Pi In The Sky Telemetry Board Released

High Altitude Ballooning is an increasingly popular hobby (I nearly said that interest has been “ballooning”, but fortunately I stopped myself just in time …), bringing what is termed “near space” within the reach of pretty much anyone who is willing to put in the effort and spend a moderate amount of money.


Although it’s possible to successfully fly and retrieve a balloon with a simple GSM/GPS tracker, the chances are that this will end in failure and tears.  GSM coverage in the UK is nowhere near 100% especially in rural areas which is where we want (and aim) the flights to land.  The next step up, in reliability and price, is a “Spot” tracker which works solely via satellites, but those don’t work if they land upside down.  Also, neither of these solutions will tell you how high the flight got, or record any science data (e.g. temperature, pressure), or indeed tell you anything about the flight until they land.  If you’re lucky.  A lost flight is a sad thing indeed.


For some countries (e.g. USA, but not the UK), if you are a licensed amateur radio operator you can fly an APRS tracker, in which case the flight will be tracked for you via the ground-based APRS network run by other radio hams.  Sadly UK laws prohibit radio hams transmitting from an airborne vehicle, so APRS is out for us.

For these reasons, pretty much everyone involved in the hobby in the UK, and many other countries, uses radio trackers operating in an ISM (Industrial. Scientific and Medical) band where airborne usage is allowed.  These work throughout the flight, transmitting GPS co-ordinates plus temperature and anything else that you can add a sensor for.  Many radio trackers can also send down live images, meaning that you can see what your flight is seeing without having to wait for it to land.  Here’s a diagram showing how telemetry from the flight ends up as a balloon icon on a Google map:


What’s not shown here is that, provided you tell them, the other balloonists will help track for you.  So not only will you be receiving telemetry and images directly via your own radio receiver, but others will do to.  All received data is collated on a server so if you do lose contact with the flight briefly then it doesn’t matter.  However, this does not mean you can leave the tracking up to others!  You’ll need to receive at the launch site (you have to make sure it’s working!) and also in the chase car once it lands.  The expense of doing this is small – a TV dongle for £12 or so will do it, with a £15 aerial and a laptop, ideally with a 3G dongle or tethered to a phone.

Traditionally, balloonists build their own radio trackers, and for anyone with the skills or the time and ability to learn programming and some digital electronics, this is definitely the most rewarding route to take.  Imagine receiving pictures of the Earth from 30km up, using a piece of kit that you designed and built and programmed!  So if you are up to this challenge (and I suspect that most people reading are) then I recommend that you do just that.  It takes a while, but during the development you’ll have plenty of time to research other aspects of the hobby (how to predict the flight path, and obtain permission, and fill the balloon, etc.).  And when you’re done, you can hold in your hand something that is all your own work and has, to all intents and purposes, been to space.


For some though, it’s just not practical to develop a new tracker.  Or you might be a programming whizz, but not know which end of a soldering iron to pick up.  It was with these people in mind that we (myself and Anthony Stirk – another high altitude balloonist) developed our “Pi In The Sky” telemetry board.  Our principle aim is to enable schools to launch balloon flights with radio trackers, without having to develop the hardware and software first.  It is also our hope that older children and students will write their own software or at least modify the provided (open source) software, perhaps connecting and writing code for extra sensors (the board has an i2c connection for add-ons).

The board and software are based on what I’ve been flying since my first “Pi In The Sky “flight over 2 years ago, so the technology has been very well proven (approximately 18 flights and no losses other than deliberate ones!).  So far the board itself has clocked up 5 successful flights, with the released open-source software on 3 of those.  Here’s the board mounted to a model B (though we very strongly recommend use of a model A):

pits (1)It comes in a kit complete with a GPS antenna, SMA pigtail (from which you can easily make your own radio aerial), stand-offs for a rigid mounting to the Pi board, and battery connectors.  Software is on https://github.com/piinthesky, with installation instructions at http://www.pi-in-the-sky.com/index.php?id=support, or there is a pre-built SD card image for the tragically lazy.  We do recommend manual installation as you’ll learn a lot.

By now you’re probably itching to buy a board and go fly it next weekend.  Please don’t.  Well, buy the board by all means, but from the moment you decide that this is the project for you, you should task yourself with finding out all you can about how to make your flight a safe success.  For a start, this means learning about applying for flight permission (which, if you want to launch from your garden at the end of an airport runway, isn’t going to be given).  Permission is provided together with a NOTAM (NOtice To AirMen) which tells said pilots what/where/when your launch will be, so they can take a different path.  You also need to learn about predicting the flight path so that it lands well away from towns or cities or motorways or airports.  I hope I don’t need to explain how important all of this is.


