I am trying to connect to my home alarm panel via it's built in serial port. It is made by Paradox and there is a GitHub project that I want to use to integrate the alarm into a smart home setup such as OpenHab or HomeAssistant.
Some things I've learnt/discovered:
- The alarm panel's serial port uses 5V TTL for it's serial interface
- The serial port's power and GND is connected to the panel's AUX rail, which is at 12V.
- The ESP can survive 12V input, but the onboard regulator gets very hot.
- The ESP needs 3.3V for it's serial ports.
The ESP32 I'm using is a NodeMCU32-S clone (link to the actual supplier I used).
My initial solution
My power source is the 12v rail from the alarm panel - I would like the whole thing to be self contained. I need to convert this 12v to 5v for the serial on the alarm panel's side, and I need a 3.3v source for the ESP32 side of things.
- Can I use the LM2596 to bring down the 12v to 5V and then power both the HV side of the level converter, and the ESP32 with it?
- Can I then use the ESP32's onboard regulator to further bring that 5V down to 3.3V, that I can then use on the LV input of the level converter?
I'm asking before I do anything because the alarm panel is expensive and important for my home security. I don't want to do something that might destroy it.
My electronics fu is extremely limited, and I learn as I go along.
See below my suggested circuit for this idea:
Your assistance and expertise will be greatly appreciated!