I builded the fill tube folowing ideas of this UKHAS wiki page.
As I don’t have something to create a grove, I used a PVC waste water plug that already have some kind of grove by design.
- I strongly glued the flexible fill on it.
- To close the remaining space, I added some wet newspaper sheets to create a temporary “wall”.
- I used a hot glue gun, and let the hot glue fall all around the both sides of the newspaper.
- I drilled a small hole to attach a nylon cord to be used for weighting and to secure to the ground bebore launch.
I was very happy with it.
Looks strong and very easy to build.
The payload had a backup transmission using a USB 3G/SMS dongle (Second hand / 10€) to send SMS with coordinates in case of failure of the NTX2.
As it is useless and waste of battery to power the USB dongle during all the flight, I used a script to power it (using a GPIO and a relay) only when the payload was back to the ground (altitude bellow 2 Km).
But when testing my script and the “hot plugging”, I noticed the Raspberry PI A failed (freeze / reboot) everytime the USB 3G/SMS dongle was plugged.
After some investigations, I found the folowing links explaining about the “inrush current” and the Voltage Droop”
http://theiopage.blogspot.com.es/2012/06/increasing-raspberry-pis-usb-host.html
http://thestuffsido.blogspot.co.uk/2013/05/fixing-raspberry-pi-hotplugging.html
http://therandomlab.blogspot.fr/2013/01/raspberry-pi-mod-to-avoid-shutdown-on.html
The USB.org whitepaper explain:
I n accordance to the USB Specification Revision 2.0, the VBUS power lines must be bypassed with no less than 120µF capacitance of low-ESR capacitance per USB port.
So I soldered a “Low ESR” 220uF and this fixed the issue \o/ !
Note: this problem was known by the RaspberryPi foundation as it seems to have been fixed with the new version B+ that have “better hotplug and overcurrent behaviour”.
Introduction
We previously get some data collected by Habitat server, but in this post, we are using Gnuplot to plot our data.
This is data that has been stored on the payload, not only the data sent to Habitat server during te flight.
Data sent during the flight do not contain:
- Data for every minutes of the flight
- Data about some sensors (like pressure)
To have my files in the same time zone as Habitat, I subtracted 1 hour with date command as bellow:
for i in `cat toto | awk '{print $1}'`; do date -d "$i 1 hour ago" | awk '{print $4}' >> tutu; done
Use of gnuplot
Gnuplot can be installed on Debian with a simple apt-get install gnuplot.
Exemple of commands used to create the graph.
gnuplot> set title "Altitude"
gnuplot> unset key
gnuplot> set xlabel 'Hour'
gnuplot> set ylabel 'Altitude'
gnuplot> set grid
gnuplot> set xdata time
gnuplot> set timefmt '%H:%M:%S'
gnuplot> set format x '%H:%M'
gnuplot> plot 'altitude_data_UTC.txt' using 1:2 w lp
...
gnuplot> set y2tics
gnuplot> plot 'altitude_data_UTC.txt' using 1:2 w l, 'pression_data_UTC.txt' using 1:2 w l axes x1y2
...
gnuplot> plot 'altitude_data_UTC.txt' using 1:2 w l, 'temperature_data_UTC.txt' using 1:3 w l axes x1y2 ,'temperature_data_UTC.txt' using 1:2 w l axes x1y2
gnuplot>
We are lucky, the graph created is similar to previous graphs from x-f.lv
UGGY Payload data
Temperature vs altitude
2 DS18B20 sensors were used (Internal/External)
Pressure vs altitude
BMP085 was used.
It is rated as:
Pressure range: 300...1100hPa (+9000m...-500m above sea level)
So.. I was expecting nothing below 300 hPa… but instead I get something that makes sense up to 34Km… :)
Altitude plotted is from the GPS receiver. (NOT a guess from the BMP085 from calculated pressure)
