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Anti-theft alarm device idea

Strickers97

Strickers97

Accelerating Away
Having thoughts of creating my own car alarm.

Thinking of having a plunger switch on the driver's door that sets off a 10s timer when the door is opened. The timer will be hooked up to a horn in the engine bay. Will wire in a switch on the dash that needs to be flicked off in order to turn the whole thing off. Problem is I can not find a suitable timer.

In practice if the door is opened you have 10s to flick the switch before the car horn comes on. Hopefully should deter someone from breaking in and nicking stuff.

Need something that will delay on after a 12v pulse from the plunger switch on the door. Does anyone know of such a thing?
 
Strickers97 said:
Having thoughts of creating my own car alarm.

Thinking of having a plunger switch on the driver's door that sets off a 10s timer when the door is opened. The timer will be hooked up to a horn in the engine bay. Will wire in a switch on the dash that needs to be flicked off in order to turn the whole thing off. Problem is I can not find a suitable timer.

In practice if the door is opened you have 10s to flick the switch before the car horn comes on. Hopefully should deter someone from breaking in and nicking stuff.

Need something that will delay on after a 12v pulse from the plunger switch on the door. Does anyone know of such a thing?
Click to expand...
I’ve always found 12vplanet technical staff very helpful
 
Thought about that but that is a delay off switch. As in it stays on for a certain about of time after being triggered.

I need one that will turn on after a delay. Also need it to be triggered by a single pulse from the plunger door switch, as in needs to stay on after being triggered no matter how many times the trigger switch is re-pressed.

I'll draw a diagram once I find a pencil and spare paper
 
The delay 'on' solenoids are hard to find at a good price, for some reason the delay 'off' are much cheaper,
one from amazon may do the job, search '12v delay turn on module' they are about £7 delivered,
atb
 
You'll also need to think carefully about the 'arming sequence' when you set the switch back to 'alarmed' and open then close the door on exit from the vehicle. Don't want the siren going off then!

I suspect you'll find the logic needing to be done in relays, switches and timers is too much and you might as well buy a proper alarm.
 
It might be a good idea. My brain likes to go through the daft DIY options before admitting defeat and buying an off the shelf solution.

Might stick to a more simple solution whereby all the doors have switches linked in parallel to a horn and there is a switch on the outside somewhere to disarm the circuit. If you don't press the switch before opening a door the horn goes off. Will alert me and scare the s**t out of them.
 
I looked at door switches to put an interior light in my 109 but the wiring is more work than I reckoned was worth it. In the end I bought a cheap 12v PIR sensor which spots anyone moving inside regardless of which door they came in through. I then did the logic (dark / not dark, engine on/off, timing) with a £5 Arduino style microcontroller. I reckon they're cheaper and more reliable than relays and way more flexible for almost any application these days.
 
As above, this all sounds like a simple job for a little microcontroller and a bit of wiring. Arduino and the like are so cheap now, the sky is the limit really for home brew stuff.
 
You also have to consider how you will exit the vehicle as when you set the switch and open the door to get out, you will activate the alarm.
You would need another delay timer to allow exit before arming the system.
Starting to sound complicated.
External switch (or remote) would be a better option..?
 
Already have a range of anti start car measure such as remote battery isolator, keyed fuel solenoid, pedal lock and steering lock. Need something to stop some scrot from just opening the door and helping himself, or herself, have to be pc, to any of the car's contents.

A horn or alarm activated by a door opening seemed a good idea. Motion sensor is also another solid shout. A colleague in work recommended a hyperdermic needle full of bleach in the driver's seat, suffice to say I won't be borrowing his car anytime soon, sounds like a Saw film.

Does anyone know if there is a decent, and cheap, alarm I could fit to a series?
 
Tbh an alarm wont stop the door being forced or window smashed to get at your valuables,
Its good door and window locks that you need for that.
The best deterrant is to have nothing whatsoever of value visible from the outside, my pal doesnt lock his cab anymore due to the damage of past nocturnal break in attempts.
Anyway, basic alarms with a horn, module,key fob x2 and door switch (switched earth) and inc the all important 'this vehicle is alarmed' sticker are about for £15, combined with your other measures one should do the trick, i have used them on my vans and they are good for the ease of fitment into basic, older vehicles.
 
I have exactly this on my S2a. 2 door switches, a secret switch, and a unit with a timer that triggers the horn. I got a 1960's car alarm of e-bay, Sparkrite AT20, its perfect for a Series. Search boot sales, there were loads about and the AT20 is the most basic but it does the job. The wiring diagrammes are on the web.
 
Just had another crazy idea! For context, I have had two cars stolen, one shortly after I was dragged out of it, so please feel free to call me paranoid.

I have a fuel cut off solenoid wired up to a keyed switch in the dash. Key has to be turned for fuel to flow. But how will this stop someone dragging you out and knicking the car when it's already running?

Suddenly had a thought about those remote keyless entry jobos on fancy modern cars. Does anyone know of a switch which is normally closed but opens when a remote/card is nearby?

Idea is card is in pocket/wallet. Scum drags you out of car and drives away, but fuel cuts off when the car moves away from you. Bit inspector gadget/James bond I know, but I have a dull office job and time to scheme up these crazy ideas.
 
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