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#302758 - 02/10/2007 16:41 Wiring an LED (in car)
Phil.
pooh-bah

Registered: 14/01/2002
Posts: 2481
So I can't afford a car alarm. Besides, even if I could they're worthless and people round here just ignore them. What I can afford is a flashing blue LED in a nice little bezel. My question - can I connect its - + wires to wires in the car headunit loom (ISO) so that the LED turns on when I turn off the ignition? If so, which wires?

Thank you

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#302759 - 02/10/2007 16:55 Re: Wiring an LED (in car) [Re: Phil.]
wfaulk
carpal tunnel

Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
IANAEE, but I'd use a normally-closed relay. My terminology is bad, so I'll describe each connector. Tie the ignition line of the car to the lead of the relay that activates the switch. Tie the LED in series with the lead of the relay that is turned on and off by the relay and the always-on power from the car. Tie ground to ground.

When your car is on, the ignition line is on, so the relay is activated, which means that the circuit is open (that is, the switch is off). When the car is off, the relay goes back to its rest state, which is closed, which means the switch is on and power flows through the LED.
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Bitt Faulk

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#302760 - 02/10/2007 17:00 Re: Wiring an LED (in car) [Re: Phil.]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31313
Loc: Seattle, WA
Do not do this.

The first time I had a CD player ripped off out of my car, I had installed a blinking red LED on the dashboard to make it look like an aftermarket alarm. The theives ignored it.

Well, I don't know if they ignored it. I think it helped them make the decision of how to get into my car. Instead of breaking a window, they used a crowbar to pry into its hatchback, causing even more damage than a broken window would have caused. I guess they assumed that it was an aftermarket alarm and that I wouldn't have gone to the extra trouble of wiring a switch to the hatch back.

How else to prevent theft? Well, do you own an empeg? (If not, why are you on this BBS?) How about pulling it out of the car and taking it with you? I do this every time. I even cover up the hole so it also *looks* like there's nothing to steal (in addition to there actually *being* nothing to steal).

If you are dead-set on using a blinking LED, you can't plug it straight into your car's 12v wiring system all by itself, you need the proper resistor. LEDs will be burned out by the full 12 volts, but a resistor will take care of it. I forget the value, perhaps someone here can calculate the proper value for you. I seem to recall I installed a hidden switch that would turn the thing on and off for me rather than doing anything fancy to make it turn on when I had the ignition turn off. If you wanted to make it turn on when the ignition turned off, a simple relay circuit wired to the ignition wire would work.

But don't do that.
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Tony Fabris

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#302761 - 02/10/2007 17:00 Re: Wiring an LED (in car) [Re: wfaulk]
Phil.
pooh-bah

Registered: 14/01/2002
Posts: 2481
Ah I never considered using a relay! Thanks Bitt.

Edit: IANAEE? - is that 'I am not an electrical engineer'? If it is I have NO idea where I got that from


Edited by Phil. (02/10/2007 17:02)

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#302762 - 02/10/2007 17:07 Re: Wiring an LED (in car) [Re: tfabris]
Phil.
pooh-bah

Registered: 14/01/2002
Posts: 2481
Point taken on board Tony. Thanks for the input. I'm carefully reconsidering now! I *used* to have an empeg. Well technically I still do. I sold it (provisionally) but couldn't fix an intermittent fault and forgot all about it until recently. That reminds me, I'll need to contact my buyer at the time

As for the resister, yes it has one built in so it can take 9-12v directly.

Thanks for the input.


Edited by Phil. (02/10/2007 17:07)

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#302763 - 02/10/2007 17:20 Re: Wiring an LED (in car) [Re: Phil.]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31313
Loc: Seattle, WA
For what it's worth, I also have had a removable-faceplate CD player stolen from my car. In fact, it was the insurance money from that theft that paid for my first empeg MK1. So those don't work either.

Threads like this serve to remind me just how painful it was to get ripped off (twice), thus encouraging me to continue my practice of taking the empeg with me every single time.
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Tony Fabris

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#302764 - 02/10/2007 17:52 Re: Wiring an LED (in car) [Re: Phil.]
Cris
pooh-bah

Registered: 06/02/2002
Posts: 1896
Loc: Leeds, UK
Don't forget your big Pioneer sticker in the back window if you go for a blue Clifford LED

The Clifford Alarm on my old Mazda 323 didn't stop them smashing every single window of the car. Scum is just scum, they will in the end break in what ever you try and do.

