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adding a LED to an alarm

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=13154
Printed Date: August 27, 2025 at 9:08 AM


Topic: adding a LED to an alarm

Posted By: stuBacker
Subject: adding a LED to an alarm
Date Posted: May 05, 2003 at 12:46 AM

hi, I have already got a flashing led on my dash and wanted to add one to my number plate. I have noticed that the negative side of the flashing led is the one that activates the led and makes it flash as the voltage actuates from 12V to 2V(roughly).

I have already wired in the led on the boot but :

1) I need to drop the voltage down to 2V as it is a 2V led

2) It is now about a third of the brightness.(when I put the negative to an earth on the car it is really bright, however when I put the negative onto the negative of the other flashing led it is really dull.(the positive is to the positive of the other led)) so that when I arm the alarm it starts to flash.




Replies:

Posted By: christophereet1
Date Posted: May 05, 2003 at 4:22 AM
hello,

I will tell you a little about LED'S first before I tell you how to "most likely" fix this problem.

A Light Emitting Diode is really a diode. They have max voltages but brightness is controled by current not voltage. Yes you need so much voltage but very the current and it will no longer be bright. lower the voltage and it will no longer be bright. When you see 12 volt on the meter you really have a resistance that isn't being seen by the meter so measuring voltage is almost pointless.

most commin solution put the led in series. Be careful these are diodes so + to -, + to - otherwise no light will work. Really you can just revierse the pins on the led and it will not do damage

christophereet1@aol.com






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