The high cost of commercially available, motorized 2 inch ball valves (>200 USD) prompted me to build my own actuator (and in the process add some IoT functionality).
My 2 inch PVC ball valves can be turned with a max torque of 7 lb-ft (measured). Ball valves open/close with a quarter turn, so I don’t need micro stepping, high turn speed or more than 90 degrees movement. I can live with 5 seconds or more to turn 90 degrees. For design purposes, I’m considering double the measured torque (14 lb-ft).
A $35 USD Stepper (Pololu Item 2256 : 0.8A, 4.3V, weighing 80g) will provide 0.3kg-cm (20 lb-ft) of holding torque.
A $10 USD Servo (Pololu Item 1046 : 0.8A, 4.8V, weighing 17g) will provide 2kg-cm (134 lb-ft) of stall torque.
I understand the difference between holding and stall torque, but in this use case (ball valve actuator), there’s no need for holding torque (the valve doesn’t move unless actuated upon) nor for surges in required torque (no changes in load or terrain).
So if I understand it correctly, a Servo would be the better choice?
I cannot properly answer your question. What processor will you be using. What is the environment. How far are the valves from the controller. What power is available. This is some of the information you need to put in your question so we can better help you.
Hi @gilshultz. The IoT portion of the project at this point is not an issue. Only the mechanical portion. Addressing your questions: the valves will have to operate on battery (there's no AC close by), hence my choice of low voltage motors. If its a stepper, more than the nominal 4.3V would be required to achieve full torque @ 1A per phase. If a servo, the issue might be the available current. In any case, the power source will be DC and standalone (i.e. battery).
So once I can clear up if a Servo like the one I listed can do the job (and this is where I need help), I will look into an adequate power alternative and start looking into the IoT portion.
MY use of such valves have shown the torque increases with age of the valve. Last one broke the ears trying to turn the valve. Replaced with brass gate valve.
Same problem occurs with 1/2 inch ball valves.
@JCA34F@apf1979 .. my engineering degree occurred in the late 80's, so it's been a while since I had to use conversion formulas (i.e. their permanence in immediate memory is proportional to their continued use), so yeah, curse malfunctioning web searched-conversions (and the haste in looking for them).
Seeing what 7 lb-ft really translates to in kg-cm or oz-in (the units used in Pololu's motor spec sheets), it is clear that I'll need some gear reduction like you mentioned @apf1979 in post #5
@Paul_KD7HB You bring a very good point! Might as well substitute PVC's with brass (or stainless steel) that, as an additional advantage, might require less torque to actuate (today AND in the future). Thanks!
Hi,
What environment will the valve be operating in?
Temperature could be a problem if extreme.
I'm not sure of the importance of the operation of the value but a position sensor and/or limit switches will be a must.
Some motorised valves use limit switches directly connected to the motor wiring to stop the motor at the extremes of travel independent of the control signal.
the motor and actuator are packaged with connectors etc , making a robust unit.
they usually use a hi torque geared motor with limit switches at the end of travel . Motor is often ac and can be easily interfaced with thyristor output controllers.
usually a potentiometer is provided to give position feedback ( used by controllers ).
By the time you’ve built something that good and works you will have spent that .
You can buy a cheap ish 3 term controller to go with it - job done .
I also need proportional water flow: these are interconnected water fountains, one fed by pump/filter, the other fed by the first fountain, and, both receiving rain water, so there's some valve calibrating taking place every day. There's also a 15k liter tank to feed and manage total water fluctuations. That's why I want to add IoT and control the 3 valves (pump, drain of fountain 1 & drain of fountain 2) remotely, to calibrate water flow and maintain water level from code.
Thanks! After these exchanges, I see that now. I could build something that works using 3D printed gears, PCB design, etc. It would certainly be entertaining. But it wouldn't last long. I'll go the way you describe and suggested in this forum entry: I'll change my valves to actuated brass or steel valves and add the controller and DC power supply. Still entertaining but also long lasting
Thanks! Temperature is relatively mild throughout the year (5°C - 28°C). I'll go with a brass or steel actuated valve and add the controller and DC power myself.
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