Water Valve Relay Controller Using an Orbit 27987 Water Valve
Keep your Bird Bath Full using a Mister
DIY Electronics Project

6/14/2011

I needed a way to control the water for my bird bath. I have a low volume water mister that I use to keep the bird bath full.
The birds love the mist (especially hummingbirds). They fly in and out of the mist and then land for a drink of water.
The other birds love to take baths.You can see my live birdcam here.
I want the water to turn off at night to converve water and save money on my water bill.

So I designed this circuit using a GE model 15089 digital timer and and Orbit 27987 water valve.
The bird bath water comes on at 6 AM and goes off at 9 PM.
Using the GE timer, I can program any time and duration I wish (something you cannot do with standard water timers because most of them limit the amount of time the water can be on).
The other nice thing is that the water valve is separated from the electronics. If the valve ever leaks or becomes defective, It is just $15.00 to replace.
There is no battery to worry about.

If you have comments or questions, you can leave them in my blog at http://watervalvecontroller.blogspot.com/
I also built one for use with a lawn sprinkler system using a rain water sensor. That project is here.

Build one yourself
But First a Note of CAUTION!

This project requires prior experience building electronics circuits (Soldering skills and basic knowledge of electronics design).

The Orbit water valve operates on 24 volts DC. It has two pins: applying +24v opens the valve, and -24v closes the valve. It uses a latch solenoid, drawing power only when you open or close it. This makes it very power efficient.
However, it just needs power for a fraction of a second. During your testing, do not apply continuous power to the valve.
It will smoke in a few seconds with continuous power applied and you will be off to Home Depot for a replacement.
Make sure you install the capacitors and diodes with the correct + and - orentation.

Also, make sure you use a pressure regulator in line before the Orbit Water Valve. When the water valve closes, it closes fast and can cause a water hammer effect unless you use a pressure regulator. If you choose to ignore this advice, the Orbit Water Valve may start leaking badly. If it does leak, it is easy to fix. Just pry it open and you will see that the solenoid needs to be screwed back in (an extreme water hammer event can even blow the thing apart but it can be put back together easily. Just use a pressure regulator to avoid the hassle. Here is the low pressure regulator I use for the bird bath mister.

How it Works

When the digital timer turns on, it sends 115 volts to the 12 volt power supply which turns on the relay.
The relay is a double pole, double throw relay. One pole has +24 Volts DC and the other pole is the negative side of the 24 volt power supply.
When the relay turns on, a capacitor charges and releases a +24 volt pulse to the water valve to turn it on.
When the relay turns off, another capacitor charges and releases a -24 volt pulse to the water valve to turn if off.

NOTE: The 24 volt power supply is not shown in the drawing below.
The 115 volt power to the 24 volt power supply does not need to be always on. It can turn on and off with the timer.
This is due to the fact that it has enough residual charge left in it to send -24 volts to the water valve as it is shutting down.

NOTE: the capacitive circuits take approximately 7 seconds to discharge. During your testing, you must wait at least 7 seconds after turning on the water valve before you can turn it back off.

How Much Power Does it Use?

With 115 volts ac applied to the circuit (timer on), it uses 5 watts of continuous power. That includes the 1/2 watt the timer uses. The higher power required to switch the water valve on and off is not a factor because it is just a fraction of a second when it is turned on or off.

The Circuit and Components

Water Valve Controller Installed
(Cover off)

I used an aluminum box that is waterproof when the cover is on.
The box is available at Fry's Electronics.
Components are installed on perfboard and mounted in a plastic box.

Rich Love richlove@mac.com

Bird Bath with Low Volume Mister controlled by the the Water Valve Controller

Water Supply Components

All of the following parts are available at Home Depot.
The water valve is made by Orbit.
The rest of the parts are DIG Corp parts.
NOTE: The 1/4 in. Compression Fitting can be hard to find.
However, it is included with the DIG Patio Watering Kit (Model FM01)
Sprinkler Warehouse is a good source online for DIG parts