Trying to create an alarm without power.

[Salcritch]

Hi everyone, We are trying to build an alarm for our small holding which has been robbed 3 times. We have no main power so are tying to run off batteries/ car battery.
So far we have found a battery powere device witha sim which can call a phone. We are struggling to find a tremor detector which we can use on the gate when it opens and then connect up with the phone dialler.
Apologies if this isn't right for the forum but as amateurs we are struggling and thought there would be some great expertise here.

Thank you

[willbanks]

i would highly recommend to hire someone to install mains power in your home. i dont have to much knowledge on the subject but something that would be a lot simpler would be to have the gate opening trigger a loud alarm to scare them off.
do you live in a neighborhood?

[Ian.M]

*MOST* alarm systems run on 12V power and are usually designed to run from a SLA backup battery if mains power is interrupted.   Replace the main panel or control unit's backup battery with an external 12V deep cycle lead acid (leisure) battery with enough capacity for at least a week's operation in a tamper-proof battery box, add enough solar panel area to keep the battery charged in the month with the least insolation + a charge controller so it doesn't overcharge and fake out the mains power detection circuit^* so the alarm panel doesn't complain about mains failure and you'll have a fully functional alarm system that can use any sensors, sounders and accessories that don't require their own separate mains supply.  Many systems can either have their own GSM dialer board fitted or can power and trigger an external third party GSM dialer.

Don't buy any systems or accessories that don't either come with or have a publicly available installers manual complete with the default system codes if applicable - the security alarm industry can be a bit of an old boys club (not as bad as the HVAC industry) and  some manufacturers can be rather unhelpful to DIYers.

* that's where you need someone with enough electronics knowledge and test equipment to determine if its just a matter of tying the MCU's sensing input to a logic level or whether it needs to be fed a regular mains frequency pulse + build a micropower circuit to fake it.

[NivagSwerdna]

We are struggling to find a tremor detector which we can use on the gate when it opens and then connect up with the phone dialler.

Normally doors use Magnetic Switches i.e. a reed switch on the wired side and a magnet on the other.  (You could have a solid state equivalent with a hall effect sensor), or for vibration I have used a VIPER shock sensor (just google VIPER shock). 
As Ian M points out most alarm systems use 12V so the VIPER would be happy with that, and obviously the reed sensor would be happy with a large voltage range.
RS stock door switches e.g. http://uk.rs-online.com/web/p/security-alarm-door-window-switches/1220715/  They come in surface and mount in the door flavours.
Sounds like you need covert video too.

[babysitter]

Get a co2 bottle, a air horn and a normally-open valve. Power interruption causes noise.