Water On/off RC servo

This is a controllable on/off valve used as a water squirter on a small drone.

The small WK-P0025 servo feeds a coupler that has the center hole offset as far to

one side as possible inside a bearing. As the servo rotates it moves bearing and the ring

on the bearing off to one side about 4mm. This is enough to pinch off a 5mm od surgical tubing so that it will hold water pressure. The tubing is filled with a syringe and the tubing provides the pressure to squirt out the water.

Previous to this device I posted a design ( Water Valve RC Controlled) that used a one time switch which worked well

but was a pain to refill. This design resets automatically with different servo positions and

you can just squirt in more water and away you go. Go back to that design and I explain the method to fill the tubing.

The bearings were needed so that the wedge that was created did not demand unreasonable servo current to hold it in a pinched off condition.

Printing the coupler needs an accurate printer, my Prusa MK3S+ did it pretty well, just a little trimming and drilling holes to mount the servo and a hole for the servo screw. I found that printing holes so small is very difficult so I do that later by hand. After I have it assembled and working correctly I take the servo off and put the smallest amount of glue on the servo output spline to prevent rotation under load. Be careful you only glue the coupler to the end of the spline. I use a small 1.7mm x 6mm plastic screw into the servo. This expands the spline slightly and is pretty tight but a little glue won't hurt.

I hope this is useful or at least gives you some ideas on how to make your won device.

Cheers

Kisssys