HAB (PI_CE1) project 2014

PI_CE1 HAB 

We reached 32.379km

Images from flight - https://plus.google.com/photos/117789082000619135339/albums/6056391744489169713?authkey=CKXT9O3I1IHSwAE

Video from flight - http://youtu.be/Hgaklsc14w

Google Earth plot of flight - https://drive.google.com/file/d/0B3Q7HaEVzvrNRUdZbGR2ZmU4M1E/edit?usp=sharing

3D Printed Replacement Battery for GSM/GPS Tracker

So far not had very good results with the GSM/GPS tracker. A lot of it comes down to not being sure the thing is even turned on and not convinced about the batteries. With this in mind i have looked to replace the existing replaceable battery with a 3d printed dummy that can be hooked up to another lithium cell such as a 18650. To keep things simple i removed the contacts from an existing battery so that i would not have a problem getting things to line up.

Still needs wiring up etc but a good start and fits. Will need to cut a small hole for the wires to exit the case, or perhaps make a new back cover :-)

Video camera power

UPDATE:- So some good progress with powering the device with original small battery and a 18650 supplying 5vdc through a cheap booster.  This time the camera functioned till i removed it from freezer after 2hrs20. I was able to still control all functions and stop the recording. Upon checking the sd card had data for all the time span as well.

UPDATE:- Ok so mixed results. Under 18650 power i managed just over an hour before the camera looks to have stopped writing to the SD card. It was still showing LED wise that it was recording but data stopped being written to the card after 1hr 17. Trying in the freezer this time it would seem that at -28Cish the battery was still reading 4.15volts. Condensation was a factor and think might have caused a few issues with recording. Going to rerun tests and see what results are this time.

So with the video cameras we are looking to use they are normally powered by usb 5vdc and only have a tiny battery for things like powering the clock and keeping the system alive for a few minutes after power is pulled. the battery actually within the make and model we are using is only 180mah. First job was to split the camera apart and see the location of the battery and figure out how we can power it for longer with out having to supply 5vdc through the usb socket. The pictures below give an idea of the setup in taking apart and also the battery itself. It was easy once i figured out the first step.

Once i had the camera open i was able to desolder the existing battery and connect up to a bench power supply. From this i was able to supply a stable 3.9volts to the camera and see what power drain detected in the different modes. Camera standby 20ma Camera record screen on 30ma Camera record no screen 27ma this suggest that a 18650 battery would be a good power source for extended records times. The next step is to test to see how well it can operate at low temperatures that it might experience. One positive is that we can separate power source so worse case a hand warmer can be used to keep power source warm while camera is external.

Camera Spin Issues

We are going to use 2 ball bearing swivels (12gm each. Tested at 400lbs) in order to mitigate balloon spin going down to the package.

Another way of reducing spinning is to increase rotational moment of inertia which is basically moving the mass from the center of rotation. As an example of that could be long sticks with some weights at the end.

Video Footage

Capturing video footage of the balloon and its flight is one of the key aspects of the flight we want to achieve. One challenge faced is to weigh up the risk of not being able to retrieve the data or never finding the payload.

A number of good action cameras exist on the market but all come at a high price like the go pro range.

Another option came to mind in terms of a 1080hd video camera. In have for some time been using a dash cam in the car to capture and incidents as they happen in front of me. They come with a wide angle lens as standard and even the cheap ones if you are careful can give good results.

Testing Will need to be carried out against changes in temperature etc but I Will start with a relatively cheap one available from Amazon. They all have tiny batteries as they are expect to be powered from a 12v cigarette socket providing 5vdc through a use socket. In think the battery is only 240mah and just keeps the clock etc powered. First off will be to replace this with a larger power source.

Testing Will be required to also establish how much power will be needed for flight and size of microsd card to capture the whole event.

Balloon Tracking

So a number of ideas for balloon tracking all with pros and cons. So far we have gone with the following two options.

First up we have a basic gsm/GPS tracker which will respond to sms messages as long as it has a signal. I have a isle of man SIM card which should help as it Will roam on all the phone networks in the uk. Helping provide as best a chance of having a signal. 

The other tracking device we will use is a PI in the sky board that attached to a Raspberry PI and provides GPS tracking at high alltitude using radio to transmit the data. The board itself is pre made and comes with a pretty comprehensive setup. This includes the radio, GPS, temp sensor and the possibility to use PI camera to capture and send back images over the radio link.

Pi in sky

We went with this as it would save a lot of development and coding time. It also weighed up the cost against doing it ourselves and also the risk of using a homebrew solution we would not have had as much testing or success behind it.