Vatorex, a Swiss startup developing new solutions for beekeepers needed help developing a new method for low-cost data transmission.
One of the main reasons for the bee mortality which increased in the last years is the so-called varroa mite. In order to mitigate the problem beekeepers treat them using chemical substances. However, this kind of treatment has to be well-timed and can only be used a few times a year. Vatorex is using an alternative approach to solve this problem. They use hyperthermia, which is nothing else than heating up the individual honeycombs to a degree such that only the bees survive but the varroa mites die. In order to improve their system, Vatorex is developing a smartphone app such that the beekeeper can track the treatment status of the individual honeycombs. The problem and reason they contacted Unicorn Labs are, that the smartphone app should enable the beekeeper to identify the honeycombs. However, there is a little challenge involved in building this solution.
How can the app identify the individual honeycombs?
This was already the starting point for our design thinking workshop.
The challenge was to figure out how to transfer only a few identifier bytes from multiple control units, responsible for a group of honeycombs, to the smartphone app of the beekeeper.
The workshop resulted in a priority list of different concepts in order for this low-cost data transmission. On the list, we had transmission using (always transmitting device/ smartphone) audio/ microphone, LEDs/ camera, and magnetic field/ magnetometer. With the latter one as our target approach, since almost every smartphone is in possession of a magnetometer. Magnetic fields also can be generated using just a wire and a current.
As shown below we actually started wrapping a wire around a screw. To increase the field strength a longer screw and more turns have been used. One of the key insights during this breeding was that one can use a simple SMD inductivity in order to generate very strong magnetic fields. We expected those coils to be shielded in a way that the magnetic losses can be reduced. Since such SMD coils are very cheap and can be easily mounted on any PCB we found our ideal solution.
The signal quality of the SMD coil was surprisingly good. We also figured out that the sampling frequency and quality of magnetometers have become better over the last smartphone generations. On newer smartphones such as the Galaxy S7, which seems to have a sampling frequency of 40Hz we can easily transmit data using a very simple amplitude modulation as shown in the plot. The transmission rate in this experiment was 10 Hz. The intensity is normed relatively to the earth’s magnetic field. So the peak signal strength is almost 15 times stronger than the one from the earth.
The SMD coil has been powered using a transistor and the logic has been implemented on an Arduino. Some additional code has been implemented for checksum calculation and error correction using hamming(8,4).
After all tweaks and the one weekend, we were able to transmit reliably using 5 Hz (without any errors in the signal) and 10 Hz using error correction. We also managed to transmit data with 5 Hz using up to 3 cm distance between coil and smartphone. More than enough for a casing to make sure the PCB is weatherproof.
We would like to thank Vatorex for their trust they put into Unicorn Labs and wish them all the best on their further journey towards improving beekeeping.
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