NSE1 High Altitude Balloon Launch

Posted on April 22, 2013 by Chris

The Launch

The morning started off a little frosty as we packed kit into the car and ran final tests on the payloads. NSE was performing normally but CHEAPO would not parse on Habitat. This was down to incorrect padding of the time (it was being sent at “64500” instead of “064500”). After a hotfix being applied to Habitat (Thanks DanielRichman) we were set up and ready for business.

The payloads were tied together and the balloon filled, before being released.

The balloon then climbed at an average of 4.3m/s to 27500m, before bursting and falling back to earth at an astonishing rate.

The Recovery

We drove to the landing site near Burwash and looked around as the balloon flew right above our heads on the tracker. I saw the faint shadow of the parachute on the horizon and headed across the town to the opposite side of the Forrest it was expected to land next to. After a few minutes of walking around with the radio we knew we were close. After speaking to one of the locals they let us climb over their fence to retrieve the payload from their field.

Post flight analysis

The balloon burst was predicted to be around 21000m so we were surprised and slightly worried as it carried on climbing all the way to 27000m. This was probably due to the balloon being slightly under filled as our average ascent rate was below target.

Cheapo’s GPS code worked fine. Maintaining a fix of 9 satellites throughout the flight. The only software bug being the padding on the time field, which has now been resolved so should not pose a problem on future flights. Cheapo only had a couple of receivers over its flight, who reported a very poor signal from it. I believe this was due to the radials of the 1/4 wave antenna being bent over the driven element. The next flight will use straws to prevent the radials from sagging or bending out of shape.

NSE’s signal was perfect, with about 20 simultaneous receivers at one point. The antenna reinforcing (straws) paid off and the payload could be heard from a fair distance away on landing. The path on the tracker appeared to jump to 0,0 at one point. Upon analyzing a data export from habitat that evening I found that the payload was having difficulty getting strings from the GPS module on several occasions, reporting back 0 connected satellites and falling back to the last know coordinates. This was most likely down to using Software Serial.

Temperature data was collected using the AtMega168’s internal sensor. The payload got down to -20C on its descent with no problems

The TK102 tracker we flew as backup did work in the end, however was probably not worth its weight as the firmware on it is horrible and proves very unreliable.

Overall the flight was a success, and I am very happy we managed to recover it okay. We are hoping to fly again with a better camera soon, and also try and fly CHEAPO on its own, either as a floater or with a pico balloon.

NSE gets twitter

Posted on March 24, 2013 by Chris

I have created @NSEballoon to post HAB related updates and keep in contact with other enthusiasts.

NSE1 Launch Planning (April 2013)

Posted on March 13, 2013 by Chris

I have heard back from the CAA that the preliminary approval will be issued tomorrow, which is fantastic news! The proper permission should be issued closer to our launch window in April (every weekend, in the hope that one will be good to launch in).

In the meantime I have been working on a SMD tracker board that, if finished in time, will fly as backup on the same flight. The objective of the tracker is to make a board for domlins pico flights as cheap as possible. Hence the payload name $$CHEAPO.

NSE1’s flight code has been adjusted to enable flight mode as soon as it gets a GPS fix. This is because the uBlox chip seems to get a fix much faster if left in default mode. Once the fix has been acquired it sends the command to switch to airborne flight mode.

NSE1 outputs telemetry strings on 434.650(ish)MHz at 50 baud, 7 bit ascii, 2 stop bits and 350Hz carrier shift. The format is as follows:

$$NSE,message_ID,time,lng,lat,altitude,satelites,battery,flight_mode,temp_internal*99A6

Self Etched SMD PCB (ATMega168PA Breakout) and programming

Posted on February 24, 2013 by Chris

With tracker v2 complete and ready to fly. I decided to start work on v3 and I really wanted to try out a SMD board, properly etched in a PCB house.

PCB etching is super affordable now thanks to Hackvana. You can get some great quality boards for well under £20. But while I’m just messing about testing connections and code I thought i could put together a little breakout board. This will also help me practice my EAGLE skills and make sure I don’t miss any vital components on the final design.

I went for an interesting take on the tried and tested toner transfer method. This time I printed my design onto a sheet of paper lined with Kapton tape. The results were pretty good with outstanding toner density in the middle, but needed touching up a little around the edges.

In this tracker I will be using the RFM22B board from UPU’s store. It is an interesting transmitter working in the 430mhz range with an output of up to 100mw. The frequency can also be set in software which is a handy feature to avoid interference etc. The module communicates with the arduino over SPI.

I am also planning to solder a Ublox 6 chip and SMD antenna straight to the final board.

Its worth noting that this board is entirely 3.3v to work with the Ublox and RFM22B.

Turns out i missed the smoothing cap from the output of the 3v3 regulator and the 10k pullup on the reset pin. Glad this was only a practice board as they could be bug-soldered on.

All soldered up with my great new iron. Fantastic price from the site recommended by Hix.

Programming the ATMega168p was a bit of a pain. But here’s how i did it in the end:

The chip was initially programmed with the arduino bootloader using another arduino as an ISP programmer. To do this you need to ensure the chips signature matches what the arduino IDE is expecting. I ended up modifying the boards.txt entry for the pro mini 3.3v as it was the closest match to my setup. I simply appended a P onto the end of the MCU name.

Once the bootloader was is programmed you can then program the chip over TTL/serial using the arduino IDE’s upload button. However i found that the chips signature had changed and i needed to remove the P i added to boards.txt earlier.

Device signature can be checked with:

C:\WinAVR-20100110\bin\avrdude.exe -p Atmega168p -c avrisp -P com8 -b 19200

NSE1 – Tracker v0.2

Posted on January 21, 2013 by Chris

This is the second version of my Ublox6 NTX2 ATMega328 tracker.

It is built around the TinyGPS library and reports back its GPS Time, Coordinates, Battery voltage and Temperature over a 434.65Mhz RTTY radio link.

Tracker Specification:
Chip: Atmel ATMega328P-PU
Chip bootloader: Arduino
PCB Design: ExpressPCB
PCB Etching: Toner Transfer
Voltage Measurement: Voltage divider and 1.1v internal analog reference
5V Regulator: TS2950CT low drop out regulator
Transmission mode: RTTY, 50 Baud, 425mhz shift, 7-bit ASCII, no parity with 2 stop bits on 434.650MHZ
Antenna: 1/4 wave with 4 radials
Battery: 4x Energizer Lithium AA cells
Radio Module: Radiometrix NTX2 (From HabSupplies)
GPS Module: Ublox 6 (From HabSupplies)

NSE1 – High Altitude Balloon

Posted on January 21, 2013 by Chris

This has been on the back burner for years. Those that do not know much about high altitude ballooning I suggest you check out http://ukhas.org .

NSE1 is currently in development and will contain:
GPS/RTTY tracker – Sends GPS location over a radio signal.
GPS/GSM tracker – Sends GPS location over SMS as a backup.
808 camera – Cheap mini camera to record the flight
Energizer Lithium AA Batteries – Work well at low temperature and are very light.
Foam payload box – keeps everything insulated and together.

Photos can be seen on Flickr

Chris Stubbs

A Blog about an electronic engineer with a passion for DIY hackery

Category Archives: NSE1