LED license plate light
01-21-2009, 09:51 AM
#1
TECH Addict
Thread Starter
iTrader: (3)
Join Date: Jan 2003
Location: Houston/College Station, TX
Posts: 2,584
Likes: 0
Received 0 Likes
on
0 Posts
LED license plate light i made one a few years ago but but i don't remember how i did it and i can't seem to find the site that had the instructions. it had a spreadsheet that used how many LED's you had and calculated what resistors you needed. anyone have any ideas?
if not, some instructions on how to make one of these would be greatly appreciated!
This is what i found with a search... does it matter how many LED's you use with the two 47 ohm resistors it specifies in the diagram? i wouldn't think so since LED's pull so little amperage... any ideas?
if not, some instructions on how to make one of these would be greatly appreciated!
This is what i found with a search... does it matter how many LED's you use with the two 47 ohm resistors it specifies in the diagram? i wouldn't think so since LED's pull so little amperage... any ideas?
Last edited by Onyx Z; 01-21-2009 at 10:18 AM.
01-21-2009, 11:27 AM
#2
TECH Regular
Join Date: Nov 2002
Location: Augusta Ks.
Posts: 418
Likes: 0
Received 0 Likes
on
0 Posts
It all depends on what the leds pull for current then how many in each leg because a led is a diode and diodes drop more or less .7 volt.So this will give you the voltage drop for the leds and you mutiply the number of legs to get the current total.Take the voltage drop for one leg and subtract it from the supply (12v) and this will give votage drop needed across the resistor.Now using ohms law E/I = R you have the value for the resistor and then use ExI^2 to get the wattage of the resistor then so you don't fry it get one 2x and this should get you there.