School Project. Need Help!

Hello,

I was recommended to Arduino for a project I am working on for school. I am wondering if there is a way to have a device that is a good distance away (500 feet or more) send a message to a cell phone or an app on a phone. The device would sit horizontally and then would send a message once it was in vertical position. The message would have to be relayed to the phone or app within 5-10 seconds of the device becoming vertical. The size of the device would have to be relatively small and run on a AA battery and be able to withstand winter conditions. The main question is whether there is a device that is capable of relaying that type of signal once the device is vertical to a phone and how much a system like that would cost. This device would be used to signal when a tip-up flag was up and relay a message to a cell phone App. Looking for any type of help I can get in the most cost effective way. Thanks!

You have several sub-problems that you need to investigate.

1) The main problem is signalling a cell phone at 500 feet (150m). The normal method that could be used to connect Arduinos to cell phones is bluetooth, and that does not have the range. There are consumer radio devices that can get up to that range in optimal conditions like OpenSourceRF (http://www.opensourcerf.com/), but you would then likely need a second device that attaches to the cell phone that can say when the signal occurs. If you can put repeaters between the Arduino and cell phone, you could use things like IEEE 802.15.4 or Wifi signals to send the message (IEEE 802.15.4 would need a device that attaches to the cell phone, if the phone has wifi support, you might not need an attachment to the cell phone). Finally, your main hope would probably use a cell phone connection on the Arduino. You can get GSM shields that plug into Arduinos that use a SIM card from a GSM cell phone and allow it to communicate. In the USA, only a few providers use GSM. Obviously, you would need to factor in the cost of a cell phone connection. I imagine those pre-paid phones would be the best way for a limited project.

2) You mentioned winter conditions, but you did not mention how long the Arduino has to run in winter conditions. You would need to build/buy an enclosure for the Arduino/battery. There are a lot of choices out there, but be sure when you buy it there is room in the enclosure to house both the Arduino and battery (I recently bought one that was a little too narrow inside for some of the gear I wanted to put in it).

3) In terms of the winter, note, that ALL batteries have reduced power capacity in cold weather, so it likely means you need to plan for more batteries to provide the power. If you are planning to run on a single AA battery, you would need to boost the current up to what the Arduino can handle (3.3v or 5v, depending on the model), and I suspect your runtime would be measured in minutes in cold weather. A single rechargeable AA battery provies 1.2 volts, while the non-rechargeable alkaline battery provides a nominal voltage of 1.5 volts (though the alkaline voltage dips as the power is discharged).

4) In terms of cost, if you are just starting out, and don't have an electronics kit, you will need to budget for things like wires, breadboards, soldering irons, etc. If you have a lab at school or a maker space, you might be able to use their facilities.

Frankly, the simplest way to solve the problem is get an Android smartphone, and write an Android app that does the sensing, and sends a text message when the event occurs (http://developer.android.com/index.html). You might be able to use an iphone as well, but I don't know how easy it is to program an iphone if you haven't paid for a developer contract.

There are also several methods of sending serial through the audio jack on a cell-phone. This opens up your possibilities for radio (or even IR) communications tremendously. The disadvantage is that it requires a receiver on the phone side instead of using the phone's own electronics directly. And there are already apps that handle this type of communication and are configurable.

Text messages are likely to take more than 10 seconds to receive.

If you're within cell phone coverage you could use a cellular modem to send a text message - you might struggle to meet the 10-15 second target though.

If you use a cellular modem with data capability you could send your notification via the Internet, which would be much quicker but would require some sort of application or service on the receiving side. This would be easy enough if you are capable of developing networked apps on your handset, but rather difficult otherwise.

If you are able to use an intermediate device as a relay, you could establish a direct local connection. Openmicros sell a range of Arduino clones that include XRF radio transceivers that have quite a good range. I don't know whether they'd cover 500 feet in your environment, but apparently ranges of over 2Km have been achieved by using directional yagi antennae so perhaps you could get them to work. If you can, then you could use this to receive a signal from your remote sensor, and then some sort of network or serial adapter to connect locally to your handset. I don't know what options you have there but I guess you probably have cellular data or bluetooth available.