Hey everyone! I am setting up an automation process for my tiny saltwater tank and have run into a situation with the water supply.
There is a bucket that should be filled periodically with de-ionized water (from an RO/DI unit) and this bucket will be used to top off the evaporated water from the saltwater tank. The issue I am having is selecting an automatic flow control to allow the bucket to be filled up.
The general consensus from what I have seen is solenoids are bad (water hammer, unreliable, and internal parts are made from metals). I have looked into pinch valves but they are extremely expensive, and have found that most settled with a normally-closed motorized ball valve.
Most of these ball valves are large (1/2 inch+) and expensive (100 CAD each+) and are also made of metals. So I have decided to design my own using the existing 1/4 quick connect ball valves (fully plastic).
The thought behind this was to 3d print a housing, use a motor to open the valve, and then have a spring return the valve closed when the power goes out as a redundancy.
I am stuck selecting the type of motor to use. I can measure the torque needed to open the valve, and the required spring tension, etc. But I am unsure of which motor would be able to hold its position against the spring tension, and then allow the valve to shut when the power is removed.
So far It seems that servo motors would be the ideal candidate, but I have also been looking at steppers and DC motors with physical end stops.
Would anyone be able to chime in with where I am headed with this? Any advice would be very helpful.
All the ball valves I have seen and used also have an elastomeric seal between the ball and the housing. There are tons of all plastic 1/2 inch ball valves if you just look at the plumbing section of hardware stores.
But you would have to work out the stall current of the motor to hold against the spring.
A servo can do the open and close and hold, but you would have to check/experiment if it would like being driven back though its gearing when the power disconnected.
You best bet would be to use servos for your ball valves, and have a master water supply valve that is held open by a solenoid.
When you have a power failure the master valve closes.
This would likely be a better alternative than attempting to force a stall on the DC motor, I think that would lead to rapid overheating and then a short life for the motor if kept open that way.
My only worry with the solenoid valves is they are usually short lived when kept open for long periods of time (from what I have gathered from the info online) as they generate a huge amount of heat and are also prone to getting stuck open due to sediment if placed before filtration.
I guess the best way forward would be to just build it and experiment, I haven't got a huge budget so your suggestion may be the ideal case for my situation.
Utter nonsense! Proper solenoid valves have run for decades on commercial equipment. I have solenoid valves on my irrigation system that have worked for 15 years. Look for piloted valves as they take VERY LITTLE current to operate.
consider testing both servo and stepper motor setups if possible. Evaluate them under your specific load conditions to see which maintains the position more reliably and responds well to power loss (ideally with a spring return mechanism that automatically closes the valve).
I disagree. And if you have doubts, you can use bi-stable irrigation valve for example. They only need short pulse to open or close.
How can your de-ionized/RO water have sediments to clog the valve?
Why does so much industrial equipment use solenoid valves if they are so bad? A simple air filled, closed off, vertical pipe connected to the line will absorb any water hammer.
Such impressions typically come from watching amateur Youtube videos of cheap junk, rather than researching quality equipment from reliable manufacturers.
This project was finished about 6 months ago. I used a NC solenoid on the water main coming into the filter and a ball valve fitted to the shaft of a servo for the water going out.
This was not an industrial project, the components I picked out had to be cheap and small as I did not want to pay $200+ for a single solenoid valve that could fit my design.
Given the needs of the project and the equipment that could fit those needs, the solenoid valves researched were found to be unreliable and would need fail safes to be designed into the system.
I agree that there is nothing wrong with a quality solenoid valve used in a properly designed system. But usually the associated costs are prohibitive in hobby systems.
