Car Alarm Blinking Red LED – Version I

PROBLEM: My new car has an alarm, but no visual deterrent!

SOLUTION: “Install” a blinking red LED similar to those on other alarm systems.

1 – bright red 5mm Blinking LEDs:
1 – bright white 5mm LED:
1 – C cell battery clip: Radio Shack:
1 – 75ohm resistor.
2 – Cannibalized computer switches. One power button, one reset button.

I was originally going to access the wiring under the console / dash, and use a relay switch or similar system for having the light come on when the car is off. Once again I decided to go with the less invasive approach… a battery pack with no wiring / drilling.

Also, I figured “as long as I’m creating a battery powered light, I might as well make it functional as well so I put a second switch and LED on the back of the unit as an emergency flashlight.

While the unit doesn’t look that great in the day, at night the placement of the LED along with the black shrink tubing make it look really good at night.

A few notes: First, the blinking red LED was designed to focus the light into a tight viewing angle. This made the light not so bright / visible from the sides. I grabbed some sandpaper and sanded up the LED to make it diffuse the light which worked GREAT. Second, the LED was too bright with no resistor (it would attract more thiefs than deter them) so I stuck in a 75 ohm resistor to bring the juice down. This will also help the batteries last a bit longer.

Here is the finished unit in the car. This is a “first draft” until I decide how to make it look better in the light.

You can see the LED from the back of the car very well. In fact, it was so bright I had to put in a bigger resistor to “calm it down”.

From outside in the dark it actually looks really good. The placement is excellent.

4 thoughts on “Car Alarm Blinking Red LED – Version I”

  1. Hi ,
    That is awesome
    I will like to create the same, My car was broken into more than once in the last month. Could you please send me the diagram of how to do it? and the components?

    Thanks a lot


  2. I had a couple questions, first why should there be 2 LED’s if only one is being used. It should just be a simple series circuit. and what is the reset button for. I am honestly interested. I would appreciat it if you could send me the schematic or any better explanation.

    Thank you,

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