I recommend that you watch the measured Irrigation video:
An amazing water-saving invention - Universal Measured Irrigation Controller
https://www.youtube.com/watch?v=57bB5z2vNtA&t
 
The Universal Mesaured Irrigation Cotroller includes:
	
evaporator
	
cylindrical float
	
eight float rings
	
float switch
	
adljustable control dripper
	
control box 
	
light sensor 
You can upgrade any irrigation system so that all your plants are irrigated automatically by smart irrigation. Measured irrigation is a new method of irrigation scheduling that responds to the prevailing onsite weather conditions. This means that you use much less water without affecting the yield.
 
	
Fully automatic
	
Smart irrigation controller – the irrigation is controlled by the prevailing weather conditions rather than a program
	
Use for both gravity feed and pressurised irrigation 
	
Use for any size irrigation system regardless of the size of the solenoid valve
	
Use for sprinkler or drip irrigation
	
Use for weeper or soaker hose irrigation
	
Use for pressure compensating or non pressure compensating drippers.
	
A light sensor provides the option of irrigating at night time only without using a timer
	
You can adjust the water usage by adjusting the control dripper
	
You can adjust the irrigation frequency by adjusting the float
	
Adjusting the water usage does not change the irrigation frequency
	
Adjusting the irrigation frequency does not change the water usage
	
The water usage is directly proportional to the net evaporation rate (this is a unique feature of measured irrigation)
	
Respond appropriately when there is an unexpected heat wave
	
When it rains, water enters the evaporator and delays the start of the next irrigation
	
The water usage is independent of the water supply pressure (this is a unique feature of measured irrigation)
	
Uses much less water without affecting the yield
	
Simple and low tech and so there are fewer things to go wrong