There’s lots more to learn about too, for example:

  • How to track the flight
  • How to fill a balloon
  • Where to buy the balloon
  • What size balloon?  What size parachute?  How to tie it all together?

None of this is complicated (it’s not, ahem “rocket science”), but there is a lot to know.  Don’t be surprised if the time between “I’ll do it!” and “Wow, I did it!” is measured in months.  Several of them.  In fact, worry if it’s less than that – this research takes time.  We will be producing some teaching materials, but meantime please see the following links:

As for the board, it provides a number of features borne out of a large number of successful flights:

  • Efficient built-in power regulator providing run time of over 20 hours from 4 AA cells (using a model A Pi)
  • Highly sensitive UBlox GPS receiver approved for altitudes up to 50km
  • Temperature compensated, license-free (Europe) frequency agile, 434MHz radio transmitter
  • Temperature sensor
  • Battery voltage monitoring
  • Sockets for external i2c devices, analog input, external temperature sensor
  • Allows use of Raspbery Pi camera
  • Mounting holes and spacers for a solid connection to the Pi

The open-source software provides these features:

  • Radio telemetry with GPS and sensor data using UKHAS standard
  • Radio image download using SSDV standard
  • Multi-threaded to maximize use of the radio bandwidth
  • Variable image size according to altitude
  • Stores full-definition images as well as smaller transmitted images
  • Automatically chooses better images for download
  • Configurable via text file in the Windows-visible partition of the SD card
  • Supplied as github repository with instructions, or SD card image

Finally, anyone interested in high altitude ballooning, using our board or not, should come to the UKHAS Conference on 16th August 2014 at the University of Greenwich.  Anthony and I will be presenting our board during the morning sessions, and will run a workshop on the board in the afternoon.  For tickets click here.

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Pi In The Sky Project – Successful Test Flight

This was the third flight of the “Pi In The Sky” board, but the first flight of the new open-source software written specifically for it (previous flights used a modified version of my usual Pi tracker software). The new software is a single multi-threaded program (instead of a collection of separate programs) and is configured via a text file so that for most users no recompilation is needed.

For this flight I used a foam polystyrene egg bought from HobbyCraft. The Pi and tracker board fit neatly inside one half:


whilst the camera, GPS antenna and battery pack fit inside the other. No other packing was needed and the 2 halves were glued together with UHU Por polystyrene adhesive. Here’s the result:



The glue is strong, but just to make sure I put some tape around the egg to keep the halves together.  Here’s the resulting payload, as I start to inflate the balloon:



The launch was easy, and we watched for a while as the flight broke through the clouds and started to download some nice images, after which we set out to chase.  We were expecting the flight to land east of Ludlow, and we initially stopped near Leominster till the balloon turned west, then nearer Tenbury Wells as we waited for the burst.  That happened at 31644 metres, nearly 2km above the calculated figure, and pretty good for a 500g balloon.  Here’s the full flight path:


We were about 3 miles away when it landed, which isn’t bad considering the narrow winding roads in the area.  Landing spot was 4.5 miles from the prediction which is also pretty good.  Once it landed we headed for the last position, and when about half a mile away we received a signal strong enough to decode.  We then had the final position which was near a farmhouse:


We parked up and spoke to a farm worker and then the farmer who was very helpful, allowing us to wander round trying to find the payload.  Initially we went to the wrong place, having transcribed the co-ordinates wrongly!  So we went back to the car, got the correct position, and checked the view from the payload’s camera which the farmer recognized:


Once we had that information it only took a couple of minutes to locate the flight, which was on the ground with the line going over a bush.

So, a successful first flight for the new software and third flight for the new board.  There’ll be another test flight soon, hopefully next weekend.  Meanwhile, some photos from the flight:



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Pi In The Sky Board Pre-Sale


The first batch of boards are in production. We’ve had a lot of interest and have decided to open up the shop for orders. The board is supplied as a kit including:

  • Pi Tracker Board
  • Spacers and mounting screws
  • GPS Antenna
  • Radio Antenna
  • Battery cable

Order Now!

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Pi In The Sky Add-On Board

What you see below is a simple and reliable GPS radio tracker board for the Pi. Together with the supplied, open-source software it embodies the experience of about 40 successful flights, nearly half of which have used the Raspberry Pi.


