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daznkel · 18th February 2019, 10:33

Typically the forward voltage of the led will be in the range of 2.8-3.6V and the forward current 20-30mA. These values, as already mentioned, vary according to many things, but colour is one of the factors.
So if you assume a 12V supply, from the car. A forward voltage of 3.2V and a forward current of 25mA, you would be looking at a 390 Ohm resistor.

(12V-3.2V)/0.025 Amps=352 Ohms preferred value resistor = 390 Ohm.

To reduce the brightness, assuming you are going to keep the forward voltage the same, the current has to be reduced, by increasing the resistance.

18th February 2019, 10:33	#5
daznkel Posted a thing or two 04 MG ZT+ 190 XPG & 99 (T) Dealer Launch 75 V6 Connie Auto Join Date: Oct 2012 Location: Plymouth Posts: 1,080 Thanks: 615 Thanked 456 Times in 309 Posts	Typically the forward voltage of the led will be in the range of 2.8-3.6V and the forward current 20-30mA. These values, as already mentioned, vary according to many things, but colour is one of the factors. So if you assume a 12V supply, from the car. A forward voltage of 3.2V and a forward current of 25mA, you would be looking at a 390 Ohm resistor. (12V-3.2V)/0.025 Amps=352 Ohms preferred value resistor = 390 Ohm. To reduce the brightness, assuming you are going to keep the forward voltage the same, the current has to be reduced, by increasing the resistance. __________________ Click HERE To Be Added To The South West Members Location Map Upgrades/Mods so far: Custom Angel Eye DRL's, MG7 Rear lights, Custom Door Cards, MGR Plates, Red Alcantara Seats, Black Oak Dash, Powerflex bushes, Plenum Spy Mod, Rear Light Seals, 5000K HID Kit, Navall 3 DD, Blue LED Conversion, Custom badges, Union badges, Flip key. Working on more! [SIGPIC][/SIGPIC]