2013

Posted on July 8, 2013 by Chris

After the disappointing signal reports from cheapo3 I decided to investigate the cause of this. The most efficient, fast and cost effective way of doing this was obviously to just build up a new board and launch it. This also gave me a chance to play around with foil balloons which seem far more suited than small latex for this sort of payload.

I made the 1/4 wave antenna using cat5 cable instead of telephone cable this time around and it seemed to make all the difference! Had lots of great signal reports and a fair few trackers. The software had also been updated with some power saving code dropping the current down to 50mA, and a distance from launch site calculation added. The tracker complete with batteries and foam box weighed in at about 40g.

I aimed for a fairly low ascent, but by just measuring this by eye in quite a confined space (my garage) it was probably a little on the overfilled side. I cannot imagine having to fill one of these outdoors!

Instead of using a plastic tube for filling I simply opened the valve using a drinking straw then filled the 36″ qualatex balloon using the filler nozzle on a disposable 50 helium canister.

I filled 2 small latex balloons to use as wind indicators and to test for tree clearance. Just as well as the first one got stuck!

Launch video:

Unfortunately the balloon did not enter a float despite its fairly slow ascent rate. At about 5400m the balloon started to leak gas. This looked like it was leveling off for a float. But then started to descend at about 1.1m/s.

As the balloon descended I tried to decide if I should go to recover. My inverter went missing and I doubt my old laptop would have lasted long enough to be worthwhile. I sat there and watched as the balloon crossed the River Thames and bounced along between 100-200m altitude as it rode thermals over the town.

We lost contact with the payload at about 60m altitude over Bexleyheath golf club. Just then Steve (G0TDJ) stepped in to save the day! With his mate Ken at the wheel, they drove down to the golf club to take a look around. After a few minutes with nothing seen, one of the golfers pointed them in the direction of the A2 (eek!). Luckily it seems that the balloon was blown to the side of the road by the traffic and up onto the fence.

Steve caught a passer by just in the nick of time to pass the balloon over the fence to him after convincing him that the payload was NOT in fact a bomb and he did NOT need to call the police! A close shave!

As you can see below the payload had landed directly below the tracked position. I can only presume the balloon floated further on and was blown back down the road, or the wind was directed downwards due to the shape of the trees.

So all in all a successful flight. The new antenna is tried and tested. I have some experience with launching foils. The HC49 RFM22B showed slightly less drift than usual, I will be interested to investigate that one further.

Comparison of RFM22B’s (Standard HABsupplies on top, alibaba board on the bottom)

Thanks again to all those who helped track, and an even bigger thanks to Steve and Ken for going out to recover! CHEAPO5 to follow sooner than you may think 🙂

Cheapo3 flight – 14/06/2013

Posted on June 20, 2013 by Chris

Last week I launched a test flight of the new cheapo boards to test how they performed against the old ones. Sadly the results were disappointing with a very weak RF output.

We aimed for a low ascent rate (1.2m/s, which we came very close to!) and released it out to sea.
After the balloon had traveled a couple of miles I noticed the signal was much weaker than anticipated, after eventually losing the signal altogether after about 25 miles.
Luckilly G8KNN (Cambridge), jijdaar(NL) and a few others jumped in to save the day, and managed to track the thing all the way up, and most of the way down (to about 5km).

Sadly the payload did not make it into Europe, however I am glad to have had the chance to test the new boards before relying on them for a much more expensive flight.

UPDATE: On the 30th June 2013 I had a phone call from a woman on the island of Borkum (Germany) who said she had found the (badly damaged) payload in the sea!

I would have loved to have seen some photos of the payload, but unfortunately she did no have access to the internet. After spending about 15 days in the north sea I expect the tracker would have been damaged beyond repair, so I said not to worry about sending it back.

You can see in the (badly edited) image below quite how far the payload drifted from its tracked landing location.

I believe the problem was down to the antenna being made from cheap single core telephone cable (which I thought would be extremely similar to cat5, which works well). I will launch another board in the next few weeks with either a cat5 or a coax antenna and see if there is an improvement. In hope to be able to source a small step up regulator board to allow future flights to run from just one lithium AA cell

CHEAPO R3 boards

Posted on June 1, 2013 by Chris

The new CHEAPO boards are here! I have soldered one up and all seems to be working perfectly! Here is a quick write up on the results.

New board compared to old, looks much neater!

Main components of CHEAPO3

Weight of CHEAPO3 with and without batteries

Micro SD card installed (2GB seems like overkill for text logging!)

Current consumption of board whilst acquiring GPS fix, writing to SD card and transmitting = 110.9mA. This will drop when the tracker gets a GPS fix and if the SD card is removed for long duration flights. I think I will have a go at optimizing the code and look into the power saving modes of the uBlox NEO-6

I am very happy with these boards and look forward to testing one in the air. Currently planning a possible pico launch on the 14/06/2013 (PM)

uBlox UBX ACK code in Python

Posted on May 15, 2013 by Chris

In order to use the uBlox chip in a high altitude balloon, it must be set to flight mode to enable its use up to 50,000m altitude.

This mode is set by issuing a UBX command over the serial port, then checking its acknowledgement (ACK) packet response. There are great examples on UKHAS of how to do this on an Arduino, However my Pi payload code is all in Python, a language I am still getting to grips with.

It turns out it was relatively straightforward to translate line by line, also improving my understanding of how the code actually worked instead of just blindly copying/pasting blocks of example code. I encountered a slight problem when checking the ACK response packet from the GPS against a expected response as the expected response was stored as an integer value, and the actual reply was stored as a character!

