Need simple timer module or kit for car alarm project

[[email protected]]

Hi, my car was just broken into yesterday, so I decided it's time to
get a car alarm. It's an old car, so I bought a cheap (but good brand)
basic vibration sensing alarm. Being the tinkerer I am (and not wanting
to irritate my neighbors with false alarms), I want to install a timer
that will wait a little bit before sounding the siren.

I also bought another cheap alarm system ($20 on eBay) that instead of
a siren sends a message to a pager. Thus, assuming both alarms trigger,
the neighbor annoying siren won't go off immediately, but I will still
be informed. Ideally, these two systems should be combined, so that I'm
using the good brand vibration sensor to activate both the siren and
pager, but I'll leave that project for later. (Incidentally, I'm also
going to install a homemade fuel pump kill switch, but this won't be
connected to the alarm system.)

I'm thinking I'd need to put an initially open relay in series with the
siren and the timer in parallel. When the circuit closes (i.e. alarm
tries to go off) the timer gets activated and closes the relay after a
certain (hopefully adjustable) amount of time. When the alarm tries to
turn off the siren (i.e. I hit the stop button on the alarm's remote),
this will kill power to both the timer and siren. Doing so will reset
the timer so it's ready for next time. I suppose I could also live with
a timer that needs a manual reset using a button or whatever.

Anyone know where I can get such a timer? This timer needs to be
inexpensive, as I'm disabled and living off public assistance.

Before becoming disabled, I was a computer science major at UC
Berkeley, so I have basic electronics knowledge. My experience with
soldering, however, is limited to a single light sensing switch I made.
(That was a fun project, intended to operate a window shade that would
open with the morning sun.)

 

[jasen]

Incidentally, I'm also
going to install a homemade fuel pump kill switch, but this won't be
connected to the alarm system.

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


Bye.
Jasen

 

[Guest]

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.

 

[Guest]

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.

http://www.kpsec.freeuk.com/555timer.htm

 

[[email protected]]

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

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!)

 

[jasen]

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.

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.

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.

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

'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?

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

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.)

Before.

ign +----> to other equipment
switch |
|

 

[ehsjr]

Hi, my car was just broken into yesterday, so I decided it's time to
get a car alarm. It's an old car, so I bought a cheap (but good brand)
basic vibration sensing alarm. Being the tinkerer I am (and not wanting
to irritate my neighbors with false alarms), I want to install a timer
that will wait a little bit before sounding the siren.

I also bought another cheap alarm system ($20 on eBay) that instead of
a siren sends a message to a pager. Thus, assuming both alarms trigger,
the neighbor annoying siren won't go off immediately, but I will still
be informed. Ideally, these two systems should be combined, so that I'm
using the good brand vibration sensor to activate both the siren and
pager, but I'll leave that project for later. (Incidentally, I'm also
going to install a homemade fuel pump kill switch, but this won't be
connected to the alarm system.)

I'm thinking I'd need to put an initially open relay in series with the
siren and the timer in parallel. When the circuit closes (i.e. alarm
tries to go off) the timer gets activated and closes the relay after a
certain (hopefully adjustable) amount of time. When the alarm tries to
turn off the siren (i.e. I hit the stop button on the alarm's remote),
this will kill power to both the timer and siren. Doing so will reset
the timer so it's ready for next time. I suppose I could also live with
a timer that needs a manual reset using a button or whatever.

Anyone know where I can get such a timer? This timer needs to be
inexpensive, as I'm disabled and living off public assistance.

Before becoming disabled, I was a computer science major at UC
Berkeley, so I have basic electronics knowledge. My experience with
soldering, however, is limited to a single light sensing switch I made.
(That was a fun project, intended to operate a window shade that would
open with the morning sun.)

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.
http://www.allelectronics.com/
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

 

[[email protected]]

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

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

 

[jasen]

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

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.

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

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

Bye.
Jasen

 

[[email protected]]

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

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.

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

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?

 

[Rich Grise]

On Mon, 26 Jun 2006 20:05:16 -0700, googlegroups wrote:

(Incidentally, I'm also

going to install a homemade fuel pump kill switch, but this won't be
connected to the alarm system.)

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