Schematics
Click on the picture for a bigger schematic in pdf.
Using a small low power DC pump
Using a magnetic lawn sprinkler valve
Most magnetic sprinkler valves are designed to work with
AC or DC. All of them generate a lot of sparks and ware off
relays and switches easily.
This is because magnetic sprinkler valves contain a big coil.
The best way to avoid wear of relay contacts is to run the
magnetic sprinkler valves with DC and add a flyback diode.
The flyback diode will kill any induced current and reduce the
wear on the relay contacts. The additional advantage is that
you reduce electromagnetic interfrence with other electronic
equipment such as wifi systems and microcontrollers.
Some IBM laptop power supplies provide 16V DC.
Using a magnetic valve from an old washing machine
Be really careful with line power and insulate the wires well. The
magnetic valve must not be exposed to rain or humidity from outside.
Washing machines are made for indoor use only. You need to keep such
a setup in a dry graden shed.
DS18S20 sensor pinout
TS272 operational amplifier pinout
Copyright: Guido Socher, tuxgraphics.org