1w, 3w, 5w led resistor

[gizmo13]

Hey all,

I am thinking about making a chaser light project using either 1, 3, or a
5w led (luxeon or star or whatever they are referred to).
I went to ledcalc.com and put in the values I would need and it said that
I would need 5w and 8w resistors.
Isn't there some kind of power resistor or something that I could use. I was
figuring on using a standard carbon type resistor but I don't think that would
work. Would it??????
Help
forgot to mention that it would run off of 12v (for automotive use)

 

[audioguru]

A 5W or 8W resistor is a big wire-wound one. It is big so it can dissipate its heat to the air near it. But modern high current LED circuits do not use a big resistor to limit the current, instead they use a small cool Pulse-Width-Modulation circuit.

 

[Leftyretro]

Here is an example of a 3 watt LED driver module. It generates a regulated 700ma of current from any supply voltage from 6-24 volts. Much more accurate and efficient then using a big hot power resistor. There is a enable signal available so that one can dim the bulb using PWM digital signal if wanted, otherwise it can be used to turn on and off the current.

**broken link removed**

Lefty

 

[Hero999]

Use three 1W LEDs in series rather than a single 3W LED, it'll be much more efficient, assuming 3.5V per LED the resistor will only need to dissipate 1W.

It depends how stable the power supply is. If you're running it from a car then you'll need a current regulator and have to put up with the LEDs going dim with the the battery voltage drops below about 11V (i.e. when the engine is started). If it's being run from a stable regulated power supply then a resistor is fine.