hencoeloff
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Controlling Solenoid Valve

Mon Oct 23, 2017 7:16 am

Hi All

So I have found many articles online regarding the use of Solenoid Valves, but since I am not an electrical engineer, can someone please explain to me something:

If I were to use a Normally Closed solenoid valve and apply the current it needs, that it will open fully? Do solenoid Valves only have two settings i.e Full Open or Full Closed...there is no way to get them to only open 30% (this is only an example) ? If this is the case that they can only open and close, what would you recommend I use to open a valve certain increments?

jamesh
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Raspberry Pi Engineer & Forum Moderator
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Re: Controlling Solenoid Valve

Mon Oct 23, 2017 8:40 am

I'm assuming you are connected this valve to a Raspberry Pi?
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Please direct all questions to the forum, I do not do support via PM.

PiGraham
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Re: Controlling Solenoid Valve

Mon Oct 23, 2017 8:55 am

hencoeloff wrote:
Mon Oct 23, 2017 7:16 am
Do solenoid Valves only have two settings i.e Full Open or Full Closed...there is no way to get them to only open 30% (this is only an example) ? If this is the case that they can only open and close, what would you recommend I use to open a valve certain increments?
Typically yes, solenoid valves are open or closed and proportional control of, say, a radiator in a heating system, is achieved by varying the time the valve is fully open or fully closed on the order of minutes or hours.
Proportional flow control valves are available and turn a valve with a motor to vary the flow.

Proportional valves might be noisier when mostly closed.

What are you trying to achieve?

hencoeloff
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Re: Controlling Solenoid Valve

Mon Oct 23, 2017 11:20 am

Sorry,

Yes it will be connected to a Pi. Currently checking what will be needed to complete the task.

I am in the process of renovating my bathroom. My Programmer brain is thinking to build some sort of Raspberry Pi controlled tap, where the water to the tap is controlled by a solenoid valve...so when you select a preset on the Pi Screen, it would automatically open the warm water to 50% strength and the cold water to 30% so that it is the perfect heat.

Now I understand that there would be 2 of the valves needed, but to figure out what valves are needed is my main problem. I greatly appreciate all the help you guys are giving

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omegaman477
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Re: Controlling Solenoid Valve

Thu Oct 26, 2017 11:41 am

Some thoughts. On/Off modulating tends to not work that well when you have a very fast rise time, that is the mixed water will rise in temp quickly when the cold is turned off. They are better for systems when you have some thermal mass, ie a radiator or bath full of water.

If the water is coming out into a basin you need to take steps to ensure that a malfunction will not dump 80C water onto your hands.

To do what you want ideally, you need proportional valves, which are motor driven. Effectively opening and closing each tap as needed, proportionally (ie 30, 40 or 80%). These can be very expensive.

I have made up simple cheap proportional valves using big ass RC model servos and ball valves (180 degrees from open to close) I have also used stepper motors, on top of standard gate or needle valves, with a fully closed limit switch to keep things synchronized.

If the mixed water is for a bath, then go with basic on/off solenoid valves, and measure the temperature in the bath.
..the only thing worse than a stupid question is a question not asked.

hencoeloff
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Re: Controlling Solenoid Valve

Fri Oct 27, 2017 6:26 am

omegaman477 wrote:
Thu Oct 26, 2017 11:41 am
I have made up simple cheap proportional valves using big ass RC model servos and ball valves (180 degrees from open to close) I have also used stepper motors, on top of standard gate or needle valves, with a fully closed limit switch to keep things synchronized.

If the mixed water is for a bath, then go with basic on/off solenoid valves, and measure the temperature in the bath.
I am thinking of doing the same....some servos can be real strong. So basically just replace the handle of the ball valve with the servo? Some custom work for the mounting would be needed I presume...not that it would be a problem.

Thanks for your input...really helped me.

hencoeloff
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Re: Controlling Solenoid Valve

Fri Oct 27, 2017 6:32 am

I actually found something here. Costs a bit more than I would have hoped,
but it should get the job done. https://arduino.stackexchange.com/quest ... ow-control

PiGraham
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Re: Controlling Solenoid Valve

Fri Oct 27, 2017 9:42 am

If you are prepared to motorise a manual valve there are a few options.
Mixer valves are designed to mix flows.
Cheap thermostatic radiator valves operate by pressing on a valve with an expanding wax-filled cylinder in the control knob. If you remove the knob the actuating button of the valve is exposed and if you arrange for a motor to press it you could have some sort of proportional control.
A linear actuator stepper motor could do the job.
https://www.ebay.com/itm/NMB-Linear-Act ... 2013820794
I got some of these a while ago and they can apply plenty of force. 10mm movement should suit the radiator valves. You can drive them with the ubiquitous step stick and similar. The valve, stepper and driver together should come in under £10. Then you need to work out a sturdy fixing.

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