On Sunday, 19 April 2020 14:02:19 UTC+1, Pancho wrote:

Requirements:
inching (turns on for ~1 second then off) switch on ~24v ac circuit.
https://ewelink.coolkit.cc/?p=143. Opener is chamberlain liftmaster,

An alternative is a door bell type push switch, inching = momentary
turns on when you press and then off when you release.

That's good, and would be the easiest way. You'd want the 'toggle' switch mode in the Shelly for that.


Originally I used a 443 MHz remote key fob. These cost about £30 each to
replace, ebay clones seem to be ****.

My sonoff switch cost under £10.

A Shelly 1 is under £10 (just), excl. postage though.

The rPi is a nice solution as it is a transferable skill to other things
I want to do. rPi is also standard, i tend to lose the will to live
trying to understand bespoke hardware and software.

A Raspberry Pi is not what I would regard as standard. There are an infinite ways you can build both the software and hardware. Of course, that's a common benefit but it also means quite a learning curve. Lots of tutorials on the web though so you're not on your own. Configuring a Shelly via the GUI could not - I genuinely think you'd be up-and-running in 30 mins.

My preference would be a simple cheap low voltage switch like sonoff
(with tasmota) driver, powered off 24v ac (actually slightly higher) or
usb if available. But only if it is documented and simple.

The Shelly 1 will work perfectly and ticks all the boxes bar running off 24v AC so you might have to rectify that to 12/24v DC.

Still get a Pi though; but don't stifle it life as a garage door opener - there are plenty of other more exciting things to do with it and learn from!