Servo Valve

The objective of this design was to create a minimal-cost valve for lab-scale or small scale irrigation systems where water has to be diverted to many individual outlets.

It uses a cheap (~2EUR) Kuman KY66 mini servo to drive the actuator. This servo can be controlled and powered using only an Arduino or ESP-Devboard (some limitations apply with the 3.3V logic level), even though a dedicated servo driver is recommended.

Because the water is contained completely within the pinched silicon tube, the assembly is safe from leakage without the need for water-proof printing on a budget.

Important: The valve is for low-pressure applications only, e.g. with a gravity-fed water supply from a water tank, or using a pump you can turn off, or a tap you can close using a proper shut-off valve.

Note: you will only need one pair of levers provided. I have provided multiple sized levers to adapt to different tubes. Smaller gaps will increase the squeeze on the tube (see below).

Optional Use Cases:

• The valve can optionally be equipped with a second silicon tube. In this configuration it can be used as a source selector (e.g. for either fresh water or liquid fertilizer).

• By connecting both tubes to a small reservoir and opening the them in an alternating pattern, it is possible to deliver relatively precise amounts of water to the plants.

Dimensions of silicon tube i have tested succefully:

• outer diameter (11mm)

• inner diameter (8mm)

• wall thickness (1.5mm)

This worked well with the Levers with 1.9 mm gap. Choose a smaller gap size if using smaller tubes or if the valve leaks.

The silicon tube can be attached to normal vinyl-tubes of appropriate size without any fittings, further reducing cost for the system.

I recommend adding some grease to reduce friction between the excentre and the casing.

Stay tuned for detailed assembly instructions, schematics for ESP32 and code base (arduino and node-red) for controlling a set of valves.

Contributing / Remixing

Version Mk1 (this version):
The valve was modelled in OnShape, you can find the model here: https://cad.onshape.com/documents/1132c43c2f19c7c9a79ef423/w/97052a6bf451478134b1ce24/e/e735540764f66d10d5c7fd92?renderMode=0&uiState=69c6725e7c84bea27af7a81a

Version Mk2 (stalled future development):
After finishing this model, I started designing a better version ("Mk2") to overcome some issues
+ increasing torque to prevent jamming by using a planetary gearbox
+ adding an adjustment skrew to handle different diameters of the silicon tube.
However, I did not had time to continue, but if somebody feels like it, you may want to start from here:
https://cad.onshape.com/documents/2c42cab0075d34067edaadee/w/eab8e151245d60d2d1aad08f/e/e5ab5392d0c83c3c851296bb