It features:

  • Efficient built-in power regulator providing run time of over 20 hours from 4 AA cells
  • Highly sensitive UBlox GPS receiver approved for altitudes up to 50km
  • Temperature compensated, frequency agile, 434MHz radio transmitter
  • Temperature sensor
  • Battery voltage monitoring
  • Sockets for external i2c devices, analog input, external temperature sensor
  • Allows use of Raspbery Pi camera
  • Mounting holes and spacers for a solid connection to the Pi

The open-source software provides these features:

  • Radio telemetry with GPS and sensor data using UKHAS standard
  • Radio image download using SSDV standard
  • Multi-threaded to maximize use of the radio bandwidth
  • Variable image size according to altitude
  • Stores full-definition images as well as smaller transmitted images
  • Automatically chooses better images for download
  • Configurable via text file in the Windows-visible partition of the SD card
  • Supplied as github repository with instructions, or SD card image


Some prototype boards are in the hands of testers and have flown successfully twice now.  The first batch of production boards have been sent off for production now will be on sale mid-late July.  Meanwhile, follow @pitsproject for the latest information.


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St Alban’s School – Successful Flights

To much relief, Alban the school mascot was recovered from a tree in a field in Cheshire. See this write-up in the local Cambridge newspaper.


The “floater” flight initially did very well, ascending at the target rate (which is a challenge in itself with these flights), and turning west at the predicted latitude. It then achieved a float but only for a couple of hours, when the balloon burst resulting in a wet landing off the coast of Blackpool. During the flight many images were sent down over the radio link, so it was a good flight though the aim wasn’t achieved.

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St Alban’s Catholic School Launch

Weather permitting I’lll be doing 2 flights for St Alban’s Catholic School. Members of their Code Club will help with the launch and recovery, whilst others will man Mission Control at the school.

The first flight is a “floater”, expected launch time 11am, which is intended to fly west over Ireland. This will carry 2 trackers ALBANFLOAT and ATLANTIC, the former with live image downloads.

The second flight is a normal up-burst-down flight, expected launch timemidday, with 2 trackers ALBANVOYAGER and ALBANDATA, the first with live images and the second with a number of environmental sensors.

Go to the live map to watch the flights, and see the links for the images from the flights and video stream from the launch site and chase car.

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Camera Test Flight

This was a flight to test some cameras under the demanding conditions of near space.

First, I was sent a prototype of a 360-degree camera which is the subject of a KickStarter campaign.

I installed this plus a large external battery (to extend the run time) in a foam polystyrene ball:


I was also sent a pair of 1080 XD Mini cameras by ReplayXD. These are small and very neat action cameras that can record 1080 line HD video at 25fps, or 720 line at 50fps. We chose the former, and I fitted one camera looking outwards and one upwards to capture the balloon burst. I used my new modular payload system which makes it easy to mix and match different cameras and trackers without having to build a new payload box each time:


We used one large backup battery and one small one. Even the small battery was enough for the flight so the larger battery would not normally be needed for a balloon flight. Here’s everything including one of Anthony Stirk’s early radio tracker boards:


A third payload was added, with a second radio tracker, and we also added a small GSM tracker. It took several people to hold all the payloads when we launched:


and it made an impressive sight as it rose in the sky:


The flight landed in a field about 2 miles from the launch site, though it travelled a long way horizontally as well as vertically to get there! We arrived just in time to rescue it before the cameras were gobbled up by some farm machinery …


We were eager to get the cameras back home to have a look at the images, some of which are truly stunning. First, from the Centr camera:

Still 1

Still 2

Of course, those are just single camera still views from the 360-degree video; I’ll post links to the stitched footage when available.

Meanwhile both ReplayXD cameras were working well, with the outward-facing camera capturing this shot of the Centr camera shortly after burst!


Just before burst, the upward-facing camera got this great shot showing how translucent the balloon is when it’s about to burst:

and here’s the burst, all over in about 1/10th of a second:

Burst 1

Burst 2

Burst 3

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Car Tracker – Update

This is a follow-up to an earlier post where I made a car tracker from a Raspberry Pi, GPS and a small TFT display. Since then I have:

  • Replaced the GPS receiver with one using an external antenna
  • Replaced the display with one that’s easy to install in my chase car
  • Installed the system in my car
  • GPS Receiver

    The previous receiver found it difficult to get a GPS lock, because it was so close to the Raspberry Pi and of course did not have a clear view of the sky from the confines of a car. The new receiver has an SMA socket for connection of an external mag-mount type GPS receiver. This will work well inside a car, and in the case of cars with heat-feflective windscreens could be placed near the back of the car or even on the roof.

