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I am new to Arduino and want to create a graduation project for my university. I am thinking to create a GPS tracker that can be attached to a cloth to track kids, for example. So the requirements for this project is as follows: - The device should be small - It should upload its location to a web server constantly. - the device should work with battery for at least 8 hours

Now what components are needed for this project? What concern me a lot is that how can I find battery last this much time, if I need bigger battery, it may hinder the device from being attached easily.

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    There's a device you can buy off the shelf that can do all this already: it's called a mobile phone. The kids most probably already have one. – Majenko♦ Oct 15 '15 at 19:03
  • An arduino is a bad choice for this project, as it will lock you into using a larger, more expensive "hacker friendly" form of the GPS and data uplink (GSM or whatever) functions than would be used by an existing all-in-one solution. – Chris Stratton Oct 16 '15 at 2:16
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    It sounds like he is supposed to make the project, not buy a phone off the shelf. – Nick Gammon♦ Oct 16 '15 at 4:43
  • Apparently OP want the device to be small & mobile phone nowdays is 5/6 inch – Aircraft Oct 16 '15 at 9:20
  • Guys as Nick said I need to make the project for learning not buy a complete solution, I don't need to track my kids I just gave you an example – Abdullah Oct 16 '15 at 9:26
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In addition to @Majenko's post, you will save considerable power by turning the GPS & GSM off when not needed - for example, you might decide that once per minute, or once per 5 minutes is enough (maybe send it a text to trigger "continuous mode"?). Once the Arduino has switched off the other devices, it can go into "sleep" mode for a while. Check out Nick Gammon's excellent treatise on power saving modes at http://www.gammon.com.au/power

You can save both power and size by replacing an entire Arduino with an ATTiny - prototype on an Arduino first, then once it's working, move to an AtTiny - they have fewer pins, less memory, and are cheaper & smaller.

I doubt you could get the size smaller than a small cellphone, which can be had for very little - $35ish plus shipping, from http://www.aliexpress.com/item/Cheap-original-Mobile-phone-LG-Optimus-One-P500-WIFI-GPS-JAVA-Android-OS-Unlocked-Mobile-Phone/32274282341.html?spm=2114.01020208.3.1.zgFwLV&ws_ab_test=searchweb201556_1,searchweb201527_3_71_72_73_74_75,searchweb201560_9

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  • GPS takes a potentially significant time to regain satellits depending on how long it is off and where satelllites are. Maintaining an emphemeris or even producing an active one would help minimise acquistion time. – Russell McMahon Oct 16 '15 at 14:55
  • Generally, GPS' store their ephemerides, and/or they can be downloaded from the GPS. You may wish to test this - get a lock, power everything down, then power everything up, and time how long it takes to get a positive location. Ephemerides are valid for an hour, and GPS' come in and go out of view. Nevertheless, you will still use less power waiting for the download than you would leaving it on. If you are only polling once an hour, it may be worth polling every 55 minutes instead. – AMADANON Inc. Oct 17 '15 at 9:09
  • Ephemerides don't take longer to expire if you keep using them, you just get a new download before the old one has gone - this takes the same time as it would to get one after it has expired. – AMADANON Inc. Oct 17 '15 at 9:13
  • Further research shows ephemerides are valid for 4-6 hours, and are updated every 2 hours. Same applies - If you get a lock every hour-and-one-second, and shut down in between, you should need to download ephemerides at the 6 hour 6 second mark; if you get a lock every 59:59 minutes, you will need to download new ephemerides at 6:59:53. This may vary due to different satelites being visible, and from receiver to receiver. – AMADANON Inc. Oct 17 '15 at 9:23
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You have two options. Option 1. Buy a ready made pet tracking device from online market e.g (https://www.aliexpress.com/item/Pets-Smart-Mini-GPS-Tracker-Anti-Lost-Waterproof-Bluetooth-Tracer-For-Pet-Dog-Cat-Keys-Wallet/32887784462.html?spm=2114.search0104.3.1.26793604pFMLma&ws_ab_test=searchweb0_0,searchweb201602_3_10065_10068_319_10059_10884_317_10887_10696_321_322_10084_453_10083_454_10103_10618_10307_537_536,searchweb201603_52,ppcSwitch_0&algo_expid=09c58262-a0e7-4205-8fba-cd8265c15b3e-0&algo_pvid=09c58262-a0e7-4205-8fba-cd8265c15b3e). Then you can download the app and start tracking movement.

Option 2: The other alternative is to build one from scratch by purchasing all the necessary components. This is option is most appropriate for students. You can check this page for more https://electronicsforu.com/electronics-projects/hardware-diy/gsm-gps-based-vehicle-tracking-system. However, you may not be able to achieve the small size as you wanted but you should have something close to it if you carefully select your components.

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You need four things:

  • A GPS receiver
  • A GSM modem
  • An Arduino
  • A Battery

Using off the shelf products you would probably end up with something about the size of a cigarette packet at best - probably bigger.

To make it small enough to be unobtrusive would take a lot of work. You would need to design your own circuitry combining everything that is contained in the three circuits above into the smallest design you can, and since most existing solutions use pre-built modules (cans) that are relatively large you would first have to discover how they work and replicate them as one single tiny module.

And then there is the battery. GPS receivers are very sensitive devices. They have quite powerful preamplifiers to detect the incredibly faint signals of the satellites. Consequently they use quite a bit of power. Similarly GSM modems are quite power hungry, especially when they are far from a cell tower.

Put those together and you have quite large power requirements - so the battery will consequently be relatively large. Many times the size of the circuit you designed above.

So if you're trying to make something that James Bond might stick on the back of someone's jumper without them noticing you're very much out of luck I'm afraid.

That is why most tracking of people is done using a larger device that most people have sat in their pocket already: a mobile phone. You can already get software for most phones that will allow you to track your children.

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