Is it safe for the 202U to be connected to my 20-year old Craftsman garage door opener? How else can know if the garage door opener provides enough power? The three terminals of my opener provide power with both an AC and DC component, so I am uncertain if I get correct measurements of the voltages. Even the wall switch wires convey some power, both AC and DC. Thanks
If your opener provides both AC & DC component, you should measure the AC, and make sure it is less than 24Vac.
For wall switch wires, they don’t matter, because they interface with our relays (which can carry the low voltage, no matter AC or DC).
For more stable operation, I would recommend you buy or find some dedicated power supply, the 12Vdc is quite common.
Sometimes, higher AC voltage will damage our receiver, or for some older doors, it just can’t supply enough power (our receiver relay clicks, but you door don’t move).
Thanks and let me know if you have other questions.