Parts (many similar parts available; I did not do an exhaustive search, and was putting together an Amazon order anyway):
12 V wall-wart with screw terminal adapter:
https://smile.amazon.com/gp/product/B077PW5JC3/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
Trigger cables:
https://smile.amazon.com/gp/product/B075SV1RHT/ref=ppx_yo_dt_b_asin_title_o00_s02?ie=UTF8&psc=1
IR remote relay:
https://smile.amazon.com/gp/product/B07QH6XP9P/ref=ppx_yo_dt_b_asin_title_o00_s01?ie=UTF8&psc=1
No instructions with any of it, natch. I printed out the IR remote relay description from Amazon just to remember the wiring but it is pretty straight-forward. I did solder wires, including couple of short jumpers using scrap wire I had around, but you could use wire splice connectors or just twist and wrap with electrical tape and you should be fine. Voltage and current is low.
Images came out large, sorry -- I just copied and pasted without resizing.
Connect IR box red wire and either the white or blue wire to the (+) power adapter terminal (screws into the green adapter terminals). Connect the black IR box wire and white wire from the trigger cable to the (-) power adapter terminal. Connect the unused blue or white wire from the IR box to the red wire of the trigger cable. I stripped a little extra insulation off the wires, added some jumpers to make it easier to connect everything, soldered the wires, and taped everything including the power adapter. Make sure everything is secure and taped to prevent shorts.
Plug the power adapter into the cable from the wall wart, trigger cable into the SDP-75/Trinnov trigger input, and position the IR relay box and sensor (black bead at the end of the short white cable) where the sensor is visible to the remote from your position. Pull the plastic from the battery on the remote first.
I checked the trigger circuit using my trusty 40-year-old RS multimeter, and then pulled the trigger output from the SDP-75 so I was not cycling everything on and off during testing, but the SDP-75 worked just fine. I was not sure if I could just plug in the trigger and it would work, or if I would have to set something else up on the SDP-75 -- turns out all you need do is plug in the cable.
I changed the SDP-75's power settings in my Harmony One by letting it learn the on and off signals from the little remote, and added a 60-second power-on delay for the SDP=75 to boot (60000 ms). So far so good, working great. I may paint the IR relay box black and muzzle the LED inside so it is better hidden in my room (it is sitting on top of my console at the moment).
Disclaimer: I just bought what was cheap and near the top of Amazon's bazillion-item list with decent (albeit not 5-star, more like 4.6) reviews. Most pieces require a little more work and adding a little box to house the relay and such; this solution was simple to wire up with minimal tools and can be done without soldering if you wish. My work schedule is pretty crazy right now and I just wanted something simple I could plumb and play. I also had in the back of my mind that several (non-technical) folk had asked for my solution and wanted to make it easy for them as well.
HTH - Don
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