LED Indicators triple speed

Originally Posted by northwind

Every LED circuit has a resistor in series connected to the cathode.

Sorry, but I'd have to disagree with that. I'm used to buying LEDs individually & soldering them into a circuit. There's loads of places that sell LEDs with wire on the end that doesn't have a resistor in it.

If the LED is rated at 3.3v and you're only supplying it from two AA cells, there's little point in a resistor.

Other than that little factet, we both appear to have the same outcome (note: it's not the 1st formula - the one you quoted - that's right, it's the 2nd)

Edit: Also, since there will be a resistor to drop from 12v to the LED input voltage, you could use both my first & last formulae to work out the parallel resistance required.

[northwind]

Originally Posted by Baph

[Sorry, but I'd have to disagree with that. I'm used to buying LEDs individually & soldering them into a circuit. There's loads of places that sell LEDs with wire on the end that doesn't have a resistor in it.

That's not an LED circuit though, it's just an LED. This is your own link I'm referring to here

I've been writing very badly all the way through this, I just realised... Left out bits I meant to, which probably makes it confused nonsense in places. If I add in about 20 "in a bike application" and "according to the links" it'd work, I think

[mattSV]

Markyboy wrote

what resistors do I need

I wrote

I use 10 watt 10 ohm and they work fine for me

Baph wrote

blah blah technical stuff blah

Northy wrote

blah blah technical stuff blah +1

Maybe I was just lucky

I'm no expert and a lot of people on here know there stuff about electric and I'll pull my head in if if got the wrong end of the stick....

would these not work a 12v resistor

Originally Posted by northwind

If I add in about 20 "in a bike application" and "according to the links" it'd work, I think

I'll agree to that! Although the link I provided was merely an example application of LEDs. You only need a resistor if the supply voltage exceeds the input voltage.

DoubleD, brown blue black gold. That's a 16Ohm resistor. Depends entirely on what you wanted to use it for.

[northwind]

Dunno, they look suspiciously wee though. I think those are intended as series resistors with a stand-alone LED? Could be wrong. But I'd be really surprised if those are going to be able to deal with the job, they want to be 10W or more really I reckon. (rule of thumb, that)

http://www.ultraleds.co.uk/product_i...075c5174cced41

This'd work. Also, be ridiculously expensive

[Viney]

Originally Posted by DoubleD

I'm no expert and a lot of people on here know there stuff about electric and I'll pull my head in if if got the wrong end of the stick....

would these not work a 12v resistor

Is what i have/had, until the indicators backed up that is...darn water

Originally Posted by northwind

Dunno, they look suspiciously wee though. I think those are intended as series resistors with a stand-alone LED? Could be wrong.

http://www.ultraleds.co.uk/product_i...075c5174cced41

This'd work. Also, be ridiculously expensive

I have 2 of those sitting in my tool box at home doing nothing, brand new, I got them when I was going to put LED brake lights on my cage to fool the light check computer. Didn't go ahead with it though.