pushbutton led voltage

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=102350
Printed Date: July 15, 2025 at 8:00 AM

Topic: pushbutton led voltage

Posted By: spaspecker
Subject: pushbutton led voltage
Date Posted: February 19, 2008 at 4:33 PM

I already have pushbutton ignition in my car, but want to replace the button I have with this one:

illuminated pushbutton

as I want the button to light up

My question is how do I wire the LED? I know I can take 12v from pretty much anywhere in the car but the spec on the button says the LED uses 1.85v - so how do I "step down" 12v to 1.85v?

Replies:

Posted By: spaspecker
Date Posted: February 19, 2008 at 4:36 PM

sorry guys, something wrong with the linky - try this link

Posted By: Ween
Date Posted: February 19, 2008 at 10:11 PM

hi,

assume that when the vehicle is running, you'll probably have more than 12 volts available then

lets make it a bit higher than typical (14.4=Vs). forward voltage for the led (1.85=Vled) then subtract

Vled from Vs......14.4 - 1.85 = 12.55 now take this amount and divide by the forward current of the led.

from the spec sheet iled = 50mA max(you'd probably not need to run the led at max current) so lets run it

at 25 mA...... 12.55 / .025 = 502 ohms. so start with a value around there but don't go any lower than

251. less current equals less brightness

hope this helps

mark