GPS TX RX Project intro

I’ve started a project to build a tracker and receiver unit for Duke of Edinburgh, or other expedition, groups – all using Arduino!

Why you ask, WHY!?!

Well indeed. There are trackers on the market that you can buy for approx £100, or rent for approx £30 per weekend, but they are limited.

For starters, they are all Mobile Phone SMS based. What’s the point of this in the backside of Scotland!?! No phone reception there, plus you pay per message.

Secondly, I hate paying for things which would be dirt cheap if profiteering gluttens weren’t in charge of them.

And thirdly, I’m learning Arduino and absolutely hate ‘hello world’ programmes!!! I wanted to do something real, and useful.

What will it do?

I started to think – all D of E groups must have fairly local supervisors – ones in the wilds have a Mountain Leader performing remote supervision. This means you don’t need a massive range.

So I figured a cheap pair of radio boards, a GPS board, an Arduino computer, a battery and a housing would get me a good way to transmit.

On the receiver side, the radio, arduino, shell, battery and a 16×2 LCD display would enable me to show the paired radio’s location as WGS84 lat/lon or UK Ordnance Survey Grid Refs.

As it happens, I’m a map geek – so have the grid ref conversion code already in a range of languages!

The kit

I had a look around for a radio system and found that some people had doctored off the shelf 433 MHz public use spectrum radios to get a max range of 30km!

All I really need is probably up to 10km at a push – so this is a good place to start.

I went online and found that the UAS helicopter brigade’s ardupilot was used often with the 3DR Robotics 433MHz radios. These have a tonne of information available to help you get to use them with Arduino. Not a bad place to start – later on if we need to we can always switch out the tx/rx for another system.

The UBlox GPS chip is also often used for autopilot systems with ardupilot. Again lots of code samples, so I picked up a cheap clone that works nicely.

Just had my birthday recently – which means Birthday Money! I headed over to Sparkfun to spend my dosh.

Picked up some nice pieces. Found a project box that looked good. Also some very small (and funky red) breadboards for prototyping.

Picked up a couple of Sparkfun’s Arduino Pro Mini clones too, and a serial to USB FTDI programming board. Idea being plug in, programme, and detach. Better than having it on board for my needs.

Also found a groovy 16×2 LCD display, black on green, with adjustable contrast. Although now I have it, it looks huge compared to the rest of my project!

As you can see from the below, it’s shaping up nicely.

gpxtxrx-bits

The wired on the breadboard are just the 3.3V VCC in and the GND lines. I’ve wired up the far right vertical line as a GND on the top and bottom of the breadboard. Next to it is the 3.3V VCC line.

Top right shows a 90 degree pair of pins for connecting a power supply.

The setup gives me enough pins to power all the external 3.3V pieces, with a couple of pins spare!

There’s no battery recharge circuit in there – I’ll have them disconnect the battery for that. May be a good add on in V2 so people don’t have to open the box to charge.

Why not have it pre-fabbed?

The idea is not only to create something useful – but also something my teenage air cadets can build themselves.

If you think about it this is a great data-comms project. I’m going to make most things configurable on the board in a single line of code in Arduino.

This means they could experiment with different transmitter power levels, LCD brightness, pro mini clock speeds for battery life, frequency of location reports, and even different antennae types and range.

What’s next?

I’ve already proved I can integrate the GPS and compass, and use the radios on 3.3V.

Next step is to repeat that trick using the core arduino libraries, and software serial to drive the Ublox GPS.

I also have to figure out the LCD – I’ll use this as a debugging tool so I can see what’s going on in the board later on.

Watch this space!

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