Hello @toddelbow,
My house is also with old ADT system, and I never use it until few weeks ago until I found and followed instructions from this topic:
Connect wired alarm system sensors to SmartThings with a NodeMCU ESP8266
It is big success. Finally I can see status for all my doors & windows.
Few tips:
- You can buy NodeMCU (with base from Amazon) or few $$ cheaper from alibaba (give extra time for shipping).
- My ADT board supplied 17V AC to sensors, and I had idea I need the same. Wrong, 3V3 from ESP2866 is more than enough. Just connect one wire to GRD and second to the digital input.
- There is big chance your existing sensors are grouped together (per part of the house). You can detach each sensor and add it to its own ESP2866 input.
- You cannot use all ESP2866 input but max 5 per board. So if you have more than 5 doors & windows buy 2 or 3 of them (ESP2866 boards). I have 2 and they work like a charm.
- If your ADT board is hidden somewhere in basement of the house, be sure to get Wi-Fi extender that will hook system to your network.
- Have a fun