hoonigann

iTrader: (3)

Hi all. i am trying to change the lights in my head unit to blue leds. i used an analog multimeter to determine the positive and negative sides on the circuit board and i used 820 ohm resistors for every light. but none of them will light up. i thought maybe i installed them backwards so i flipped a few to test the theory and still nothing. Im at a complete lose.

VIP1

820 ohm sounds loo high.
What is the rating of each LED?

Here is an LED Calculator to determine the resistor you need:
http://led.linear1.org/1led.wiz

I entered LED Specs of 3.2V 20ma with a 14V supply (car running voltage) and it recommended 560ohm
If I enter 30ma instead of 20ma, the recommended resistor rating drops to 390ohm.

hoonigann

iTrader: (3)

https://www.superbrightleds.com/more...-mcd/267/1194/
These are the LEDs I am using. I fiddled around with my volt meter with the lights on and connected some of the pins at the bottom of the circuit board and I got the display to light up
Idk if that's helpful

I got 390 ohms on the resister calculator. But when I was messing around connecting pins I got a few of the LEDs to light up

https://www.superbrightleds.com/cat/resistors/
These were the resistors I used
The resistor calculator said I need a 1 watt 390 ohms resistor. Would 1/4 watt work?

VIP1

I don't know what fiddling you did to get the display to light up or get a few LEDs to light up with that high of a resistor, but be careful you don't short out or over-volt something.

Looking at those LEDs, they are 3.5V, 30ma rated. Using the car's supply voltage of 14+V, you should be using around 390ohm resistor. I little higher is OK because it will give some buffer (470 ohm will drop the current to a safer longer-life rating instead of peak rating but a little dimmer so go between 390 - 470 ohm), but the 820 ohm you have is way too high.

hoonigann

iTrader: (3)

Ok cool I'll give that a shot. Thanks a bunch!