Morris Minor Owners Club

I’m thinking aloud here, I am going to buy a free standing shed alarm, that detects movement and sounds a siren. Now I’m thinking it would be handy if I could somehow link a mobile phone, that in the event of the alarm sounding, would dial my number. How could I get the sound of the alarm to cause an additional phone to ring my number ?
Ive set a phone to speed dial, with two wires coming out, so that only two contacts need to be made. Is something like this possible ?

I suppose it depends on the alarm and if it gives a switched output for an external sounder.
If it doesn't and you don't mind opening it and voiding warranty, you may find a switched supply inside to the sounder or even to power an "alarm triggered" LED.
Any of the above could power the coil of a Reed Relay, they draw very little coil current about 10mA and the switch contacts could be connected to your phone speed dial wires that you have added.
I had a quick google and the coil details of some are;-
5V with a resistance of 500 ohms that would draw 10mA
12V with a resistance of 1000 ohms that would draw 12mA
That would rely on your phone not being bothered about having the speed dial button held down, that could be worked around though by having a suitable capacitor in series with the coil to give a pulse of the switch contacts.
Just my thoughts, also thinking aloud!
Regards John

Thanks John I guessed it would get involved. Once I get the alarm I’ll explore the feasibility of looking inside.
I have been building a circuit board that links to a phone, using one of those 555 timer IC’s to give a pulse but again it got a bit beyond me.

I've made a few useful circuits using the 555 timer I/C but wouldn't know how to link it to a phone.
That's why I thought a Reed Relay might be doable. A bit more old school.
You can get sound activated alarms but many of them are kits and you still need to find a way to link it to your phone.
Another option would be an alarm with an auto dialer built in, I'm not sure how the SIM card part of those work, it may be an extra ongoing expense.
Perhaps other more knowledgeable members will know....
Regards John

Thanks for those thoughts and options. I might have a rethink about the IC circuit.

https://www.henrykrank.com/door-mine-se ... evice.html
https://www.henrykrank.com/alarm-mine.html
https://www.henrykrank.com/12g-black-po ... ck-12.html

For a louder alarm you need some...

https://www.henrykrank.com/pyrodex-p-1lb-454g.html

If you use the full 454g then it is likely the Police will arrive quickly.

I found this...."How to Make a DIY Alarm/Tripwire"
https://www.instructables.com/id/DIY-Alarm-with-Phone/

That’s interesting, I’ve got the phone sorted with the two wires, I’m not too struck on the priming method though seems a bit of a rigmarole. Thanks for posting!

The link Berni posted reminds me of a setup one of my Dads mates had in the 70's.
It involved a blank 12 Bore gun cartridge

Blank twelve gauge cartridge alarms still available . Triggered by a trip wire ! I have a couple !!!

StillGotMy1stCar wrote: ↑Sat Sep 28, 2019 5:41 pm The link Berni posted reminds me of a setup one of my Dads mates had in the 70's.
It involved a blank 12 Bore gun cartridge

Credit where it's due, the Big Bang links are Rob Thomas'...