TESTS OF THE PARACHUTE
PARACHUTE TEST EQUIPMENT
This equipment may be used to eject the can with parachute from, for example, a hexacopter. It has same size as a real CanSat.
MECHANISM OF ACTION
1. Closed – The wire is in the white tube.
All equipment ready to attach in to the Copter frame
1 – Fake cansat
2 – Weight on the rope
3 – Parachute cover – after unlinking the parachute moves up and spreads
4 – Rope connecting to the Copter frame
The tests were done to check the speed of a parachute descent. The Octocopter flew to a known altitude - the data were obtained through the OSD and GPS.
Then our parachute test equipment has been unlinked from the copter. While it was falling, the time was measured.
Preparations before the flight, start-up parachute test equipment
The Octocopter with Cargo
After unlinking, the opening of the parachute – photo from copter and from the ground
Our parachute is made from waterproof material. The velocity of descent is about 10-11 m/s, depending on the weather.
Parachute with 30 cm ruler
Parachute during the flight
- weight: 6g
- diameter: 35 cm
- hole diameter: 4 cm
- lines’ length: 30 cm
We have already done our Geiger counter. Ionizing radiation sensor is one of the most important sensors in our CanSat. It should be solid and built carefully due to fact that Geiger counter needs a high voltage power supply. On the other hand, to amplify very weak signals from Geiger tube, sensitive transistor must be used. High concentration of water vapor can cause short circuits and it can carry an electric charge.
The picture below is showing final electronic scheme.
Using Eagle we have also drawn printed circuit board:
Boost converter and amplifier for our Geiger tube.
Geiger tube leaned against the can.
Weight: 27 g (20 g boost converter & amplifier, 7 g – Geiger tube)
Input voltage: 7.4 – 8.2 V
Output voltage: 340-450 V
Ionizing radiation measurement range: up to 1440 uSv/h
We have created two pieces of test software in NI LabView.
The first application can show current level of radiation, measurement error, and counts how long an experiment lasts.
The second application shows signal from Geiger tubes – each vertical peak in the plot represents one elementary particle.
We have a new sponsor, which is the AVT shop. The AVT shop has given us a lot of the necessary elements. Among other things humidity and temperature sensor SHT11, integrated circuit ATmega2560-16AU TQFP100, 3260 prototype board pin contact areas 4T7D BB-01 and many electronic components.
Last weekend we performed tests of our transceivers using different antennas and data transmission rates.
We tested two different antennas on the transmitting side (the equipped one and a simple wire) and two on the receiving side (the equipped one and a large directional one). All tests were performed with a 9600 baud rate.
We started by testing the equipped antennas to determine the safe data rate — one that would result in no or minimal data loss. While the guide recommended using 60% of the baud rate — which would be 5760 bits per second for 9600 baud — we discovered that it still resulted in minor data loss when transmitting data on a distance on about two-three metres and decided to use 5000 bps, which resulted in no losses.
We constructed two testing sets using the transceivers which could have their antennas easily swapped and rugged them against wintery conditions, so they could be used outside. They also allowed us to reprogram the transceivers to use a different baud rate, although we never used this feature.
Michał wrote a pair of Python scripts to test data transmission and integrity of received data. One would send a series of numbers via the serial interface, starting at one, repeating each one twice, at chosen speed; the other would receive data, display information about number of received items, and compare their validity (whether one number of the pair matched the other).
We placed the transceivers on two hillsides facing each other, on a distance of about 1050 m. We were transmitting data using the equipped antenna and receiving it with the large directional one.
We performed all tests using 9600 baud rate with 5000 bits sent per second.
In a series of tests, we discovered that although there are no concerns about data integrity nor data loss at this distance with this hardware, the antenna only provided a range of about 90 degrees horizontally and 60 vertically; when directed outside this range, it sharply stopped receiving any data.
This prompted us to conduct another test at a larger distance, and to test the capabilities of equipped antenna as a receiver.
We placed the transmitter on a large hill (approx. 300 metres prominence) and the receiver on a plain below it.
At first we tested all combinations of antennas, on a distance of about 800 m. We confirmed the large antenna results, and we discovered that the equipped antennas were able to talk to each other on this distance with virtually no data loss. We received almost no data from the simple wire-based antenna, though.
Afterwards we tested the large antenna on a distance of about 1500 m. It was able to receive data with no losses regardless of the direction it was pointed at, proving that it has a minimal range it can operate at. While we managed to receive data with the equipped antenna as well, we had approximately 20% data loss, making it unviable for our purpose.