Blinking red light

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PhreakPhy

Limp Gawd
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Feb 2, 2003
Messages
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I am trying to make a fake alarm, with a blinking red LED. But I dont exactly know how to wire my relay. It is RadioShack #275-249.
I would draw a schematic, but i dont exactly know how to do it, and make it understandable. any help wiriing this realy wold be apriciated.
Also, how do I calculate what size resistor to use?
 
You have to clue us in to what exactly you're trying to do. What's the application? What is your source of power? What drives the relay, and what should the relay control?
 
I now realized my mistake of wiring the relay. I dont think it is a problem. The source power is going to be 12v from a car system. The blinking led runs at 5v, 20mA. Well, it did, i poped it with my 9 volt, oops.
 
Iv got it working, but is there anything i can do to slow the blinking? It is allmost too fast to be belivable.
 
If the flashing circuit is in the led there's nothing you can do. You can make your own flashing circuit fairly easily, this tutorial will tell you how to set up a 555 timer for this purpose.
 
If it blinks toof ast using a resistor then add a string of normal leds in series to it and hide them under the dash. This will drop the voltage in a more suitable way than a resistor.

*Works well in this application, no recommended for use in other applications
 
you can buy LEDs with blinking circuitry built right in, my local shop sells them for about $0.60CDN. All you need to do is wire up the proper resistor, and BAM! - Instant fake alarm.

I have one in my car right now.
 
on another note... i wouldn't recommend doing this for a Real alarm, unless the LED is hooked up to a different power supply then your car battery (and then, i definatly recommend it).
 
ive done exactly what you're trying to do with a blinkin' red LED. straight from radioshack. i also bought an aluminum crossover component with a perfectly sized hole in the middle. it was about an inch square, and maybe a quarter inch deep. i bent off the terminals and spray-painted it black, and then stuck the LED in the hole in the middle. the blinking was slow, i thought, about a 1/3 second every second, if im remembering that correctly... so maybe if you're trying to get a slower speed just look for diff types of flashing LEDs. i do remember that the led i used had the lowest power consumption i could find, because i wanted to make the battery (either one or two d cells) last as long as possible. maybe that had something to do with the speed?
 
Originally posted by DatHak512
ive done exactly what you're trying to do with a blinkin' red LED. straight from radioshack. i also bought an aluminum crossover component with a perfectly sized hole in the middle. it was about an inch square, and maybe a quarter inch deep. i bent off the terminals and spray-painted it black, and then stuck the LED in the hole in the middle. the blinking was slow, i thought, about a 1/3 second every second, if im remembering that correctly... so maybe if you're trying to get a slower speed just look for diff types of flashing LEDs. i do remember that the led i used had the lowest power consumption i could find, because i wanted to make the battery (either one or two d cells) last as long as possible. maybe that had something to do with the speed?
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here's my qaulm with this for real alarms on cars and hooking it directly into the car battery, if a theif is smart and shorts out the battery... he knows exactly when the battery is dead without setting off your alarm, cause that light goes off.

if you used one or two d cells like you said though, the theif would think he's failed at shorting out the battery.
 
Originally posted by plot
here's my qaulm with this for real alarms on cars and hooking it directly into the car battery, if a theif is smart and shorts out the battery... he knows exactly when the battery is dead without setting off your alarm, cause that light goes off.

if you used one or two d cells like you said though, the theif would think he's failed at shorting out the battery.
Click to expand...
so you're saying that because he's shorted out the battery and the LED is still blinking, the theif will assume that the alarm is a fake, because how could it still be blinking if the battery is outta the picture? am i undserstanding you right? or if you want the LED to go out with the battery, all you have to do is wire it to the vehicle's battery instead of using a completely isolated circut. this would save on component costs as well...
 