    The GPS module plugs straight into the GPIO header on the Pi, so installation is very simple.


    The device is made and sold by HAB Supplies


    There are many inexpensive monitors for sale now that are intended for use as car reversing displays. They run directly from the car 12V supply, and have 2 video inputs either of which can connect to the composite output on the Raspberry Pi. I bought one with a small stand to place in my chase car like so:



    I placed the Pi itself on top of the dash, using strong Velcro mounting tape. As this aimed the camera downwards I had to bend that up to being vertical, using a small heat gun to soften the plastic. Finally I connected the Pi to the display, and both to the car 12V supply (Pi via a USB power converter).


    So, now I have a small, low power car tracker that connects to the internet automatically via my MiFi device installed in the car. Switches on the side of the Pi control whether it uploads the car position, and whether it streams video from the camera. It all runs independently of my Windows-based car PC, and should hopefully run with fewer problems (and certainly using a lot less power!).

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    Heston, We Have A Potato

    This fun project started with a call from a TV production company who were working on a series for Heston Blumenthal. They’d heard that I fly the Raspberry Pi and wanted to include it in their Pie episode. The idea was to fly a potato as that was the first vegetable to be grown in space.

    Fast forward a few weeks, we had the challenge of finding a day that had good wind predictions and good weather, and would fit in with the filming schedule and Heston’s diary. Not easy, as you can imagine. However we did find such a day, with Heston available throughout, and I prepared a payload to fly. That needed to contain 3 GoPro cameras, including one looking down and one out sideways, plus a Raspberry Pi to send telemetry and live images from the flight:


    On top of this I placed some foam blocks to hold everything in place, then a further camera to record the balloon burst:


    On launch day, the first to arrive was Jon who’d made this wonderful retro-styled rocket, piloted by a King Edward with a familiar face:


    We worked together to mount his rocket to my payload, using a shaped piece of balsa wood fixed to the underside of each:


    With the main payload finished, plus a spare back tracker, we waited for everyone else to arrive. Julie served bacon butties to all. Heston was a bit late, and his bacon was sad and solid by then, but he still ate it :-). Here he is posing next to my BaCoN shirt :-)


    … and with Julie …


    After this it was time to go and launch. The film crew were very unobtrusive so I found it easy to just get on with the launch, chatting with Heston and explaining how it all works.


    There was little wind so the launch was easy. After feeding up the balloon and payload …


    … I just stood back to let Heston do that to camera:


    Next job of course was to chase the flight. The prediction had it going from Berkshire to Essex, so there would be little chance of getting there before it landed even without a film crew so slow things down!

    We saw some great images throughout the flight from the SSDV system, and had good telemetry also. Here’s an image (from a GoPro) during the flight:

    When we got to the area, some time after the flight landed, we got a very strong signal from near the road, and my direction-finder swung round rapidly as we passed the landing spot. Someone in one of the other chase cars saw it in a field as we passed! We then stopped to check maps and find the easiest way to get close to the payload. It was then a short drive to get to the field, where we donned wellies and made our way to the potato before it took root!


    Heston had gotten more and more attached to the potato during the day, and he genuinely seemed unwilling to mash the thing up by the time it was recovered!


    This was all back in October 2013, and the show didn’t go out until May 2014! If you missed it, watch for repeats on Channel 4 or 4Seven, or watch it on 4oD.


    Raspberry Pi Time Lapse

    Flight video from the show

    Heston talking about the flight on Chatty Man

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    Paper Plane, Battery Drain And Then Ukraine

    This was a pretty successful flight though it didn’t quite go to plan!

    It was a joint project with Anthony Stirk who has written it up here. The aim was to drop a paper plane over the North Sea, with that landing in Holland whilst the main payload continued on. Originally we were going to drop a second plane later on in the flight, but decided against that. The main payload (the one doing the dropping) was a Raspberry Pi with a Pi Camera, running via a switching regulator from 6 Lithium AA cells. It also had a small MOSFET board driving 3 resistive cutdowns – one for the first pane, one for the absent second plane, and one to drop the Pi itself to descend under a parachute. The Pi was programmed to trigger the cutdowns at longitudes of 4, 15 and 20, with the aim of having all 3 payloads landing inside our tracker network and thus potentially recoverable. The cutdown procedure started by switching the camera to video mode, then sending approx 8W into the cutdown resistor for a period of 8 seconds.

    The day started with Anthony cutting and folding his paper planes from a sheet of thick A2 paper in the statutory Fuchsia Pink. It was a neat design incorporating a little cockpit for the radio tracker:


    Meanwhile we figured out a way of mounting it on the main payload so it wouldn’t snag, then I set about putting that payload together.

