Got a question about driving LEDs? (Another work in progress)

OK, lots of people ask questions about driving LEDs. So here's a list of common answers and pointers to documentation that is useful.

But not any more...

Thanks to a lot of feedback and valuable assistance by many members, this has achieved a maturity that I think deserves a place in our tutorial section.

This thread remains for any comments you might have, and also because many existing threads refer to it.

Oh, in that case it's brilliant, hehe. (: I was just wondering what else could be added to it. Though if you set out to speak generally on the subject it's golden. Might want to lock the topic.

Here's a calculator for the resistor to be attached in series with an LED

http://home.cogeco.ca/~rpaisley4/LEDcalc.html

Hope it helps !!

No, and for 2 reasons. Firstly, I am under no illusions that my statement is the final word on the topic, and secondly, sticky threads are great bait for spammers.

Thanks, I've added that one.

its agreat material realy helped me alot....thumbs up....

Great work indeed

Hi Steve
Great exposition!
What is the purpose of the capacitors in output of the switch mode current source?
What happens if there is no load, do the capacitors go pop?

Few suggestion on improving the thread:

More info about practical issues such as what power supplies/resistors/capacitors/constant current psu's etc. are widely available rather that just pure maths because if for example you calculate the voltage needed and it's 13 volts then it might be hard for a new comer to figure out which psu to get.

Better explanation of diagrams. Like duke37 asked about the capacitor, I don't really know what it's for either but seen it in many diagrams b4. Also I looked for 0.1uF capacitor and I didn't see anything even close to this value, so more info would be nice.

More info on complex/unusual setups as this is where people have problems most of the time. Like 3x3W led's or 12W led's

Mostly more info and some examples on how to actually wire the led's and constant current circuits especially the ones with unusual requirements, such as the 3 led psu problem (~3x3+4.25=13.25V this is just over usual 12V power supply, is there a way to still use the 12V supply such as by wiring led's in parallel?).

Hope this helps with the brainstorming

Also, this is a useful LM317 calculator, maybe it's worth linking to it from the main post...

http://diyaudioprojects.com/Technica...age-Regulator/

Steve
I think the thread is pretty good as it stands. It is difficult to give one explanation to those of very different abilities. It is often necessary to explain in several ways before the penny drops, when it does, it is very satisfying.
One of the problems is to explain that there are often many ways of doing the same job and compromises can sometimes give more simplicity with almost the same performance.