I was about to add relays to the control box of my projector screen in order to control it with smartthings…
this looks way better, can you add some details?
So as an example the new plan now I guess it would be using a micro controller like NodeMcu or Photon to get the up/down/pause commands from ST and send them via the RF transmitter to the screen just like the remote would, right?
unless if even better if I could avoid using the micro-controller and just add a z wave capability to the screen receiver box.
Correct. Check the frequency of your remote, but the chip/module is perhaps $12 from Amazon, to add to the MCU of your choice. Photo uses the cloud, so ESP2866 or other WiFi or Ethernet Arduino unit is better.
The advantage of using an MCU + transmitter is that you don’t breakdown your physical controller. It remains an untouched manual backup.
Another advantage is you can use the MCU for additional functions such as issuing commands to your Projector via RS-232, IP, or IR … depending on the capabilities of the Projector. And possibly include a 12V in trigger (scaled down to 3V) as a fully local way to trigger the screen RF up/down commands to be sent.
Here’s my Code related to the project (though it is written for SmartThings ZigBee Shield, no longer sold); adapting to WiFi / Ethernet shouldn’t be too hard, especially with “ST Anything” library.