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home security system design

Former Member

I promise u I am not in the electronic security business.  I'm just a tech enthusiast & do-it-yourselfer.  As such, I had put together my own home security system yrs ago.  It's time to upgrade.  Mine has a telephone dialer/msg player that dials up several phone no.s and plays my pre-recorded msg to each, when the alarm is triggered.  I do not use a private monitoring co.  It calls me & police directly.

Seems 2 me that a big flaw in a home security system is dialing out over a land line whose wire can easily be cut, where it enters the house.

Where can I obtain a cellular base station unit (or how can I adapt a cell phone) to work with a recorded-msg-player and alarm center triggering  (my alarm center will trigger add on components by current signal or by relay contact closure).

Of course, why does anyone build it himself & skip the monitoring co., but 2 save $.  So, I don't want 2 pay 4 a cell phone no & contract just 4 a cell phone that will sit unused most (hopefully all) of the time.  I'd like 2 adapt one of those pay-only-for-the-calls-u-make phones if possible (? Jitterbug or whatnot).  I know that phones fron defunct contracts will still work to call 9-1-1, but I'd like it 2 call me also, so I can go 2 web site 4 my web cam.

FINALLY - THE QUESTION - do u know of such device avail 4 sale anywhere, OR do u want 2 design such a product to market 2 the various do-it-yourself home security alarm mfgrs (GE, X-10 Powerhouse, etc)

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    There are various ways to get "free" M2M communications over cellular. The tricky part is getting the cellular plan for a "calls only" service. I am not aware (in the USA) of any plan like you describe. All the pay-as-you-go plans expire (and release the phone number for reuse) if you don't add dollars/minutes every so often - usually every 30 to 90 days.

     

    From a hardware perspective, the simple hack way to do it is simply to drive the keyboard lines of a phone directly from your micro. I've done this in the past. Due to the way they're implemented, it is easiest to use relays for this task. Your life will be simplified if you can program your numbers into the phone's speed-dial memories so that you only need to "press" the 2 button for 2 seconds to dial the first number, and then END to end the call.

     

    SOME phones have a reasonably-documented serial protocol available on an external connector. This is annoying and hit-or-miss though.

     

    You can also buy a GSM module that can be controlled with AT commands - that way you only need a UART to talk to the module, and an audio path. This will not be as cheap as a $30 (or less) throwaway phone, however.

     

    One thing you might not have considered is to use an Internet-based service to do the dialing - use your broadband connection as the backup to the phone line. There's a long discussion we could have about the infrastructure options here. Personally I don't usually pick up voice calls of any sort - I use my phone as an email/web/SMS device - and I don't have a home phone line at all. So my preference for M2M notifications like you describe is email or SMS anyway.

     

    Oh, one other final point: Without going into details, I can assure you with absolute definitive finality (insert as many other strengthening words as you like here) that no alarm manufacturing company will buy your design. Their existing designs are already capable of working this way, but for business reasons are not implemented like this.

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  • 0

    There are various ways to get "free" M2M communications over cellular. The tricky part is getting the cellular plan for a "calls only" service. I am not aware (in the USA) of any plan like you describe. All the pay-as-you-go plans expire (and release the phone number for reuse) if you don't add dollars/minutes every so often - usually every 30 to 90 days.

     

    From a hardware perspective, the simple hack way to do it is simply to drive the keyboard lines of a phone directly from your micro. I've done this in the past. Due to the way they're implemented, it is easiest to use relays for this task. Your life will be simplified if you can program your numbers into the phone's speed-dial memories so that you only need to "press" the 2 button for 2 seconds to dial the first number, and then END to end the call.

     

    SOME phones have a reasonably-documented serial protocol available on an external connector. This is annoying and hit-or-miss though.

     

    You can also buy a GSM module that can be controlled with AT commands - that way you only need a UART to talk to the module, and an audio path. This will not be as cheap as a $30 (or less) throwaway phone, however.

     

    One thing you might not have considered is to use an Internet-based service to do the dialing - use your broadband connection as the backup to the phone line. There's a long discussion we could have about the infrastructure options here. Personally I don't usually pick up voice calls of any sort - I use my phone as an email/web/SMS device - and I don't have a home phone line at all. So my preference for M2M notifications like you describe is email or SMS anyway.

     

    Oh, one other final point: Without going into details, I can assure you with absolute definitive finality (insert as many other strengthening words as you like here) that no alarm manufacturing company will buy your design. Their existing designs are already capable of working this way, but for business reasons are not implemented like this.

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