The idea for this project was seeded when a friend asked if it was possible to monitor the actual water usage of a sprinkler system on the the internet. The Flow measurement would tell you if a line was clogged or if a valve failed to close.
Having designed an Imp based controller for the Visible Energy NebulaMaster , I decided that the IMP would be the ideal platform for making this device. Inexpensive flow meters are available through E-Bay that output a pulse stream and fit standard 1 inch threaded PVC pipe. This is coupled in series with a standard Irrigation Valve [ actually up to eight valves in parallel in a complete system]. While searching for TRIAC circuits to use in this application I discovered the Open Sprinkler Project. http://rayshobby.net/?page_id=160. This is a fairly complicated system that uses an ATMEGA chip, an Ethernet controller, and a ISM band radio.
Using an IMP simplifies the hardware design considerably. I designed a board that uses leaded thru-hole parts for easy assembly and provided for the use of the April Imp board for the surface mounted components. The IMP April is available through either Sparkfun or Adafruit along with the IMP SDcard. The board was laid out on Altium and fabricated at Sparkfun’s https://www.batchpcb.com/ [ soon to be http://oshpark.com/] I received at least 10 boards and have used 4 already.
To control the 8 channels of drive to the TRIACS , the IMP is operated in the SPI257 mode connected to a 73AHC595 serial shift in latch. The MISO pin2 is used as a reset for the shift register, while pin 8 is used to transfer the shifted data into the parallel output register. Pin1 is used as an accumulating pulse counter for measuring flow while Pin 9 is used to measure moisture in the soil connected like an ohmmeter with a resistor to VCC.
Preliminary tests show that the Imp can operated the TRIACS as designed and also measure the flow and moisture. at this point I’m trying to figure out how best to construct a server/webpage to control and schedule the IMP Sprinkler functionality