Beacon or GPS alarm? Help with idea

Hey Everyone.

I was thinking over the weekend and came up with an idea and I need your help to see if it would work or not.

I want to build a small project box that would hold a beacon or GPS alarm in it.

What I want to do is have a wire that would be a closed loop and the circuit would be off. If the wire is broken, then it would be open and that would turn on a beacon or GPS device that would send a signal to a cell phone and notify the user that the circuit is open. It would be powered by 2 AA batteries and use solar charging since I would need this to be out doors.

Any help? More questions I could answer?

Thanks everyone.


Have you considered that just about anything AFAIK that would be able to detect and charge a circuit on an open of another circuit is gonna use/waste more power than it is worth?

Might think about using a N.C. micro-switch (leaf switch). with the switch in the open position (with the leaf pressed) no power is wasted. when triggered by releasing tension on the leaf, you power up your gps and xmitter.

Detecting whether a circuit is open/closed, doesn’t have to cost much power. You could program the controller to sleep, wake up every few seconds, check the circuit and return to sleep mode again if nothing happened. When the batteries are solar charged as well, you probably could run it continuously.

Check Nick Gammons page on Power saving techniques.

Your GPS and GSM modules will use a lot more power though and will drain the batteries very soon.
Using just AA-batteries, there’s a high chance they can’t store enough energy to survive a few rainy days, if you power those modules continuously.

But perhaps it’s possible to power those only after you detected the circuit’s broken using transistors/mosfets.

I like the sleep idea…

I need it to notify me either SMS Text or email or something when the line is broken. Almost something like a trip wire?

It will be outdoors and no WiFi around so I would need GPS or Cellular correct??

What other battery options would I have?

Thanks for the help everyone…


GPS = Global Positioning System. If you want to know where your device is, then this is the correct technology to use.

GPRS = several different translations. One of the services provided by the modern cellphone network that allows your device to communicate over the internet is called GPRS. If you need to ask where your device is, then this is the correct technology to use. It can also be used to send email or rapid data updates.

SMS = Short Message Service. This allows your device to send out a short (160-char) message to another cellphone or possibly to an email gateway. If your device needs to send a short message infrequently (like less than one per minute) then this is the correct technology to use.

SMS is probably the best technology for this proposed device. The power consumption of the cellular shield is significant - it's probably best to work out some way to switch it on, wait 20 seconds for it to connect, then send the message and power down.

C's, Ds, More AA's, Sealed Led Acid, LiPo variants, caustic power packs (like polaroid used to use in their film packs. Good current, great shelf life).

My idea with the leaf switches was to only power up the electronics when triggered, so AA's would probably work, for a while (don't know what the power curve is like on GSM modules, but suspect fairly high).

Depends on what you want to do, if you want to track your project over great distances, you probably need cellular and GPS.

But you can use other ways of wireless communication as well. You can buy transceivers with a range up to 1/2mile quite cheap. Using 2 arduinos + transceivers, you could equip 1 set with the trip-wire and another one at home, sending emails/ flashing lights, sounding alarms etc., once the first detects something.

I think the SMS will be the way to go. I only it it to send a short message once. Then I can go and reset it and ready to use again.

So could you guys help me with a bit of a good parts list for this? If I use SMS do I need to setup some type of account with a cellular provider or anything?



iBeacon Scan/GPS (Bluetooth 4.0 Low Energy)

I think Morgan was correct: the op used the wrong term for GMRS/GPRS.

OP (Dez), Are you interested in Location as well as comm? Or do you just want to send a message that the remote has been triggered, and if so, how far?

@123Splat, i thought the caustic material in Polaroid films was to develop the film, not power the camera. Was I wrong?

I think Morgan was correct: the op used the wrong term for GMRS/GPRS.

OP (Dez), Are you interested in Location as well as comm? Or do you just want to send a message that the remote has been triggered, and if so, how far?

You are right. I just want to send a message that the remote has been triggered. It can shut off after the message was sent. It can also be off until it is triggered as well. This way I figured it would not use any power until it was triggered.


Thanks again everyone for all your help :slight_smile:


Well, start with a cellular (GSM) shield like this one from Sparkfun. You will need to buy a SIM card from a phone company to make it work, although you can just pop the SIM out of your own phone and put it in for testing. Depending on location, one company will have better coverage than the others. Depending on their payment plans, one company probably has a better deal for sending only a few SMS messages per month.

Once you’ve got it working on the bench, then you need to delve into the power consumption and battery-life issues. That particular Sparkfun shield might turn out to be a poor choice, due to all the other capabilities it has which you’re not using and don’t want to spend power (or dollars) on.

I only recently bought my first smart phone and have little knowledge about the subject. One thing I'm wondering about is using the cheapest phone you can find and hack it, to get extra functions.

It shouldn't be to hard to solder a few wires and program an arduino to "push" buttons on a phone using optocouplers (it may even be possible without). That would already give you the possibility to dial a number and send a message.
Using a Mosfet, you could turn the phone on/off completely as you please as well.

The arduino itself could be powered by the battery of the phone. You probably can't use the built in charging-circuit of your phone and will need an external circuit.

It will be one way communication only as well, but why spend a lot of money on an expensive shield, if that's all you need....

@123Splat, i thought the caustic material in Polaroid films was to develop the film, not power the camera. Was I wrong?

The SX70 & Suns (maybe wrong model, but the ones with powered film pack) film packs contained a 5V Battery pack under the film stack to supply power to the film drive. They made great supplies for 555's driving LEDs (used for remote beacons to get the boat back to the right cove after dark). You are correct about the developer being caustic, but it was in a paper packet attached to the end of each film sheet. Polaroid issued a warning about the battery pack contents being caustic.

Dez, Sorry about the sidetrack.

$69 is an expensive shield and a cheap phone can be obtained for less than this but the effort in hacking the buttons has an expense. Hacking it in a way that it lasts longer than a month before a wire falls off is even more expensive. If you’ve got lots of free time then go ahead. I would buy the shield if I needed this SMS messaging function.

No problem at all guys :slight_smile:

The only crappy thing I am finding right now with using SMS messaging is that I need a phone company and pay as you go with the SIM card. This may only go off a couple times a month.

Maybe there is a simpler way to doing this?

Tell us more about your project, you told you want an E-mail, SMS or... something that notifies you.

As signal you could wave a flag or set stack of hay on fire :slight_smile: , but the better you tell how it should function, where you'll locate it, what is and what isn't possible, the easier it is to look for answers.

It's located outdoors and if it's too far away from a cheap internet connection, you probably need a GSM-shield/phone.

Far is quite relative though, as told you can use other RF-techniques as well and if half a mile isn't enough, you could also use several arduinos + RF-modules as repeaters, for example.

Basically want I need to do is setup a small box. Have a trip wire on it. If something trips the wire and breaks the connection, I would like to be notified somehow. This is going to be in the wilderness outdoors. Sometimes near creeks, sometimes in the middle of the woods.

Somehow I need to have it send me a text or maybe start a beacon or something so I know it has been tripped and I need to go to it.

Hope this helps.