Stepper motor controlled blending valve

[MattChan]

Do any of you chaps know of a (ideally 22mm) 3 port valve which is stepper motor controlled?

I'd need a cold input and hot input and a blended output with the mixture set by the position of the stepper motor.

 

[Dan Robinson]

Why?

 

[MattChan]

Why not?

Its for a test rig that I'm building for a piece of equipment that I have designed so that I don't have to pay a chap to sit there and adjust a couple of manual valves during extended life testing.

 

[Dan Robinson]

Fluid type?

 

[Dan Robinson]

Flow rate?

Temperature?

 

[MattChan]

Water
<80deg C
<150l/m

If there is something which is a lower spec it would still be handy to have details as I may be able to limit my test to suit.

 

[Dan Robinson]

Will check my office tomorrow. Won't be a stepper though.

 

[MattChan]

Thanks Dan

What sort of drive would it likely be?

 

[Dan Robinson]

Rotary. I won't have one, but I have a catalogue on my desk.

 

[Agile]

From my recollections there are/were blending valves used in smaller commercial installations which used a 0-10 vdc control voltage to set them to 0-100% flow to the output.

http://www.heatingcontrolsonline.co.uk/mixing-valve-actuator-24v-proportional.html

http://www.syxthsense.com/actuators...e-actuator,-24v,-modulating-0..10v,-feedback/

I think most of these kinds of controls use a 24 vdc supply and a DC motor with a potentiometer on the output shaft and then compares the output of the potentiometer with the DC control voltage to turn the DC motor in whatever direction is required

Very simple but equally very reliable!

Tony

 

[MattChan]

0-10V is very doable, got any info?

Dan, would be a rotary encoder and a dc motor?

 

[Dan Robinson]

DC motor controlled by its own controller.

 

[MattChan]

Thanks chaps it has given me some more magic terms to google.

One of these:
http://www.heatingcontrolsonline.co.uk/mixing-valve-actuator-24v-proportional.html

And one of these:
http://www.heatingcontrolsonline.co.uk/mixing-valve-body.html

Gets me pretty close, juat need a bit more data on them and still happy for other suggestions!

 

[bernardgreen]

Been there, the stepper motor control of valves adjusting the relative flow rates of ingredients to mixers in food processing equipment.

Most valves are non linear and the control system has to be aware of and compensate for the non linearity in flow rate as the valve actuator is moved from fully closed to fully open.

For example a half open gate valve will allow flow that is half the flow when the valve was fully open. But when the valve is commanded to raise the gate to 1/4 of the height the flow rate allowed is less than 1/4 of the flow when the valve is fully open. ( attempts use valves with square cross section were reasonable sucessful but presented other problems )

 

[MattChan]

Thanks Bernard, I had seen some graphs, we will just put a map in our firmware to linearise things.

If we look at something like a ESBE ARA659: http://www.plumbcenter.co.uk/product/esbe-ara659-actuator-property-24vac-dc-50hz/ it mentions one of the properties is a variable run time setting from 15 to 120seconds. What does that property actually mean? I assume it isn't the amount of time you can hold at any one position?