I have to give the guys who did my Smart Car a bit of credit they did it without leaving a mark on the car. Still Scum

Cheers

Cris.

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#302765 - 02/10/2007 18:36 Re: Wiring an LED (in car) [Re: Phil.]
AndrewT
old hand

Registered: 16/02/2002
Posts: 867
Loc: Oxford, UK
No need for a relay here...
Connect the flashing LED between a constant +12v (or something you find at +12v with the ignition off) and something that goes to +12v with the ignition on. You should find that the latter connection will have enough of a path to ground to run a simple flashing LED (with resistor). With the ignition on the LED won't flash because both ends of the LED will be at the same potential (+12v).

You should be able to do all of this on the back of the ignition switch.

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#302766 - 02/10/2007 18:47 Re: Wiring an LED (in car) [Re: AndrewT]
wfaulk
carpal tunnel

Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
Fancy.
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Bitt Faulk

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#302767 - 02/10/2007 18:55 Re: Wiring an LED (in car) [Re: tfabris]
AndrewT
old hand

Registered: 16/02/2002
Posts: 867
Loc: Oxford, UK
Quote:
Do not do this.


I think that fitting a flashing LED saved me a load of hassle.

I had a 3 yr old car that was broken into (ISTR) four times in the first 18 months I owned it. The after-market alarm that was fitted was triggered by vibration sensing and monitoring of the +12v line's stability, but it had no LED warning. The vibration sensing was turned right down to prevent false alarms on windy days and the voltage sensing didn't always trigger just with the courtesy light. On one occasion the bastards got as far as breaking the steering lock before the vibration triggered the alarm!

After fitting a flashing LED there were only another 2 break in attempts in 10 years and these looked like opportunist thieves trying to see what was in the glove box.

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#302768 - 02/10/2007 19:06 Re: Wiring an LED (in car) [Re: AndrewT]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31313
Loc: Seattle, WA
Maybe. But on the other hand, a flashing LED (or even a real alarm with an LED indicator) will indicate to theives that there's something in the car you felt was worth protecting. Thus, making it a greater target.

Heck, for that matter, I've heard of people who got their alarms stolen...
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Tony Fabris

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#302769 - 02/10/2007 19:38 Re: Wiring an LED (in car) [Re: Phil.]
Robotic
pooh-bah

Registered: 06/04/2005
Posts: 2026
Loc: Seattle transplant
Googling 'fake car alarm' got me several options- home-built and store-bought.
Sorry, I don't have time to review any of the sites, just googled it to see what would come up.

Good luck! I hope it helps the problem!
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10101311 (20GB- backup empeg)
10101466 (2x60GB, Eutronix/GreenLights Blue) (Stolen!)

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#302770 - 02/10/2007 19:59 Re: Wiring an LED (in car) [Re: tfabris]
AndrewT
old hand

Registered: 16/02/2002
Posts: 867
Loc: Oxford, UK
There are two things to protect from theft here: the car and the contents. While a flashing LED might be considered as a suggestion of a nice stereo (or a sat nav or other valuable contents) stashed onboard, an alarm also sends the message that the car is not an easy target "it's alarmed and immobilised, go find an easier one"!

I take your point though; if the LED can mimic a factory fitted alarm then so much the better. Perhaps this contributed to my success with fitting one - I tried as best I could to make it look original even though it wasn't available as a factory option.

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#302771 - 02/10/2007 21:13 Re: Wiring an LED (in car) [Re: tfabris]
cushman
veteran

Registered: 21/01/2002
Posts: 1380
Loc: Erie, CO
Quote:
Maybe. But on the other hand, a flashing LED (or even a real alarm with an LED indicator) will indicate to theives that there's something in the car you felt was worth protecting. Thus, making it a greater target.

It's funny, I have a Volvo with a factory alarm and the flashing LED on the dash looks out of place. The dash is tan, and the bezel around the LED is black so it looks pretty odd. Kind of funny because it's the factory alarm.
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Mark Cushman

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