Bringing a 1990s Alarm System Into the 2020s with an ESP32
Alarm systems, which normally feature magnetic switches to detect door/window openings, along with audible/strobe alert devices, have been a fixture in homes for decades.
As such, many of them feature sensor hardware that works, but which may otherwise be out of date. Brett Laniosh had a nearly 30-year-old Gardtec 800 system (installed in 1993) in his house, which was fully functioning and reliable, but that needed a bit of an update with modern hardware.
To accomplish this update, Laniosh augmented the system with an ESP32 module mounted on the outside of the control box and connectors inside the alarm itself.
Internal connections include power (with a 12V to 5V DC/DC converter), as well as a key switch, latch, and bell output. Signals are transferred to the ESP32 module via a trio of opto-couplers, and a 433MHz receiver is wired in to the ESP board to control the alarm locally.
With this all connected, the ESP32 can generate a simple interface webpage, with alarm set and unset buttons, plus a reset button to silence the alarm when triggered. The system can also send out email notifications. Additionally, the alarm can be set or unset using a wireless remote, which has to be pushed for four seconds in order to avoid false triggers.
Although this may not be exactly what you have in your house, it’s an interesting idea for those that have a “mystery," or "ancient-but-working" control box in a closet somewhere. With a bit of creative hacking, it may be possible to put the existing electronics to even better use!