The idea: Moisture sensors with mesh networking talk to a main sprinkler-valve controller. Familiar enough.
The twist? Home-made capsense moisture sensors. Super excited about these. Moisture sensors cost a ton. The typical hand-made sensor uses 2 galvanized nails and is resistive. Nails corrode over time and among other problems, require frequent re-calibration. Enter: capsense using a PCB. Terrific idea and most of all, I'll get to play with raw capacitive sensing!
For the test circuit, I will be hard-wiring it up. As the next step, the mesh network sounds like a great idea for sensors to talk to the controller.
For the controller, I'm using a robotics microcontroller - the NXP mbed LPC 1768. The really cool bit is that code compiles online and generates a .bin. To run this on the target, I just need to drop the .bin in its file system and reset the micro-controller. Love it!
Terminal connectivity to mbed: https://mbed.org/handbook/Terminals
For example: screen /dev/tty.usbmodem1412
So far:
- Controller: I ran the hello world program on mbed for blinking of LED1 and also a test of analog input.
- Sensor: Made a 555 pulse generator of 2Hz frequency with (a different) led blinking and connected the moisture sensor to this to create high-pass filter to modulate the output pulse-width. (I will post the circuit diagram on github once it is tested and ready.)
