Hi
I need to drive a needle valve (multiple turns) with a continuous servo (like this: http://www.ebay.it/itm/Continuous-rotation-MG995-servo-motor-/151293797605).
I need to determine needle valve fully close position and fully open position.
I thought of keying a sensor (or something) on the servo main shaft.
But in the reality I have not any idea.
Could someone help me, please?
Thanks.
You could put a rotary encoder on the output shaft.
Perhaps you could put a magnet on the shaft and detect with a hall-effect sensor - but that would only detect full revolutions.
Assuming the needle valve moves up and down you could, perhaps use a couple of microswitches re optical sensors to detect the top and bottom position.
If you need no more than about 3 revolutions you could consider a sail-winch servo which has position control.
...R
Hi,
The problem is Multiple Turns for the valve.
The some valve actuators that I work on, have a screw thread, also driven by the servo, that makes a block move along it.
The position of the block represents the open/closed position of the valve.
A couple of sensors at either end of the screw thread movement then detect full open, full closed.
Tom..... 
Ok,
I think to realize something like this:
Could you suggest me some solution (link or ready made)?
Link to sensor?
Thanks.
How many turns? A sail winch servo can do 3.5 turns straight out of the box and some of them can be stretched to 7 turns with very little work.
A stepper motor might also be a useful option. Just drive the valve fully closed, then count steps from there.
akard:
Ok,
I think to realize something like this:
Could you provide a cross-section drawing of what you are trying to make with some key dimensions included?
It is also VERY HELPFUL if you respond to all of the comments that are made - that way, if we have suggested something impractical we will know.
...R
Hi,
The drawing below supplied by
http://www.rocketmoonlighting.com/projects/valves
shows a servo already controlling the valve.
So you will not need feedback to control it.
It probably isn't a multi-turn valve, it would be worth emailing the sellers and finding out any particulars.
Tom...
spv-4.pdf (145 KB)
TomGeorge:
Hi,
The drawing below supplied byhttp://www.rocketmoonlighting.com/projects/valves
shows a servo already controlling the valve.
So you will not need feedback to control it.It probably isn't a multi-turn valve, it would be worth emailing the sellers and finding out any particulars.
Tom...
Right.
The drawing shows a servo controlling the valve but that valve isn't mine.
My valve is a needle type valve with about 25 turns to go from fully close (0%) to fully open (100%).
Definitely sounds like a stepper motor job to me. Fit a microswitch to either fully open or closed position and at the start of the program move the valve until the switch is hit. From then on the position is known from the number of steps.
Russell.
russellz:
Definitely sounds like a stepper motor job to me. Fit a microswitch to either fully open or closed position and at the start of the program move the valve until the switch is hit. From then on the position is known from the number of steps.Russell.
How can I fit a microswitch? Could you draw a mechanical assembly scratch?
I would try it without the microswitches. Just drive the valve hard into the end-stop and then count steps from there.
MorganS:
I would try it without the microswitches. Just drive the valve hard into the end-stop and then count steps from there.
It was my idea.
But I found this:
OpenServo
capable to do this:
Hack your servo v3.00: Get full PID position and speed control from your servo
the question is: where to buy this openservo board?
akard:
the question is: where to buy this openservo board?
Following the links.
http://www.robotfuzz.com/index.php?main_page=product_info&cPath=65&products_id=180
zoomkat:
Following the links.http://www.robotfuzz.com/index.php?main_page=product_info&cPath=65&products_id=180
it is sold out...
Hi
I am planing to do same.
However 1/4 valve is not the best choice, needle valve has much better linearity.
Position of needle can be controlled with hall ratiometric sensor.
kr