Originally posted by plot
here's my qaulm with this for real alarms on cars and hooking it directly into the car battery, if a theif is smart and shorts out the battery... he knows exactly when the battery is dead without setting off your alarm, cause that light goes off.

if you used one or two d cells like you said though, the theif would think he's failed at shorting out the battery.
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? :confused: ? :confused: ?
An intelligent thief doesn't short out the battery.
A. How will he have access to the battery?? Any socket or terminal within the cabin of the car will be fused which means that the terminal would be independent of the battery once the fuse blows.
B. How will he deal with the fact that unless he slowly drains the car, whatever he uses will easily become scalding hot because of the high current flow.
C. If he does slowly drain the battery, why would he want to stick around?
D. The battery will be dead when he tries to start the car unless he brings another car to jump-start it or brings some sort of independent jump-start battery...
No thief would be stupid enough to do that. Any intelligent thief would look for "easy pickin's" and go for a car without an alarm that can be stolen quickly and quietly.

-special [k]
 
Originally posted by DatHak512
so you're saying that because he's shorted out the battery and the LED is still blinking, the theif will assume that the alarm is a fake, because how could it still be blinking if the battery is outta the picture? am i undserstanding you right? or if you want the LED to go out with the battery, all you have to do is wire it to the vehicle's battery instead of using a completely isolated circut. this would save on component costs as well...
Click to expand...

i'm saying if he's shorted out the battery and the light is still blinking, he won't know he's shorted out the battery... and keep trying until he leaves, even though the battery is already shorted.
 
heh.. well as specialk says it'd be unlikely that a theif would be able to get access to the battery under the hood unless he's already inside the car... but in any case, it sounds like a seperate battary[pack] is the way to go for the LED. as long as you don't forget about it and it leaks battery acid all over your govebox or something:eek: ...then you should be in good shape.
 
Originally posted by DatHak512
heh.. well as specialk says it'd be unlikely that a theif would be able to get access to the battery under the hood unless he's already inside the car... but in any case, it sounds like a seperate battary[pack] is the way to go for the LED. as long as you don't forget about it and it leaks battery acid all over your govebox or something:eek: ...then you should be in good shape.
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nope, very possible to short out the battery with magnets and shit through the hood. or even crawling under the car, you could probably access wires coming from both terminals of the battery... happened to my friends car.
 
hmmm.. didnt think of the "under the car approach." i guess i need to think more often then. so i'll by the under the car deal, but how are you supposed to short out a 12v lead-acid car battery with a magnet?!
 
ummm, shorting out a car battery = welding, fire or explosion. It's not like a D cell. I've seen screwdrivers melted into a million blobs of shrapnel. I don't buy that as car robbery method. Chances are the resulting smoke and flames are going to demand a little more attention than an audible alarm. And if thieves in your area are that stupid, I'd be looking into better ways to protect my stuff than a fake blinking light, like maybe hiring an armed guard or something. Just my opinion.
 
The thief obviously drains it slower with a resistance, not a complete short.

And as for the magnet, I assume they maneuver some resistive conducting device over the batt. terminals using the magnets, not by sucking energy out via magnetism ;)
 
and thus we come to the conclusion that the carjacker's name is not, in fact Theif, but that his name is Houdini...

-Sherlock Holmes
 
Originally posted by mattg2k4
The thief obviously drains it slower with a resistance, not a complete short.
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Well, considering that the average battery could power a high resistance load like headlights accidentally being left on for several hours, and even at that point there could probably be enough energy to power a blinking led for some time, I hope there is a bar or pool hall nearby for the would-be criminal to occupy his time whilst he counts down the joules.
 
Think outside the box. It is soo ez to short out a car battery.
1. Bust out a head lamp
2. Hook up a high powered stun gun to the terminals of the busted head lamp.
3. Shock the crap out of it and hope that the stereo is well fused.

This aproach will normaly blow the fuse to the caralarm, and fry the cars ECU. Alarm disabled.

As far as the blinking red light goes. I got mine working great, and it looks very real. A car theif that sees a blinking red light that looks real, and trys anyways, probably knows many ways to quickly disable your car alarm. Like anything else, this is just a deterant. It should stop most casual stereo theivs.

And for the battery tihng. I have heard of it from a friend. I dont know exavtly how it works, or what to do, or if it even realy works. But I can imagine a fiew ways of it working.
 
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