??? to the LED guys here???

I know LEDs usually need resistors on them, or at least in the circuit to prevent too high of voltage. would it be safe to assume that if on a curcuit board, incandescent bulbs are replaced by LEDs (component not PLCC or such), that resistors would be needed. this is NOT on a tacoma let alone a toyota. only info i could find for this vehicle was a completely custom setup instead of using factory locations for bulbs. essentially this vehicle uses what looks like the mini twist sockets in our fog light switch and A/C panel (2005+), but they are soldered to the surface of the PCB where the lead of the bulb wraps around the socket. using or not using the socket looks like would make no difference


Im not asking you guys how to do what i want to do. i already know how to do it. just would like to know bout the resistors

oh and no i do not have multimeter to test. found my old one stuffed away with batteries all corroded.

Thanks

 

yes you will need resistors. Heres how to figure it out. First in the specs of the LED you will see Vf (forward voltage) and IF (forward current).

Example PLCC2 White LED. Vf = 3.2V IF = 20mA

First you need to know how much voltage to drop across the resistor.
V = Voltage at the bulb 12-14V for a car.

V - Vf = drop across resistor.

14V - 3.2V = 10.8V (the voltage needed to drop across the resistor)

Now you need the resistance of the resistor needed to drop that voltage at 20mA (the rating of the LED)

R = E (V) / I (If of the led)

R = 10.8V / 0.020A (mA converted to A) = 540 Ohms

You will need a 540Ohm resistor to get 20mA on the LED at max voltage of 14V.

Now you need to know what power rating resistor you need.

P = E (voltage across resistor) x I (Current through resistor)

P = 10.8V x 0.020A = .216W or 216mW you will need a 1/4 (.250)W resistor.

Now If you want to put 2 LEDs in series. just add two Vfs together and use that value as Vf in the first equation.

3.2V + 3.2V = 6.4V Now use 6.4V as the Vf in the first equation.

Note: always use the high end of your voltage range for this calculation. If you use the low end then at higher voltage you will overcurrent the LED.

 

Holy shit.

 

x2

 

JEEEEEEZUS CHRIIIIIIIIIIIIIIIST

 

I kinda said the same thing...

EDIT: Oh he's an electronics engineer.

 

and that tw, is why I do what I do, I just wasn't that good at physics.

 

^^Dude I love your name.

 

thank you, it's actually in honour of a buddy of mine over in Iraq, that's what he used to call me. Even when he gets back, I don't think I'm gonna change it.

 

wow. umm....question answered. thanks that was what i was looking to find out

 

Project complete

Fruits of my labor. "pink" LED cluster illumination in 2006 Cobalt SS (the GF's, not mine)



dont mind the date on the pic. camera is an 'antique', stays dead more than not.

Thank you prerunnerseth. problem free job

 

basic electronics guys

....prerunnerseth your a showoff!!

 

rrriiiiiight.....

 

What's that supposed to mean?

I have pink needles and some idiot lights are pink in my truck.

 

1 - here, here and here
2 - of course (for the cluster only)
3 - ? couldnt help you there....but i know i have had a guy from vegas and SC mail their clusters to me and i did them. prerunnerseth also does a mail service for gauges as well.

remember, you cannot change the climate controls area, those have to stay orange per the sandwiched plastic.

 

scouts honor this was actually not pain to do, except for removing the painted color filter crap on back of the face. (compared to my damn HU LED swap)

now for something to ponder....installed LED dome light (in the cobalt), now when in "door" position with door closed it still emits very dim light. swapped with bulb in my truck, same deal????

 

This means you have some current leakage. Normally not enough to light a bulb. but, with leds its just enough to make it light up a little. My wifes car is the same with with the two map lights for the rear. only way to solve this would be to redesign the circuit with relay.