Comments on: Blinking Red LED Car Alarm Light

By: Rob

Rob — Sat, 13 Feb 2010 22:25:59 +0000

Ray, your solution sounds exactly like my earlier solution here: http://www.nifty-stuff.com/car-alarm-1.php

The problem with that / your solution is that you have to manually turn the light on and off every time you get in / out of your car. I got tired of doing that after about 10 days.

So far, the re-implementation of my idea first discussed in this post is working great, and I think my total cost was only about $1.50

By: Ray

Ray — Wed, 10 Feb 2010 00:56:11 +0000

I can’t believe that you guys are still fooling around with a 12v solution to the flashing light problem.
after a while I think (actually I know) it gets to be an ego thing. My solution, see 5 Feb above, all over in 10 minutes. Maybe better from the car battery, but life is too short.

By: Rob

Rob — Tue, 09 Feb 2010 23:29:38 +0000

Well, yesterday I visited a well respected car audio / alarm company in the area and talked to 2 guys that have been doing installs a LONG time (13 and 25 years). Both of them said they would wire this light exactly the way I originally did and they actually would NOT use a relay (but they gave me a few free ones to play with anyway… SCORE!).

I told them about my battery problems and they said it was almost guaranteed to be a coincidence. Honestly, the more I think about this, the more I tend to agree with them. My car battery was already about 6 years old and I believe was already having problems independent of this circuit.

So, in the interest of experimentation and taking one for the team I’ve hooked the circuit back up as originally designed. I’ll keep you posed and let you know if it works… or my wife will let you know if my car blows up.

By: Rob

Rob — Sat, 06 Feb 2010 23:28:56 +0000

I’m going to grab some relays and play around a bit. I like David’s approach above with wiring to a 12v. relay and I think it is a good idea. My only question is this: Where is the best place to find a ground in my fuse box? I looked all over and couldn’t find anything accessible to ground to.

I’m pretty inexperienced with relays, so when David said, “run ground to prong 96 and 30″ above I’m guessing he actually meant 86 and not 96, right?

By: Ray

Ray — Fri, 05 Feb 2010 23:14:53 +0000

After months of playing around with a connection from the car accessory outlet (blowing the fuse in the meantime) I finally gave up with that idea. I went to a local surpluss store and bought a holder for 2- C type batteries at $0.75, the batteries were two for a dollar from Dollarmar. I then hooked up one of the flashing blue lights that I bought on Ebay $2.50. Total cost $4.25, time to connect 10 minutes, no wiring diagrams. This was at the beginning of October and the lights are still flashing. I put the batteries in the sunglass holder above the windshield with the bulb hanging down where it is quite visible. Some times I turn it off for daylight mostly I do not. These batteries could last a year or so, at which time I will buy another pair. Thank you Darren for the idea I changed it a little bit.

By: Jeff

Jeff — Fri, 05 Feb 2010 22:33:06 +0000

A friend of mine wanted a flashing LED for his car and just hooked up a low voltage 5mm flashing red LED to a 9V battery. Drained the 9V in about 5 days or so, which is sort of expected since the LED consumed about 20mA at 3V or so (using resistor) and the 9V battery provided about 5000mAh.

I copied this circuit and put it on a custom PCB for him
http://www.allaboutcircuits.com/vol_6/chpt_8/5.html

Runs on 2xAA batteries and can use any LED. Using the TLC555 series of 555 timer ICs which is very low power and apparently according to that site should last for months so we’ll see how it goes.

By: Darren

Darren — Mon, 04 Jan 2010 03:48:08 +0000

Hi guys. Just wandered into this thread and thought i’d share a little relevant story re: led power drain.

About 15 years ago, i installed a small dummy security camera outside my mothers house. It had a small flashing led powered by the small squareish 9v battery with the poles beside each other that used to be very common. Think it might have been called a pp3 irc. Anyway, that little led finally quit flashing about 3 years ago…..Thats 12 years flashing on that one little battery !!!

Best example of the miniscule power consumption of one led that i can think off anyway.

By: roy

roy — Wed, 28 Oct 2009 18:44:43 +0000

go to the12volt.com they have all kinds of hookup diagrams. let me know what you think about the site, this should help you wire just about any kind of auto circuit

By: Dan

Dan — Thu, 22 Oct 2009 02:31:40 +0000

The blue LED can take a little higher voltage but no more than 3.5 volts. Another good idea is to use a +5 Voltage regulator using 78L05 or 7805 IC to drop the 12V to a 5 volt. A simple circuit can be built from this website: http://stuff.nekhbet.ro/2006/06/18/how-to-build-a-5v-regulator-using-78l05-7805.html the input voltage range can be from 7V and 20V and the output voltage is between 4.75V – 5.25V. It’s a very simple circuit to build, just add a small heat sink to the IC. On thing that you have to remember, a car battery has a higher Amp than a standard battery which it’s probably causing your LED lights to fail. I’m in the process of building another one myself this weekend using a different design and if I’m successful then I will not only post it here but also have a simple schematic available for free if anyone wants it.

By: Ray

Ray — Wed, 21 Oct 2009 22:37:34 +0000

I forgot to say that I am using a BLUE flshing light which may have a different rating. Any comments,Thanks