Need simple timer module or kit for car alarm project

don't foget to wire the switc to the fuel gague too :)

Bye. Jasen

look up 555 timing Circuits. Its a little chip that is in loads of timing devices. loads of circuits using a 555 on the net. All the best.

look up 555 timing Circuits. Its a little chip that is in loads of timing devices. loads of circuits using a 555 on the net. All the best.

To make it look like I'm out of gas? That might be a good idea... Also, I was thinking of putting a timer on the kill switch too. That way the perps will actually be able to get into traffic before the car dies on them, thus forcing them to abandon it instead of still having time to find the kill switch.

Or, I was thinking of making it so applying the brakes kills the engine. This will make it look exactly like how the van used to actually behave when its fuel pump was on the fritz.

'Course all this is getting a little weird. Better K.I.S.S. and not mess up my only transportation too bad! I'm already kinda worried about the simple kill switch actually... like does it need a fuse? What about causing a spike? What amp and voltage rating does the switch have to be? Etc. Etc. I *just* put in a new fuel pump and don't want to have to do that again! (Or strand myself somewhere... had enough of that already.)

Kanon

(P.S. I'll look for info on the 555. Thanks!)

I did it to my first car, the carburettor held enough fuel for about 10 seconds driving, if your car is fuel injected then yeah a timer would be a good idea.

engine dies at the first stop light/sign :) sounds good.

the fuel gague also gives the user a clue if they forgot to press the button for some reason

use a relay 10A contacts would be plenty, but 40A lighting reays are plentiful.

Before.

ign +----> to other equipment switch | | >--oxo--+----------------------------> to fuel pump . . existing fuse. After. +--> | | --- hidden push-button +------o o---. | | | _-~ | >--oxo--+--o-~: 0---|----------+--->

: | | |\\~~|----+--+--|

I don't think you really want a delay between the time a vibration sensor is distrubed and the siren goes off. Normally, the kind of delay you want is a delay between the time you turn the alarm on, and the time it arms, to allow yourself time to get out of the car and lock the door. That prevents the siren when you shut the door on exit. Opening the dorr should not disturb the vibration sensor enough to trigger the alarm.

There are many ways exit delay can be done. I'll show one that is the simplest and cheapest way, or close to it. The ACC line is a line that goes to +12 when the ignition switch is turned on. The +12 line is +12 regardless of the ignition switch. The circuit shown gives you roughly 10-15 seconds to exit the car from the time you turn the ignition switch off.

+12 ----------------------------o o \\ < Alarm on/off switch ACC --[.1R]--+-----+----+.... o | | |+ .+ | [Relay] [D] [C] TVS | | |+ | . | Gnd --+------+-----+----+.... [Alarm] | | +---- < relay contact | ^ normally closed | | | +-----------------------+

The relay is an Omron G6R-1-DC12 with a 655 ohm coil and contacts rated 5A at 30 VDC. D is a diode like a 1N4004. C is a 3300 uf electrolytic, which will give you roughly 10-15 seconds delay from the time you turn the ignition off until you turn the alarm on, exit the car, and lock it, before the alarm arms. You can put more capacitance in parallel to increase the time if you want.

The parts are available at Allelectronics.

The cap is CAT #3300/25VA for 90 cents, the relay is CAT # RLY-428 for $1.75, and the 1N4004 is CAT# 1N4004 at 9 for $1.00. The .1 ohm 10 watt resistor is needed if you use the TVS, and is CAT #.1-10 at 2 for $1.00.

You might want to add a transient supression diode - Mouser part #576-1.5KE22 - in parallel with D but oriented with (+) to (+) and (-) to (-) (D is oriented backwards). It's shown dotted in on the schematic as TVS. I haven't found the TVS necessary, but some insist on it. If you don't use the TVS, you don't need the .1R

Ed

Ah, very true. For this, I guess I'd need two relays connected to the same switch, right?

Thanks for the great diagrams! Do the diodes need to be a special kind?

Ed, thanks for your diagram also. I can see this kind of timer coming in real handy!

Kanon

it depends on what you need to do to zero the fuel gague.

relays are available with two sets of contacts ("dual pole"), one set could be responsible for the fuelpump and the other for messing with the apparent fuel level.

or you could run a second relay off the output of the first. (or connect the coil in parallel with the first one's and get the same effect.

any general purpose rectifier diodes should be fine, eg 1N4000.

Bye. Jasen

Well, the fuel gauge is controlled by a potentiometer sending unit in the gas tank. Opening that circuit should make an infinite resistance, which will probably read as empty. I'll play with it.

Cool, thanks for the info. First though, before any of this fancy stuff, I'm gonna just put in a simple kill switch. No relays or anything. I got a 30A switch that I'm going to connect to the fuel pump's inertia switch circuit (the inertia switch kills the fuel pump in case of a collision). Think this will need a protecting diode or fuse?

(Incidentally, I'm also

That should be all you need, and it's kewl - the car will run for about a block on the gas that's left in the fuel line and stuff, and then die in the middle of all of those witnesses as the thief tries to run away. ;-)

Good Luck! Rich