My code can be found on GitHub

uBlox NEO 6 GPS module USB connection

Posted on May 15, 2013 by Chris

The NEO-6 is a neat and affordable little GPS positioning chip with a few features which go unused in my other GPS tracker boards. One of these features includes a direct USB connection to the chip, allowing it to be used with a computer.

The circuit is quite simple, consisting of only the ublox chip, a few resistors, and a voltage regulator in order to power the 3.3v chip from the 5v USB line.

My circuit is based around the diagram in the uBlox hardware integration manual (page 12)

The PCB design is less than optimal, but this was really just an experiment into the use of USB.

Result! It works perfectly!

I was not sure at first if it would show up as a USB serial port, or some other kind of input device. However it appears in device manager as a “uBlox 6 GPS Receiver (COM11)” making it nice and easy to program with.

I can also confirm it works out of the box with the Raspberry Pi, accessible via PySerial, making it perfect for the SSDV Pi payload I am also working on (more to follow shortly).

CHEAPO3 boards designed

Posted on May 11, 2013 by Chris

I have just sent off the designs of CHEAPO3 to be manufactured by Hackvana.

Thanks again to Upu for checking over the boards for me and helping with EAGLE.

CHEAPO 2 HAB flight

Posted on May 6, 2013 by Chris

CHEAPO2 – My second balloon launch – Sunday 5th May 2013

After my first launch of NSE we still had another balloon and some helium left over, so we planned for another launch using only one tracker, but a proper canon camera this time.

We went up to Cambridge to meet Steve Randall at the EARS rocket launch site. It was nice to see some of their big rockets going up (despite one landing worryingly close to our balloon whilst filling it).

The wind picked up a little so we decided to reel the balloon back in and try Steve’s “Hail Mary” launch technique. This pretty much consisted of releasing the balloon upwind of the payload, letting it take up the slack, then throwing the payload into the air! As scary as it was to watch it worked very well.

You can just see one of the rockets being collected that landed very close to us in the photo below:

The flight covered about 20 miles as the crow flies and reached and altitude of 24.5km

Flight path of CHEAPO

The Canon A530 camera worked a treat, although my DIY 4x AA battery holder failed just before launch. I popped just 2 lithium’s in the camera but they still lasted the entire flight!

Here are a few photos:

The recovery was nice and easy. We sat around near the predicted landing site with a great signal on the 5/8 magmount, switching to the 3 element yagi when it hit the ground.

The signal was extremely faint on the ground as the antenna got squashed flat on impact! After hunting around with the yagi we got one decode and set off on foot after it.

CHEAPO in flight 808 cam video:

Post flight write up:

The 300g mil surplus balloon expired in 2010 so I am happy we got a decent altitude out of it! However the transmission power was once again very poor. It has been suggested this could be down to a problem with the PCB track on the board, or a faulty RFM22B transmitter module. I will turn the output power right up to hopefully achieve 10mw ERP and do a flight soon to send the CHEAPO prototype to its grave in the skies! Proper boards will be ordered from the board house very soon 🙂

CHEAPO2 altitude/time graph.

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.

CHEAPO budget self etched SMD GPS tracker

Posted on March 29, 2013 by Chris

I have been working on a SMD tracker for a fair few weeks now, but today the last part fell into place making it ready for flight!

The PCB is the second board I have designed in EAGLE, only a few minor details weren’t quite right, but these could be rectified.
It is a topside only single layer board, making it possible to etch at home using the toner transfer method.

Once the board was etched I could solder on the TQFP ATMega168 micro controller, along with its crystal, loading capacitors and 10k pull up reset resistor (a feature I missed on the test breakout board design).

I chose to use the TITLV70032DDCR 3.3v low dropout regulator to power the board. It has a good current output of 200ma and very low drop out, allowing every last drop of power to be drained from the batteries. The thing is tiny, however the pin spacing is reasonable and proved quite nice to solder in comparison with the TQFP which was tricky and requires some practice.

The GPS module is a uBlox NEO-6. It is one of the few modules that continue to work at high altitude, however its software must be put into an airborne mode to allow this. The code on the ATmega waits until the GPS gets a valid fix before putting it into this mode, allowing for a faster time to first fix. The module has built in USB functionality along with lots of other features that go unused in this application. The communication between the GPS and ATmega is a hardware UART port. The GPS gets its signal using a surface mount JTI 1575AT43A40 Chip Antenna. I expected these tiny chips to get a very poor signal. However after leaving the board out to get its first ever fix for an hour or so, the chip can pick up a fix in a few minutes, and usually reports back 7 or 8 satellites.

I ran into problems with the exposed ground plane touching vias on the underside of the ublox. I removed that area of copper with a scalpel and soldering iron which solved the problem. I found the uBlox chip even more tricky to solder than the ATmega, the pins are small and easy to bridge to the metal casing so care should be taken. I actually missed a connection so i had trouble sending the flight mode command, as it simply didn’t make it into the GPS chip. A blob of solder connecting the GPS to the board solved that problem.

For a radio transmitter i am using a RFM22B module. These use the SPI protocol to communicate and have configurable frequency and power output via software. this makes every aspect of the transmission customizable, including shift. The module also has a built in receiver, making it possible for two way communication. However this is unused in my setup. The sending of RTTY is interrupt driven to free up the processor and give it time to handle the serial data. Also timing is more accurate for if i ever want to use a higher baud rate than 50.

If all goes according to plan I will be flying this tracker for testing and as a backup alongside my main payload (NSE) in April. Possibly Saturday the 13th depending on weather, updates to follow!

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.

Chris Stubbs

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

Category Archives: HAB