Simple Electro-Mechanical Device

Could you live with a continuous, rather than discrete function. I'm thinking: mount the gate "hinge" on the "stem" of a potentiometer. You would probably need to pot down (two resistors) the control signal: then feed the output of the potentiometer and the control signal into a comparator. The output of the comparator then controls the power feed to a motor which is geared down and drives the top of the gate "hinge".

Of course you'd have to weatherproof everything.

Does this make sense?

I have gotten through industrial surplus modulating electric valve actuators which are driven by 110 VAC but which operate 0 to 100% in line with an input signal which varies from 4 to 20 mA - typically in the range of 12 to 15 VDC. These can be removed from the valve and put to other uses.

This kind of thing is also very common and much more accessable with pneumatic actuators - where a positioner reads the position of the actuator and forces it to a position appropriate and cooresponding with the incoming 4-20 mA signal.

This may be so far off the mark it is virtually useless - but if you can use standard industrial components and have sources for them surplus it can make things easier and a lot more sturdy.

You might be able to add a motor driven rubber tyre to the gate and a potentiometer as a feedback/position signal.

Most of the devices I see for such work are not really well made with regards "weather proofing" and are sometimes very large and ungainly......

Just a thought!