The Terracotta Irrigation Controller for Solenoid Valves can be used to control non-latching solenoid valves only. It can be used for automatic sprinkler irrigation or drip irrigation. The Terracotta Irrigation Controller has an unpowered valve that operates with water supply pressure in the range 10 kPa to 800 kPa. The interval between irrigation events responds automatically to the on-site prevailing weather conditions (namely, evaporation and rainfall). 
 
Terracotta is porous and so the water level in the pot falls as water seeps through the pot. A float inside the pot floats on the water. When the water level reaches the low level, a magnet inside the float activates the valve so that the valve opens. A signal is sent to the control box and the irrigation starts. During the irrigation event a control dripper drips water into the pot and the water level in the pot rises. When the water level reaches the high level, the magnet inside the float disengages from the valve so that the valve closes. After a  short delay (less than 2 minutes) a signal is sent to the control box and the irrigation stops.
 
During an irrigation event, the control dripper replaces water that has evaporated since the previous irrigation event. This volume is called the control volume. Without the booster, the control volume can set to any value between 105 ml and 395 ml. 
 
Key features
Use for any size irrigation application with any size non-latching solenoid valve
Water supply pressure 10 kPa to 800 kPa
Use for sprinkler irrigation or drip irrigation
Use for gravity feed or pressurised irrigation 
Adjust the water usage rate by adjusting the control dripper
Adjust the interval between irrigation events by adjusting the float
Responds automatically to on-site evaporation and rainfall
The irrigation frequency increases significantly during a heat wave
For sprinklers or drippers, the water usage rate is independent of the water supply pressure
Irrigate directly from a rainwater tank without using a pump
Water in the terracotta pot is protected from debris, algae, mosquitoes and thirsty animals
A light sensor  provides the option of irrigating at night time only
Uses much less water without affecting the yield
Simple and low tech, and therefore fewer things can go wrong
Leave your irrigation application unattended for months on end