B
Ben Lessani
Hi all,
I've been hunting through car alarms for sale and I have realised they
are damned expensive for what they are. I started reading about 555
circuits and a variety of other topics that may be usefull in the
design of an alarm.
I have come up with this so far,
http://www.geocities.com/blessani/Final_Design.JPG (only 90K, dont
worry)
(You may need to open a new window and paste that address in,
geocities can be a touch irritating)
The whole alarm will be run off the 12V battery that is in the car, it
is very rudimentary and uses simple circuits to complete the final
project. After the 12V supply from the battery is a 9.6V battery - the
purpose of this is to provide a backup facility incase the main wire
is snipped.(I know it would make a lot more sense to buy an alarm -
but I dont want to, I want to attempt to make one for both the fun and
practical aspect).
The alarm will be (in theory) started by the short pulse of the
central locking pump. When I lock the doors (remote central locking),
a signal will be sent from the RF unit to the central locking vacuum -
but only a brief one.
The first use of the 555 is to de-bounce the signal sent, when the pin
3 is armed, it will, in turn arm a toggle switch (to keep the pulse
sent from the RF unit on until the second pulse to stop it) When this
switch is closed, it closes a relay which passes a current through the
monitoring section of the alarm. The blinking LED is to act as a
deterent to theives. The vibration switches will have to be armed 3 or
4 at a time (3 on the diagram), this is so rain or bumps to the car
won't trigger the alarm. They can be sat in various locations within
the vehicle. If any one of these switches closed, then the next part
of the circuit is armed, the timer. This is a 555 monostable timer set
to 33 seconds, it should (in theory) close the next part of the
circuit to let the siren go off for a fixed time period.
The relay arms the disruptive part of the alarm (sirens, indicator
flashes, headlight flashing - whatever springs to mind). The very last
astable circuit is to provide a pulse of 1s, this will continue to run
as long as the 33 seconds continue.
The alarm should all work in theory but I don't know about in
practice, it would be nice if one of you could review the design and
point out flaws etc, before I go and buy the components.
Sorry for the huge post, only way I could explain my first ever
circuit diagram - I don't know if its correct or not.
Ben Lessani
Please gimme a bell by email if you leave a post
([email protected])
I've been hunting through car alarms for sale and I have realised they
are damned expensive for what they are. I started reading about 555
circuits and a variety of other topics that may be usefull in the
design of an alarm.
I have come up with this so far,
http://www.geocities.com/blessani/Final_Design.JPG (only 90K, dont
worry)
(You may need to open a new window and paste that address in,
geocities can be a touch irritating)
The whole alarm will be run off the 12V battery that is in the car, it
is very rudimentary and uses simple circuits to complete the final
project. After the 12V supply from the battery is a 9.6V battery - the
purpose of this is to provide a backup facility incase the main wire
is snipped.(I know it would make a lot more sense to buy an alarm -
but I dont want to, I want to attempt to make one for both the fun and
practical aspect).
The alarm will be (in theory) started by the short pulse of the
central locking pump. When I lock the doors (remote central locking),
a signal will be sent from the RF unit to the central locking vacuum -
but only a brief one.
The first use of the 555 is to de-bounce the signal sent, when the pin
3 is armed, it will, in turn arm a toggle switch (to keep the pulse
sent from the RF unit on until the second pulse to stop it) When this
switch is closed, it closes a relay which passes a current through the
monitoring section of the alarm. The blinking LED is to act as a
deterent to theives. The vibration switches will have to be armed 3 or
4 at a time (3 on the diagram), this is so rain or bumps to the car
won't trigger the alarm. They can be sat in various locations within
the vehicle. If any one of these switches closed, then the next part
of the circuit is armed, the timer. This is a 555 monostable timer set
to 33 seconds, it should (in theory) close the next part of the
circuit to let the siren go off for a fixed time period.
The relay arms the disruptive part of the alarm (sirens, indicator
flashes, headlight flashing - whatever springs to mind). The very last
astable circuit is to provide a pulse of 1s, this will continue to run
as long as the 33 seconds continue.
The alarm should all work in theory but I don't know about in
practice, it would be nice if one of you could review the design and
point out flaws etc, before I go and buy the components.
Sorry for the huge post, only way I could explain my first ever
circuit diagram - I don't know if its correct or not.
Ben Lessani
Please gimme a bell by email if you leave a post
([email protected])
