Headlight Accent LED & Car Alarm LED

reviewum

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Hi All,

I'm not sure where to post this, but since it is "homemade and modified" I thought this is the place.

I'm running out of flashlights to modify (yes, I believe you can have too many flashlights... please don't punish me /ubbthreads/images/graemlins/cool.gif )... and I thought I'd look for something else to stick LEDs into.

I have a bunch of blinking RED LEDs and I'd like to put one in my car as a car alarm warning light (many people add LEDs as Fake car alarms which is a great idea!) I have an alarm in my car, but no light! I'd like it to be on only when the car is OFF, but am not sure how to do it. Any ideas?

I'm also thinking about sticking some of these (or my blue ones) into the headlights for fun. I'm not sure if I want the on all the time, but I guess I could since the draw is so low. I saw something like what I want to do here:
http://www.superbrightleds.com/instructions.htm

I guess my main question is in regard to the car alarm light and how to get it to turn on and use the car battery when the car is off. Any suggestions or comments on the car alarm, or accent headlight leds would be greatly appreciated!

Thanks in advance!
 

Saaby

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As to the car alarm, you need to wire in some relay that closes (Provides power) when the car is off. This could be accomplished with a relay held open by the switched 12V that, when closed, switches the unswitched 12V on to the blinker LED. I'd put the blue ones for your headlights on their own switch if you have a blank on the dash. What kind of car?
 

reviewum

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Thanks for the posts!

tylerdurden- Is the blue light an issue when the car is not running? I think the light will be too dim to be seen when the headlights are on. I just wanted a cool effect while the car is off.

Saaby- I'll take a look at Radio Shack for a relay that might work. The car is my 2001 Hyundai Elantra GT. I've already done some simple mods here:

http://www.nifty-stuff.com/gt-lights.php
and
http://www.nifty-stuff.com/gt-lights-seats.php
 

ResQTech

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I was thinking about putting 1 watt white LS's in my driving lights to have a clean white glow at night when the driving lights are not in use, what do you all think? Probably wont be visible enough during the day to serve at DRLs.
 

MenaceSQL

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[ QUOTE ]
MTFD17 said:
I was thinking about putting 1 watt white LS's in my driving lights to have a clean white glow at night when the driving lights are not in use, what do you all think? Probably wont be visible enough during the day to serve at DRLs.

[/ QUOTE ]

The heat generated from the headlight bulbs might be too much for the luxeon. Maybe an expert can chime in on this.
 

CNC Dan

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[ QUOTE ]
Saaby said:
As to the car alarm, you need to wire in some relay that closes (Provides power) when the car is off. This could be accomplished with a relay held open by the switched 12V that, when closed, switches the unswitched 12V on to the blinker LED.

[/ QUOTE ]
That's the hard way. Find a source of +12v that is on when the car is off.(clock power?) Then find a source of +12v that is only on when the car is running and always uses power.(daytime running lights? ignition?) Wire your blink led/circuit using the first wire as your POS. connection and the second wire as your NEG. connection. When your car is on both sides of your circuit get +12v so no current flows. Whe the car is off, the switched +12v goes to 0 volts and your circuit sees +12v and 0v and begins to flash.
 

reviewum

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[ QUOTE ]
CNC Dan said:
That's the hard way. Find a source of +12v that is on when the car is off.(clock power?) Then find a source of +12v that is only on when the car is running and always uses power.(daytime running lights? ignition?) Wire your blink led/circuit using the first wire as your POS. connection and the second wire as your NEG. connection. When your car is on both sides of your circuit get +12v so no current flows. Whe the car is off, the switched +12v goes to 0 volts and your circuit sees +12v and 0v and begins to flash.

[/ QUOTE ]

CNC Dan - Will that work without blowing up / melting / draining anything? I was about to try a relay, but if your idea will safely work, then I may try that. I guess the volts, current, etc. from both sides must be exactly the same right?

Any comments on this approach?
 

tylerdurden

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[ QUOTE ]
reviewum said:
tylerdurden- Is the blue light an issue when the car is not running? I think the light will be too dim to be seen when the headlights are on. I just wanted a cool effect while the car is off.


[/ QUOTE ]

I'm not a lawyer, but I believe if the car is parked on private property, you can do whatever floats your boat.
 

reviewum

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[ QUOTE ]
tylerdurden said:
I'm not a lawyer, but I believe if the car is parked on private property, you can do whatever floats your boat.

[/ QUOTE ]

I'm not too worried about it. From what I know it is only a problem when your driving / running lights are blue. Since I don't plan on driving without my headlights on, I don't think it will be an issue. My main problem now is how to get my LED into the headlight assembly without too much trouble.

