Electrical Noob, need help with LEDs

That's what they are saying. Good luck.

thanx, i'll try that some time soon, thanx for all your help and oxy, you are quite knowledgible when it comes to electric stuff 8)

If you're not going to use resistors then do the following.

With 1.7 volt LEDS, the ideal number of LEDs will be 14.4V/1.7V = 8.47 LEDs. Round up and use 9 LEDs in series. They won't be as bright as they could be, but at least you won't blow anything.

With 3.6 volt LEDS, the ideal number of LEDs will be 14.4V/3.6V = 4 LEDs. These ones will likely give you maximum brightness without burning them out.

This stuff is actually pretty simple. I'm working on some variable intensity headlights right now.

so you mean 4 or 9 per string and do asmany strings as i want

I think Oxy and 03rolla are in a higher class than me when it comes to this stuff. I have been tought all the thoery and whatnot, but only aply it to AC cuircuits. Everything I know about DC is just form aplying the principles I learned, and a lot of trial and error.

I may be wrong on the led thing, but I know in my case I have done it and it worked. I just dont want to be held responsible if there is a problem.

Good luck, and hope it works out good for you.

well if youre gonna do stuff out of the ordinary, then you have to take a risk

Yup. You can wire as many strings as you like in parallel. LEDs don't use much power. The maximum number of strings you could parallel would be about 1750 before your alternator would have trouble keeping up.

cool see i can never figure out max numbers like that but your analogy of how to calculate how man per string seems fairly simple

Well now you know how many LEDs to wire in series depending on which LED you end up choosing. Go do it and let us know how it works.

you know, its really hard to tell for sure since its only typed letters, but.........

OXY are you being sarcastic?

No, I'm not. It's just hard to explain it to people who don't know the theory when it has become so intuitive to me. For me it's like trying to explain why 1+1=2.

Oxymoron, I bow humbly at your knowlege. I just found this formula, dug out what I used to build my flag display. I built the dropping resistor into my power supply, that is why I didn't see it looking at the display!

R (resistance to use in a series LED circuit) = V (source voltage) - [N (number of LEDs in series) X Vled (voltage rating of LEDs used)], divided by Iled (current rating of LEDs used).

Assume (10) 1.2V 20ma LEDs in series:

So, R=14.4-10X1.2, divided by .02

Or, R=2.4/.02

R=120 Ohms.

You are 100% correct, to wire 10 LEDs in series with a 14.4V source, you DO need a 120 Ohm resistor in series with them! The value drops to 80 Ohms at 13.6V (car not running), but to keep the LEDs from a early death, I'd go with the 120 Ohm.