32 vdc led circuit design ?

[Sparkie101]

Hi All
Am hoping someone can help me figure out a good and simple way to create a 6 (white) led circuit to work on a 32vdc supply. Might build 10 of them.
Any ideas?
Thanks for any help

 

[Reloadron]

There are several ways to go about it, however, you aren't giving much information. Have any LEDs in mind? I mean 6 white LEDs doesn't say much as we are missing the LED specifications. All white LEDs are not created equal, things like forward voltage and forward current are pretty important specifications to make suggestions for you.

Ron

 

[Sparkie101]

Hi Ron Thanks for your interest. I dont have any experience with leds so I dont have much info to give.
The app is to replace existing 32vdc bulbs on a boat. So am hoping you can suggest type of led etc. Also it can be more or less than 6 leds.
J

 

[Diver300]

**broken link removed** is a reasonable calculator for working out the values and arrangements.

It's shortcomings are that it will design around too many LEDs for the supply voltage, leaving a very small voltage drop across the limiting resistors.

Also, if more than one string of LEDs are needed, it doesn't even them up. For instance on 32 V, with 3 V LEDs, and you want 16 of them, it will put 10 in one string and 6 in another. In the string of 10 LEDs, there is 2 V across the resistor. That is a very small proportion of the 32V, and if the supply drops to 31 V, the LED current halves.

You would be better to use two strings of 8 LEDs, leaving 8 V across the resistor.

 

[MikeMl]

Note that if you are planning on using the high-output LEDs (0.3W on up), they must be mounted on a metallic heat sink to get rid of the heat that they produce. Also, they are more finicky about current regulation and should be driven with a constant-current regulator (not with a resistor). Look around on**broken link removed**.