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Help for Uber Newbie - GPS trigger

Hello all,

I have a car alarm that I want to use the output (say the horn) to trigger a GPS locator so that if the alarm is triggered, it will notify by e-mail that there is an alarm situation. The problem is, arming and disarming produces an output. I need some sort of circuit that will look for a pulse longer than the chirp (or double chirp) that indiciates arming / disarming. Did I mention I'm an Uber newbie? Someone mentioned this may be possible with an RC circuit. The output it would require would be negative, though if someone has a circuit that creates a positive output, I can get around this with a relay. Your help is greatly appreciated.

Reply to
zsoltar
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Pretty simple task to work out the pulse delay thingee. A one shot multivibrator and some logic gates can seperate the short pules from a long one. Of course these days an 8 pin PIC would probably be the best solution. Now getting a pulse to send an E-mail is software magic that I don't have a clue about, but of course I know it can be done.

Reply to
Lefty

Send the email is simple, once you have the hardware figure out. You can have a socket connection to your mail server's smtp port. To do so, you must have hardware like GSM/GPRS radio. Anything can be done, with the right price of course.

Reply to
linnix

As I understand it in general terms, you have a horn "output" that you want to use to control something, if, and only if, that output is active for longer than a "chirp". You mentioned RC and a relay, so this circuit is designed with that in mind.

  • ----+------------+-----+ | | | | 1N4001 [D1] [Rly] Omron G5LE-14-DC12 | |a | | +-----+ | | P --- 500K O
Reply to
ehsjr

Thank you for all your answers to everyone who responded. I had already written a response, but Firefox crashed and I did not get a chance to send it off, so this will be brief. The GPS unit looks for a negative input, which causes a notification to be sent by e-mail. The relay should stay energized for about 5-10 minutes even after the drop in the horn pulse to prevent an overload of e-mail notifications to be sent.

Reply to
zsoltar

Ok, that requires something different. You can still use the TL431 circuit, but have it trigger a timer. Replace the relay with a 1K resistor and eliminate D1, like this:

  • from battery---+-------------------+ | | + ----+---->|----+ | | | D1 | | ----- | P [1K] [10K] +---1| |8-+------+ 500K O to GPS

Build a 555 monostable that is powered from the battery (not the horn - the TL431 circuit still gets power from the horn relay). Tie pin 2 of the 555 to + from the battery through a 10K resistor, and to the TL431 circuit as above. You can find the 555 circuit here:

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A 470 uf cap and a 1Meg resistor for the 555 circuit will give you a long (+) output roughly 8-9 minutes. I drew the circuit above with a 2N3904 transistor to give you a (-) output for the GPS, but you could use a relay if you want.

Ed

Reply to
ehsjr

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