flashing led in car

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rwdbmwm3

Member - Posts: 8

Joined: December 16, 2007

Location: Canada

Posted: December 16, 2007 at 8:45 PM / IP Logged

I was just wondering what the best way to do this would be

(like the flashing LED's with cars that have alarms)

there is a circuit you can make with a 555 timer and 1.5V battery...how long would the battery last on this sort of circuit?

and there is also something you can buy from store... an led that runs off of your 12V car battery or something like that?

im looking for an effective way to do this that will last the longest... maybe someone can explain to me how the ones in cars work and i can just use same concept...instead of buying new things just tap into car 12V source and wire up something to do to make the circuit work forever

thanks

tedmond

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Joined: January 06, 2007

Location: Ontario, Canada

Posted: December 16, 2007 at 9:19 PM / IP Logged

u can go buy a flashing led @ radio shack that will work off a 9volt battery or een the 12v car battery itself. look for the post about flashing LED, there are maybe circuits u can build that will allow the function of flash or simply buy the flashing LED premade; just wire and thats it

rwdbmwm3

Member - Posts: 8

Joined: December 16, 2007

Location: Canada

Posted: December 17, 2007 at 9:29 AM / IP Logged

how long does it last though? thats the most important thing ....

i remember when my friend bought a muliple flashing led fake alarm thing..ran off a 1.5V battery, lasted 1 night......

tedmond

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Joined: January 06, 2007

Location: Ontario, Canada

Posted: December 17, 2007 at 9:10 PM / IP Logged

an LED has a lifespan of 10 000 hours of usage. If u were to run that off a 9 volt battery, it would sure as hell last u a long time. I remember using one before off the 9 volt and it lasted for 2 - 2 and ahalf years. if u used it off ur car battery, who knows when it would die out. LED draw very little current.

rwdbmwm3

Member - Posts: 8

Joined: December 16, 2007

Location: Canada

Posted: December 18, 2007 at 7:18 PM / IP Logged

tedmond wrote:

nono i dont mean the MTBF of the LED .. i mean how long will it last when hooked up to the battery...

Like i said, my friend bought a little led circuit thing that 5 led's went right to left... 1.5V battery drained over the course of the night

for example if i was using the 555 timer circuit, how long would the battery last me (constant use 24/7)

rwdbmwm3

Member - Posts: 8

Joined: December 16, 2007

Location: Canada

Posted: December 18, 2007 at 10:28 PM / IP Logged

rwdbmwm3 wrote:

tedmond wrote:

nono i dont mean the MTBF of the LED .. i mean how long will it last when hooked up to the battery...

Like i said, my friend bought a little led circuit thing that 5 led's went right to left... 1.5V battery drained over the course of the night

for example if i was using the 555 timer circuit, how long would the battery last me (constant use 24/7)

Also someone said

"12.8 volts minus 3.2 volts equals 9.6v drop across the resistor. The current is 30 mA, so use Ohm's Law to figure out that Resistance = Volts divided by Amps.

resistance = 9.6v / 0.03 amps

resistance = 320 ohms."

if you have 2leds is it 6.4/60ma? or 6.4/30ma

or 3 leds.... 3.2/ what

KPierson

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This member consistently provides reliable information

Joined: April 14, 2005

Location: Ohio, United States

Posted: December 20, 2007 at 9:26 AM / IP Logged

You should be able to find some LEDs that pull less then 5mA of current and are plenty bright enough for what you are using it for. 5mA will lasts for weeks on a standard car battery. Of course, the longer the off time compared to the on time the longer the battery will last. Most aftermarket alarms don't have a 50/50 on/off time, more like 75% off and 25% on. This extends battery life quite a bit. OEM LEDs can be 10:1 or even higher for minimal current consumption.

You can get a 555 timer and a few other components and make a pretty decent flashing circuit. You can then tap the igntion lead for ground (most igntion systems rest at ground when key key is off) and hook it up to constant power. This will give you a control circuit that will only flash the LED when the key is off.

If you want to get a bit more sophisticated you can program a microcontroller to turn on and off based on lock and unlock pulses that will completly mimic an OEM or even aftermarket LED.

Kevin Pierson

mystic knight

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Joined: November 14, 2005

Location: United States

Posted: December 23, 2007 at 10:57 PM / IP Logged

I'm not sure why you're planning on running it off a battery. If it's going into a car you may want to consider using one of the 3 wire Varad led's and wiring it to the car. Then it'll be running off the car battery. Having a little flashing light in your car even when your driving would probably get pretty annoying. And if you wired in a switch you'd always have to make sure you turned it on and off.

http:////VARAD-LL-RE-SUPER-BRIGHT-RED-FLASHING-LED-for-ALARM_W0QQitemZ170179480396QQihZ007QQcategoryZ33713QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

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flashing led in car

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