cctv

hello all, new to site would realy be greatfull for any help or views on following, i am in process of building home burglar alarm system and would like to know what device would activate a mobile gsm phone to ring a last dialed number, my other gsm phone that would allert me when my house alarm has been triggerd, was looking for device that i would be able to build myself and ad to alarm pannel, many thanks, cctv.

akg

most of the gsm phone has a built in modem that can the controlled be At command set . so if you can give that command to the phone (interface depends on the make) , it can dial a no

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cctv

aKG, thanks for info, have only limited electronics experiance but gather that you were saying to programe gsm phone to accept external command to ring when house alarm has been triggerd, how do i programe gsm also what device attached to alarm controll pannel would send command to gsm to ring, thanks for your help aKG, cctv.

Tarsil

I've seen a circuit for that. It was using a PIC16F84 for sending a AT comand (ATDxxxxxxxxxx for calling a number stored in PIC's memory. U'l need a older Ericsson like GA628, A1018, T10. The number 1 pin at the charging/modem conector was put to +8V (Charging voltage for bat). No 3 pin was put to GND and no 2 pin was conected (trought a BC547) with pin 18 (or any other output) for the 16F84. Between pin 18 and BC547"s base was a 1 K res and also at Transistor's colector.
For extra info....google "ericsson at commands"

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cctv

Tarsil, could you give basic diagrame explaining your info, also what device linked to alarm pannel would give command for gsm phone to dial last dialed number, did not want pc connected if poss, i know of landline comunicator device that would dial numbers for landline phone but will not ring gsm, many thanks for info, cctv.

Tarsil

I'l post the diagram as soon i'l find the mag. The calling number is stored in the 16f84's memory. It dials it in the moment that a PIC's INPUT is set high, so u can atach to it all sort of devices.

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sho_gun

U may try a simple solution with a GSM phone with speed dial . U may connect a relay NO contact ( reed or other tipe ) actioned by the burglar alarm over the speed dial key previously set to ring u'r other gsm .

Madhouse

Quite right sho_gun, this is how I phone-enabled my motorbike alarm - I used a PIC chip to switch two small relays connected normally open over two number keys on an old un-cased Nokia 6210, and a third one over the "hangup" button. It would dial one number, wait 10 secs and then hang up and dial the other number. It would continue every five minutes to do this until the alarm was disarmed by the key fob.

Very simple to set up, and I was spoilt for choice as far as phones went!

Madhouse

The circuit diagram is attached. There is a fourth relay, which is able to power the phone on and off. The PIC chip is able to identify whether the phone is on and working by pressing the red "hangup" button, and then sensing whether the screen backlight has come on (mobile's LED power is connected to RA1 and was just enough to show a logic "1"). Obviously, if the LED power doesn't come on, the phone must be off so it can then power it on. This was only included because it was on a motorbike, and if not used for a few weeks the bike's battery can go flat. The PIC knows when the phone is not required, so can actually switch it off completely if needed.

Components aren't too critical, just don't forget the diodes! And, your phone needs power from somewhere.... I didn't include the 5v PSU for the PIC chip as these should be easy to do (Mine actually ran at the 4.6v off the PSU for the phone).

Your alarm input from a domestic burglar alarm may be the opposite polarity to the circuit shown so just change the software accordingly (this one is activated by 12v appearing on the alarm trigger input). I'd suggest taking this input from your bell box or siren output on the alarm panel, and just check to see whether its showing volts or grounded in its "sounding" state.

I used an old Nokia, timings for the software should work for most Nokia's including the newer ones. 6210's and 3210's are ideal and cheap though, just strip the guts out and solder the relay contacts straight to the keypad PCB and you are away.

The software I used was a lot more complicated and written in assembly, but I just whipped up (and tested) a simple BASIC program to show how it works; -


The whole program will continuously try to phone until such time that the alarm input is reset, there is no "give up after five calls" or anything like that. It is just to simply demonstrate the workings.

Taking the circuit further, you could perhaps use a 16 way analogue cross-point switch to control the keypad, which will give you enough keys to sent a decent text message as well....... or store a short encoded speech message (maybe a couple of seconds) in the program memory area of the PIC chip, and play that through a simple R2R ladder DAC to the MIC input of the phone ("Alarm! Alarm! Alarm!") over and over again during the 30 second dialing routine.

Hope this gives you some clues!

Attached Images

PIC GSM Alarm.gif (11.3 KB, 55 views)