Clever Geek Handbook

Smart Fishing at FishSensor





โ€œA bad day at fishing is better than a good day at work.โ€ There are a huge number of electronic bite alarms. My version is distinguished by the presence of WiFi with a WEB application, an accelerometer and wireless charging, protection class IP68. The deviceโ€™s brain is the smallest Vocore2 Linux computer, MPU6050 accelerometer, Qi charging based on the BQ51050BRHLT . Sources can be downloaded here Github .



Specifications FishSensor:





The device is structurally a board on which the receiver antenna and Qi charging driver BQ51050BRHLT , accelerometer MPU6050 , Vocore2 connector, battery are located. Dust and water tightness due to the heat-shrinkable tube, from the ends it is filled in with silicone compound Rexant PK-68. Pull the fishing lead through a plastic tube with an inner diameter of 2 mm.







PCB manufacturing



The question was sharply whether it would be possible to make a Qi inductance coil of a receiver measuring 25 x 25 mm, 14 turns, track thickness 0.3 mm, a gap of 0.2 mm, and what the actual inductance of the coil would be. The calculated data were confirmed and gave an inductance of 4 ฮผH.















Soldering Elements











Qi charge setting



An interesting point was the tuning of the resonance of the oscillatory circuit. Recommendations and calculation formulas of datasheet on BQ51050BRHLT were confirmed. Inductance 4 ยตH, inductance with a ferrite shield 7 ยตH, capacitor in parallel 6.5 nF, capacitor in series with coil 422 nf. The quality factor of the circuit turned out to be very low 22 because of the large coil resistance of 1.7 Ohms (a quality factor of more than 500 was recommended by a datasheet). Nevertheless, everything worked perfectly, stable resonance at a distance of 10 mm from the transmitter coil.







Constructive miscalculation - the charge indicator is on the antenna side, i.e. it is not visible when FishSensor lies on the transmitter of the charger. But the charging process is visible on the indicator of the Qi transmitter itself.



Accelerometer Setup







Software



Onboard Vocore2 from the factory installed OC OpenWrt 05/15/1 "Chaos Calmer". The device is accessible via WiFi via a browser thanks to the pre-installed Luci. We use the AP access point mode.

Installed the php5 package and all the necessary libraries to form the web interface. Installed a package for MPU6050 from leon0516 . At startup, I placed the autorun files of the MPU6050 driver and my script written on the 6050.sh bash . The MPU6050 driver generates a text file of accelerometer readings /tmp/mpu6050.txt. 6050.sh analyzes only changes in the Z axis in the file /tmp/mpu6050.txt and writes its log to /www/mess.log. The setup and display pages are written in php.



We connect the smartphone to FishSensor as an access point. Install on the desktop from the browser as a Web application. For Android, in the browser settings, we enable autoplay of sound files (in iOs, such a feint is prohibited by a security policy).







Faced the problem of caching data written to a text file by the OpenWrt operating system. The accelerometer readings are written to the file when the memory cache is full, sometimes delays reach up to 1 second. An existing patch to turn off file caching is broken. I thought that for my task this is not very relevant and decided to leave the problem until better times.



Demo





Full-scale tests have not yet been carried out, they are planned this month.



PS The development of the idea can be a cordless screwdriver with a Vocore installed in it to hook gear at the time of bite. In the maximum development, the Yandex.Fishing service.


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