guys, looking at selecting resistors for some dash LED's Seems like everyone uses a different number. For this LED (http://www.superbrightleds.com/specs/b2545_specs.htm) I'm using 30mA (not the peak 50) as my current, 12V supply voltage (even though it's a little less) and a 3.5 LED voltage (not 4.0 MAX).

Is there any reason I shouldn't use the 330 Ohm resistor like is calculated here? http://www.superbrightleds.com/led_info.htm

When you guys do this, what viewing angle are you choosing. I'm thinking the 45* would be good?

Thanks,
Andrew

 

I think you meant 330 Ohm, and not 33. At 330, you'll be drawing about 25mA at 12V, or about 32mA at 14V. There's just one problem - note that it is rated for 50mA peak only when being pulsed on and off - on no more than 10% of the time. For continuous duty I wouldn't exceed what is listed in the next section - you'll see that all of the specs are given using only 20mA of current. 30mA continuous would be a 50% overdrive - expect short life. I'd drop back to a 560 ohm - this would give about 19mA with 14V.

I don't know what you're using them for so I can't say much about the viewing angle - except that I've noticed that people doing dash replacements seem to favor the 120* models.

 

Yeah, this would be for the radio, HVAC, headlight control, cargo lamp etc. I guess I should measure the voltage across a current incandesant to see what the actual voltage will be. I didn't notice that test amperage of 20A, so you think going at 30A is playing on the edge?

 

Definitely too high - that's 50% over and would give you a fairly short life out of them. Keep it under 20 - it'll still be plenty bright.

And I hope you meant 30*m*A - 30A would result in a very quick BANG! as it lets the magic smoke out!

 

Cool, 560 it is. Here I come RS.

 

What color are you goin with?...I'm assuming red to match the truck?

 

just buy the led lights with the corresponding resistors...then buy some doubled up and tripled up resisitors if you want to double the bulbs....

 

nahh, going blue. Have always like it and did that for my gauges...I hate to say it but kinda like the VW look.

 

I prefer THIS calculator for my LED's.
Always go on the side of caution with the resistors.
And try to get the 120 degree viewing angle LED's, it will make your job so much easier.