Another Orbit Yard Watering valve question.

I hate to beat this dead horse any more, and I suspect my question has already been answered (many times?) but after digging around and doing various searches I can’t find the answer so I will ask the question, and the group’s forgiveness. :blush:

I am working on automating a small greenhouse. I have my temp/humidity sensor coming. I have a power supply (15vdc PS from an old laptop) that I have already tested and it operates the Orbit irrigation valve for my mister system, and an 8705 wired to provide 5V to power the Arduino Uno (need to pick up a heat sink). So far so good.

What has me scratching my head is how to operate the valve solenoid. It works by sending a pulse (in this case 15VDC) to open it, and a pulse of the opposite polarity to close. A relay tied to a digital output would work to open the valve but I can’t figure out how to swap the positive and negative to close it. I could use 4 relays operated in pairs, but I know there must be a simpler solution.
Thanks in advance for any suggestions.

Simplest solution would most likely be a small H-driver motor driver rated for the voltage (15) and current (?) your valves require. Some motor shields support two ‘motors’ so two valves per shield. H-drives usually require two digital output pins, one for direction and one a pwm output for speed. In your case speed would be either full or off and direction would determine polarity,

Hi, it seems weird that you have to produce a negative pulse to turn it off.
Can you attach a copy of the information that tells you this.
It sounds to me that a positive step turns it ON, and a negative step turns it OFF.
So apply 15V and it opens, stays open until you remove the 15V then it closes.

Hope to help..

Tom........ :slight_smile:

retrolefty,
Thanks for the idea, that looks like it might be just what I need. Looking into the H-bridge solution now...to bad there is no way I can get my hands on one of them in this backwards podunk town...time for another Amazon order.

Tom, I can't tell you where I learned how these operate, just one of the things I stumbled across while researching. But I can tell you I tried it and it does in fact latch open with a pulse of one polarity, and closed with a pulse of the opposite. When you consider these were intended to operate from a battery powered timer, it makes sense that you would not want to maintain current to hold it open.

Hi, okay makes sense with battery power.
So all the valve actuator is then is a magnetised shaft, the coil around it pushes it in either direction depending on the direction of current.
The valve is what is called an over-centre valve, once you get the shaft past the centre point of its throw it springs over and the same when you reverse the process.
Will need to know what the resistance of the coil is to calculate the pulse current.

Tom....... :slight_smile:

Just wanted to post a follow up. I ended up using a two DPST relay board and it works great.
I have a solid state H-bridge on the way to replace the relays as I plan to use the relays to operate a heater and possibly a fan in the winter.

Thanks for the help.

TomGeorge:
Hi, it seems weird that you have to produce a negative pulse to turn it off.
Can you attach a copy of the information that tells you this.
It sounds to me that a positive step turns it ON, and a negative step turns it OFF.
So apply 15V and it opens, stays open until you remove the 15V then it closes.

Hope to help..

Tom........ :slight_smile:

The reason for the latching action via first positive voltage applied for one state and then negative voltage applied for the opposite state is an energy saving feature as current is only consumed while changing state rather full current required for one of the states. There are latching relays sold and used for the same benefit.

Hi retrolefty, yes it makes sense, see reply #4 where I corrected myself, H-bridge would do the job, just need to see how long a pulse to make the toggle action.

Tom....... :slight_smile:

there is a nominal water pressure required so that the valve 'throws'.....

many, many moons ago I tried using these types of valves to drain a tank.... a very shallow tank... hence no head pressure and the valve would not throw.

however, for a water supply situation... that's different.

Can anyone post a link to an H-Bridge schematic that would work for this application? I am trying to do the same thing. Thanks!

All my Orbit sprinkler valves are "jar-top" solenoid valves. If I'm not mistaken, these valves are closed if no electrical current flows, and they open when power is applied. Power in this case is low-voltage AC, I think 24 volts.

jackricci:
Can anyone post a link to an H-Bridge schematic that would work for this application? I am trying to do the same thing. Thanks!

http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/bjt-circuit.html

Xpendable:
All my Orbit sprinkler valves are "jar-top" solenoid valves. If I'm not mistaken, these valves are closed if no electrical current flows, and they open when power is applied. Power in this case is low-voltage AC, I think 24 volts.

you are correct. there are some battery units that screw on the house spiggot and the hose attaches. for battery power, they use one pulse to open and one (reverse) pulse to close.

the ones for sprinkler systems that are hard wired are often 24V and with power, open, and without power, close.