Liquid Solenoid Pulse Width Modulation for Flow Rate Control

[dm333709]

Hi, I am working on a project to control the flow of water through a line. I need to be able to create a range of flow rates, not just on/off. I found proportional valves, but they are too expensive for our budget. I was thinking of using your "BRASS LIQUID SOLENOID VALVE - 12V - 1/2 NPS" with pulse width modulation to provide various flow rates. What is the response time and accuracy of the valve? Also, if there are any other methods of controlling the flow that I should look into, that would be great. We did look into pumps but decided that is not the route we want to go. The water will just be flowing from a bucket.

[zener]

What range of flow rates are you trying to achieve?

[dm333709]

Anywhere from 1-7 gal/min, but the project guidelines are not strict so it is flexible. The max would be approximately 7 gal/min though since we are just relying on the pressure due to gravity from a 6 gallon bucket to force flow, so as long as it does not exceed that, it should be fine. Does this seem doable?

[zener]

Sure. The issue with a solenoid is it does not turn on and off very fast. I would think 1 Hz would be about as fast as you would want to cycle it. So you would get a pulsed flow, but you should be able to get average flows in those ranges. Luckily it is not a big investment to test it. Another way to go might be to use a servo to create a pinch valve with some tubing. I think that has been discussed before so you might search on "pinch valve". If you need really accurate flow then you might need a flow sensor to give you feedback.

[dm333709]

Yeah that's what I was thinking. Since it is $25 instead of the $250 proportional valve I found, it doesn't hurt to try it. Just wanted to see if there were any obvious issues before I went with it. I have not looked into pinch valves yet, so I will see if that could do what I need. Thanks for the help!

[adafruit_support_bill]

A pinch valve is pretty easy to implement with a servo. You just need some silicone or latex tubing and some mechanism to pinch it. There are a few designs for pinch-valves up on Thingverse: http://www.thingiverse.com/thing:12311