NORB 2 A GREAT SUCCESS!!!
Yesterday was the first flight of our first ever to fly AVR based circuit board, and WOW did it perform well. A massive thanks goes out to every single tracker who helped us follow the progress of NORB 2 yesterday! You're all awesome!
Burst altitude = 36.1KM
After troubleshooting sound problems only minutes before launch, we were all set for launch of NORB's second flight. Armed with a GoPro HD Hero 3, NORB board version 3 (1 and 2 never flew because I kept making them better), and a backup pava in a ball named BRON, we were ready to take to the skies. And had it not been for Steve Randall assisting us hugely with the filling and launching and supplying of all the kit necessary for flight, we wouldn't have been going up. Thanks Steve!
And off she went, climbing at a steady 5 m/s attached to a Hwoyee 1200g balloon filled with hydrogen gas (we had 2 fire extinguishers on hand!) The pictures speak enough words themselves:
Above you can see BRON, our backup tracker, in the distance
Unfortunately, the GoPro didn't survive to shoot the landing, but this flight was still a huge success! After writing a quick Python script to turn the data on the NORB board into something useful, here was the result:
You can see from the above temperature graph that there's no way an exposed GoPro can survive -25 degrees celcius unless it's in its trusty case (and we thought it would overheat!) The graphs also show a very clear increase in humidity as the payload descended through the cloud layer and into the moisture of lower earth's atmosphere.
When NORB hit the ground, it was only 30ft from the A14! Struggling to find access to NORB's final location, I received a call from the famous Mr Upu. Having had Mr Upu's invaluable directions, we were able to find it much much sooner than we other wise would, if we'd have even found it at all! So thanks again Anthony! More pics to come...
So all in all, a very very very good, successful and extremely exciting day out! Now, what's the next project on my list? ;-)
The box is almost done! :D
After some careful designing and precision engineering in my Granddad's garage:
The NORB 2 box was born...
It's not quite finished, but only minor tasks have to be performed on this stunning piece of foam architecture if I do say so myself. We need to drill a small hole right through the centre of the box to allow coaxial cable for the 1/4 wave antenna to go from the NORB board SMA connector, to our antenna radials on the bottom of the box (still need to do that too). Then, we're just going to route some small cutouts to set the battery pack and NORB board neatly into the box so they can't move before glueing up the walls and bob's your uncle.
The foam has arrived and the batteries have saved me...
I'm delighted to announce that after running the camera non-stop on two fresh Lithium AA batteries, after 2 hours 30 minutes, 99% battery power remained. We are go for launch! Well, box design...
Yesterday evening just before I was due to go out, a nice sheet of 25mm thick blue styrofoam arrived:
I have started the designing of the box, and this time it really will be like a box. Our last payload was essentially a sandwich, with two pieces of foam being squished together to contain our vital components. This design should be more sturdy and hopefully a little more reliable. More on this to come.
In recent weeks, I have been tweaking the NORB board here and there to the point where I can now sit back and relax and get ready for a HAB flight hopefully next month. This week I made some slight changes to the code:
Since it's creation, the NORB board has been transmitting over the radio everything it can. By that I mean it has been transmitting temperature, voltage, humidity, as well as all the standard information you transmit as basic telemetry. By definition, a longer datastring coming down over the radio link has a higher probability of a decoding error.
To avoid this issue, I have taken the decision to record all our extra data such as humidity and voltage to the micro SD card, while transmitting only the basic telemetry along with a temperature field, and can now say that this is working good enough for flight.
NORB 3 Tracker is ready for flight!
In recent weeks, I have been tweaking the NORB board here and there to the point where I can now sit back and relax and get ready for a HAB flight hopefully next month.
What does NORB now do perfectly:
- The board sits quietly on my window ledge until it gets a GPS lock. As soon as it gets one, it processes it to check that its all valid data.
- Then, it takes some readings from the temperature/humidity sensor and reads the voltage across the cell from an analog pin on the microcontroller.
- It appends the new data onto the parsed GPS data and stores it as one string called the "datastring."
- The program then opens a file on the SD card and logs the latest "datastring" to a new line in the file.
- The datastring is split up into bytes, then bits, and is transmitted down over the 434MHz radio link back down to Earth where data can be decoded live using some software called dl-fldigi.
It has now come to the point where we need to start looking into camera options for our flight. Of course, there are a huge number of different ways of photographing or videoing HAB flight. I personally prefer taking HD video constantly throughout the whole flight to catch all the scenes of close encounters with aircraft and particularly the balloon burst.
The problem is, most cameras these days have maximum recording times due to tax reasons. In order to get around this, I needed some way of writing a script to record a video of x length, save it, and start another video of x length, in a loop throughout the flight - so I purchased this:
Yes it's a little bulky, has some weight to it and eats batteries like I eat chocolate. BUT, it's a Canon, and having a Canon allows the facility to use the CHDK, or Canon hacker's development kit.
After some fantastic help from Chris Stubbs, we managed to get a basic script working on the Canon doing exactly as mentioned above. It takes a 2 minute video, saves it, starts another 2 minute video, etc. Bingo, we've eliminated the problem of a max recording time!
Damn Power Issues...
Unfortunatley, my happiness was short lived. It took me less than 29 minutes to realise, my Canon on fresh batteries was only lasting 29 minutes. Of course, this was completely unacceptable for our HAB flight, so action needed to be taken.
At home, I have one of those portable charging hubs. This particular one has a capacity of 8400mAh and can apparently power devices for up to 24 hours fully charged. With this in mind, I had the idea to cut a USB cable apart to find the VCC and GND wires in order to solder them directly to the power terminals of the camera. The hub looks like this:
It's not the lighest of objects and offers a standard 5V output; not suitable to go straight into my Canon. It dawned on me that using this would force me to use an external regulator, but even then the ammount of extra weight I'd be carrying would be quite significant, along with all the uncertainties I'd have about it actually working for the full duration of the flight.
I soon dismissed the idea of using the hub and needed some other form of power... For HAB, I and many others opt for the Energizer Ultimate Lithium AA or AAA batteries. Unlike most alkaline batteries, these beauties have a much lower rate of voltage drop over time as can be seen on the graph below:
Now it says on Energizer's website that these batteries *can* last up to 9x longer than standard alkaline batteries in devices such as digital cameras, depending on the camera. So I took my 29 minutes on normal batteries and multiplied it by 7 to account for a slight safety factor which resulted in a rough estimate of 200 minutes or 3.3 hours!
This figure is more than enough for our flight which should last approximately 2 hours 30 minutes. Even still, it may be an idea to record slightly less often than constantly. This I would imagine may slightly increase the duration for our camera batteries. I've ordered 2 packs of Ultimate Lithium batteries.
Update: The batteries worked flawlessly and used only 1% power after 2 hours 30 minutes!
Then, we should be good to go. Our plan is:
Balloon: Hwoyee 1600g
Gas: H2 (Hydrogen Gas)
Absolute Max Total Weight: 1KG
Target Altitude: 37KM +
Launch site: Elsworth, Cambridge
Proposed launch data: Saturday 15th February