Regarding the blinking LED, I have the same problem with where to put it without drilling holes into my dash, but still making it look good.
 

fred0109

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I did this same thing years ago in my old truck.(blinking alarm light) I took a red blinking LED from radioshack and wired in a 1K ohm resistor on the positive side and simply found the fuse in the panel for the ignition. This will turn on when the car is turned off, and the LED will be off when the car ignition is switched on. All very simple really, no relay needed. Hope this will help.
 

reviewum

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I found the fuse for the ignition, but I have no idea how to get at the wires. Did you pull the fuse out and rig something, or did you just follow the wires and splice into them?

I may just use a battery and manually turn the dumb thing on until my warranty expires! :)
 

fred0109

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All I did was pull the fuse and loop the wire around the metal spade then replace. I never had any electrical problems with this, however if I were to do it again I would use a slip-on fuse connection. I think you can buy them at radioshack or some place like that. They slip over the spade and have a terminal connector that comes back over the top of the fuse. I really have never bought them, but see our installers using them at work. They are not good for high amp-draw equipment, but fine for LED stuff.
 

CNC Dan

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[ QUOTE ]
reviewum said:
CNC Dan - Will that work without blowing up / melting / draining anything? I was about to try a relay, but if your idea will safely work, then I may try that. I guess the volts, current, etc. from both sides must be exactly the same right?
Any comments on this approach?

[/ QUOTE ]

If you have the LED already set to work on 12V then this will work just fine. The small current that goes back 'into' the second wire described, is so small that it won't effect anything. However, you should add a fuse so that if any or your wires chafe on any metal the fuse will blow, rather than melt the wires.
 

reviewum

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Okay everyone... my impatience got the best of me so I did a temporary fix until I decide on a more permanent solution.

Here it is:

Car Alarm Blinking LED

alarm-1.jpg


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

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

MATERIALS:
1 - bright red 5mm Blinking LED from eBay: ($.20)
1 - bright white 5mm LED from eBay: ($.20)
1 - C cell battery clip: Radio Shack: ($2.50)
1 - 75ohm resistor. ($.10)
2 - Cannibalized computer switches. One power button, one reset button.

Total Cost: $3.00

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:
alarm-8.jpg


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".

alarm-6.jpg


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

I've placed this on my site here:
http://www.nifty-stuff.com/car-alarm.php
 

Saaby

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Loooks good, and a restored, blinking red LED on D batteries may well last until your warranty runs out /ubbthreads/images/graemlins/tongue.gif
 

reviewum

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That's a good point / question! How long do you think this light will last on two C batteries?

I've got two C batteries, a 75 ohm resistor and a blinking LED like the one here:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2578171220&category=26207

I had a hard time reading the MA draw on my meter with the flashing and all. The current was all over the place, from 0 - 7ma. How do I determine the draw and how long does a typical alkaline C battery last in MAH? (BTW, why don't they print the MAH on alkaline like they do on NIMH?)
 

Tomas

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Same thing CNC Dan said...

Excuse the vagueness of this but I'm going back to an LED I had in a vehicle of mine about 5 vehicles ago.

I don't recall the value of the resistor I used, but it was the value I'd have used to limit current assuming 14VDC to the LED.

One side of the LED (a red Radio Shack LED with a built-in flashing circuit) was connected through the resistor to an unswitched +12V source (always on) and the other side was connected to the switched accessories lead from the ignition switch. The LED was mounted in a convienient position attop the dash. *

When the ignition was on (or turned to the accessory position), the voltage on both sides of the LED was the same +VDC. No current flowed. (LED OFF)

When the ignition was switched off, the accessories in the vehicle that were usually left on (for me usually the air blower, radio, etc.) offered a low resistance path on that side of the LED to ground. (LED ON
disco.gif
)

What this did was prevent the LED from being on when the ignition was on (therefore no distraction while driving) but powered it up immediately when the ignition was not turned on and not turned to the accessory position ...

It worked well, was cheap, and a 20mA drain on a car battery is essentially nothing ...

That was the cheapest, and easiest to use 'car alarm' I ever had.

T_sig6.gif


* I think the points I actually used were the power lead to the headlight switch for "always hot" and the power lead to the radio for "accessory." They were the easiest for me to get to in that vehicle. For connection I used some of those neat 3M connectors for tapping onto an existing wire.
 

reviewum

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Tomas- Thanks for that excellent description and for backing up what Dan said! This opens up a whole new way for me to explore electicity... I never thought about wiring something to cancel itself out. When I'm feeling a bit more daring I think I'll give that a try.

Regarding the runtime on my temporarry blinking light: Anybody have any idea on how long it will last? My problems again are:

1) I don't know the MAH on these (or any) alkaline batteries.
2) My meter is having a hard time reading the current draw.

Thanks!
 

reviewum

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It's still blinkin' away...

My wife thinks it is blinking too fast and asked if I can slow it down... since the blinking is built into the LED (how do they do that anyway?) I don't think I can change it.

Also, any comments on how long this blinking LED will run on my C cell batteries, or how I can measure it?

Thanks!

p.s. "this blinking LED" sound like I'm swearing! :)
 
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