    At the launch site, there was initially very little wind, but as soon as I needed to measure the neck lift the wind picked up and didn’t let go until after the launch! It took what seemed like ages to get any sort of accurate neck lift measurement, and that was a bit over target but not enough to prevent the balloon from floating. At this time of year, and particularly with the current winds, it’s nigh on impossible to have a HAB flight launch from and land in the UK, so a better option is to go for a “floater” where the balloon runs out of lift somewhere between 30 and 40km altitude, instead of going up till it bursts. For the size and make of balloon we were using (a 1600g Hwoyee), if you aim for an ascent rate of 4m/s or less then it’s going to float instead of burst. We aimed for 2m/s to make sure! Here’s the wind shortly before launch:


    We had to be patient, but eventually the wind dropped enough for a fairly straightforward launch. Back at the car I wasn’t getting any reception from CLOUDY (the main payload) but that was because I hadn’t got an aerial plugged into my receiver! Anthony’s SNOW (the plane) was working fine but his experimental backup tracker (WANNAB1), which was hanging just below the balloon, wasn’t being received. He suspects a shorted aerial.

    The flight path followed the prediction very closely, heading north-east before turning east over Bury St Edmunds. The ascent rate was pretty close to target too, just a bit over because of the overfill. We then helped Leo Bodnar with his 2 launches, before returning to my house to watch progress.

    Images from the Pi were reasonable, but because of the side-mounted plane the camera was pointing downward, meaning that none of the shots quite showed the horizon. Also, because of the late launch, it hit sunset earlier than planned. Nevertheless it returned some decent images including this one (fixed by Steve Smith G0TDJ for some missing packets)


    CLOUDY was programmed to drop SNOW over the North Sea, at a longitude of 4.0, and we watched with tense anticipation as that longitude was reached. To our great relief we soon saw SNOW descending, and it soon became clear that it was actually flying – the descent rate was near that expected for a parachute, and the GPS positions showed that it was repeatedly stalling and then flying again. Here’s the flight path showing the separation over the North Sea:


    and, thanks to Anthony, some Google Earth paths for the separation:


    The acceleration and deceleration of SNOW are clear to see on that second image.

    Meanwhile, CLOUDY continued onward and upwards. With the paper plane gone, the camera had a more horizontal view and by chance was pointing towards the setting sun, taking some great shots including this was with Venus clearly visible:


    CLOUDY then achieved the desired float, at about 34km:


    By then it was in the expected very strong winds, reaching speeds of up to 330kph (205mph), so it soon crossed the Netherlands and into Germany, touching the Czech Republic before entering Poland. By then it was further south than expected and heading South East instead of East, so we had fewer listeners in range than we’d hoped, but still coverage was pretty good.

    The second cutdown triggered at longitude of 15, as programmed, though of course there was no second plane to drop. However this is where things went wrong – the cold batteries couldn’t supply the cutdown current, and the Pi reset. Of course when it restarted, and regained GPS lock, the cutdown program hit the cutdown again (actually the first cutdown), and it rebooted again. At this point I knew the flight was doomed to a cycle of rebooting, so after a while of watching it do just that I switched off the PC to watch the telly.

    It might have been a clue when Mission Impossible came on. Once I got bored with that, I decided to quickly check the live map before retiring to bed, and was rather surprised to see that CLOUDY had managed to get past the boot-cutdown-reboot cycle. That cycle includes up to 3 cutdowns each time (2 for the planes and one for the Pi itself), and as the Pi was still floating it was clear that the final cutdown hadn’t managed to sever the line holding the Pi up. So although I was very pleased it had got so far, I knew that it wasn’t going to come down anytime soon and that the batteries (which would only last 20 hours even without the battering from the repeated cutdown cycles) would die soon. Which they did, with Pi approaching Kirovohrad in Ukraine:


    Most likely the flight continued at least till sunrise, and probably burst soon after that, landing in or near the Caspian Sea.

    So, an interesting flight, with some things learnt and things to do (some tests on very cold batteries and high currents, and a more reliable cutdown system for such flights).

    Thanks go to Anthony of course, Leo Bodnar for helping out, Phil Heron for providing the SSDV software, the CUSF guys for the tracker, Steve for the edited SSDV image, and everyone who tracked the flights for us.

    Footnote: CLOUDY was named after our cat Cloudy who has been missing for 6 weeks. It seems unlikely now that we’ll see him again, but a flicker of hope remains.


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