Is there an oscillation happening when powering a 24 VAC irrigation valve? Since the solenoid is being driven by an alternating current (AC), does that mean it goes "on" and "off" at some points of its AC phase (e.g. at zero volt crossing) at a fast rate that no one really notices it?
Electronic – 24 VAC Irrigation Valve Oscillation
solenoid-valve
Related Solutions
I once was looking for a similar thing and came up with following low cost (< 10 EUR) solution, that requires however some handicraft:
- Plant watering valve (normally for manual operation; e.g. Gardena, see picture; < 4 EUR) operated by
- a cheap servo (normally used for RC models; < 5 EUR)
A solenoid is certainly the cheapest and easiest thing you can make yourself. Plus, it's not difficult to direct the flow of the water this way. You don't even need to make a valve. All you need to do is to re-direct the flow of the water.
Since you have a flexible tube, you simply need to move the end of the tube between two positions. In one position it squirts the water down, and in the other position, it squirts the water into a drain.
You can wind the solenoid coils yourself. Just cut lengths of steel rod, and wind coil wire (enamelled copper wire around them).
Push the end of your water tube into a short length of steel tube. The springyness of the water tube will hold it away from the solenoid, and allow water to flow into the drain (This is also the fail safe position. When the power fails, it will drain). When the solenoid is energised, it will attract the tube, and allow the water to flow down and be seen.
You may find that the flexible tube doesn't actually work well as a spring. In that case add a spring. Or, use a fairly long piece of thin steel tube instead of the flexible tube. This will be flexible enough to move the approx 4mm required.
Best Answer
Many irrigation valves use a 24V AC solenoid to operate the valve. The valve is opened or closed by changing the position of a diaphragm or flap which allows or blocks water flow.
During the period of an AC waveform, the voltage of course changes, but the solenoid does not open and close the valve at that frequency because AC solenoids are designed to compensate for the fact that AC voltage crosses zero volts every cycle. It uses a shading coil for this:
Source: Ledex - Comparison of AC vs. DC Solenoids
24 volts is a common choice for irrigation systems because it can utilize smaller gauge wires than say 12 volts, and AC is more suitable for longer distance cable runs, which are common in landscaping applications.