I wanted to keep my wired alarm (Veritas 8) functioning how it does today but add onto it some smartness. I didn’t want to rely on anything that may reboot or go off-line for security so I added a node mcu, a pcf extender and a relay board.
I mounted everything next to the alarm panel in an old double socket box, but removed all the guts and added a reset switch, which actually is never required, it seems pretty stable. I used a cheap ali express buck converter to get the correct voltage for the node mcu.
Here is a pic of the contents when I tested on the desk:
I used a node mcu with esphome and a pcf 8574 board:
The relay board has 6 relays, to can control 6 buttons. The I soldered this header onto the board so I could “simulate” kay presses. The keypad is organised into a 4 x 4 grid. 1-4 along the side, 5-8 along the top.
The node mcu monitors two pins on the veritas PCB, therefore “knows” when the strobe is firing and also when the alarm is set of unset. The tricky bit for me was that the pcb outputs 12v, and the node mcu wants 3v. Therefore I brought the voltage down by connecting 4 resistors between these pins and a ground, then taking the feed from between 3 and 4 resistors, therefore bring the voltage down to ~3v. I have an automation that sends me a message via pushbullet if the alarm is triggered.
I have made a keypad in lovelace using the button card.
There are scripts than are executed when the “right” buttons are pressed. Thus 3 numbers (my code has a number that repeats) full set, part set and reset. The script fires the relay for 700ms, which is long enough to register a key press. So, in effect I can press any of the important keys from anywhere.
Next steps are potentially to monitor all the zones - need to check the voltage on the zones and make them ~3v again so the node mcu is happy…
Overall it’s cheap and cheerful but gives a tidy solution to making a dumb alarm smart. Happy to help if anyone needs any more details.
Trux