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