. also beware voltage sources for driving LEDS (without resistors).

#### FluxIndustries

Jan 25, 2012
4
Thank you Steve! This is helping clear some things up.

#### FluxIndustries

Jan 25, 2012
4
With some further research I think I have things figured out. I am having a problem sourcing a 3.6v 3a linear regulator with a 12v to 16v input. Everywhere I look (digikey, mouser,etc) has huge minimum order requirements being it's not an in stock part . Would anyone know a good way or place to find this regulator?

Thank you

Jeremy

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
OK, why do you want 3.6V 3A, and why linear?

It sounds like you're wanting to place the LEDs in parallel (series would be better) and it also sounds like you're looking for a voltage regulator which (as I've said) is a really bad thing.

Here is a constant current source probably suitable for driving 1 of your LEDs

There are other ways of doing it, but this is the quickest and easiest for me to find

#### FluxIndustries

Jan 25, 2012
4
Thank you Steve!
if you could see my jaw hit the floor when I opened that link.... priceless!

I guess I just get mixed up in all the different ways to wire this thing, everyone you talk to or new article you read has "the right way". lol

Thanks again Steve

Replies
2
Views
1K
Replies
3
Views
1K
Replies
1
Views
1K
Replies
10
Views
2K
Replies
2
Views
838