Newb seeking some help

[Trev]

Well this is my first post, so hi everyone.

I have some very basic knowledge with electronics and LED's.

I'm trying to put together a LED fog light setup for my car. Just like this:

I will be using 20 (10 per side) 10mm, 40*, 380mA, Vf 3V white LED's.

What i need help with is determining what to use for limiting the current.

Any other helpful suggestions are welcome.

TIA

 

[mikey99]

Like many your fog light are probably just for show and are to be always on.

1. Take apart your headlamp and find a point (in your parking lights where you can safely solder two wires to the light terminal (- and +)
2. measure the voltage with a multimeter (should be ~12)
3. Since you got 9 LEDs i suggest

wire 3 LEDs in series (+ to - to + to - to + to -) and a resistor at the negative terminal to balance the current to the group . You now have 1 group.

- Make 3 of them.
Connect the 3 groups in parallel to the wire terminals

To determine which resistor ... use ohms law or
http://led.linear1.org/led.wiz

This way when your parking lights are on, your foglights are on
When you headlamp is on, the parking lights remain on.

If you got foglights prewired, no need to do step 1, just use these, make sure to measure the voltage and use the correct resistor,

Also, your 380 mA LED's will likley want some good soldering and heat shrinking to protect them from road vibrations.

All the best, and dont blow a fuse.

...P.S you can also connect all of them in parallel but you will be using many more resistors and also your current demand will be pushing 4 amps (per foglight)..
P.SS... you can connect the other foglight the same to one headlamp (if your fuse capacity is not exceeded by the amount of current required... i suggest going the extra step of connecting the other foglight to a separate head lamp)

 

[Oznog]

Are those the 1W packaged LEDs? I have some of those!

That plastic-cased LED style is woefully short of ways to dissipate heat. 1W is really beyond "pushing" the technology. Since the ONLY way it has to dissipate heat is through the leads, the key is short leads and a copper PCB or I guess heavy gauge wire right behind it to spread out the heat. Even still, there may be reliability/efficiency issues at 1W. The thing is, that bezel seems to require the leads be long. But, oh well, it's not like you need it to drive.

Check your resistor wattage. This will likely exceed the wattage of the common 1/4W resistors.

 

[Trev]

Yes they are 1w LED's. I'm not to worried about reliability, bought them off of eBay for cheap. This is just a little side project im working on. If all goes well i will be going with better LED's.

The main thing i am worried about is the inconsistency in a vehicles electrical system. Power can range from 10v to 22+v. I need something that will keep the current constant...

 

[Gunner12]

You might want to search for a buck or boost driver that can handle sudden changes in voltage.

:welcome: