Without going into too much detail:
Alarm System : Risco Lightsys2. Nothing unique here, each PIR (and sensor, door contacts, etc) gets 1.5 terminals on the motherboard / "zone expander" (the mobo only allows for 8 devices). 3 terminals shared between 2 sensors, with one common wire.
PIRs : Bosch 4 pin PIRs (well, 6 if you include tamper) connection. 12V is available at each PIR. The pins are essentially 12+ 12- Data+ Data-.
I have a very feature filled OpenHAB setup running (about 20+ types of devices). I would like to bring the PIRs into the fold. They kind of already are, via the RISCO API. But naturally this is not ideal. The API doesn't pick up / broadcast many of the sensor events (seams like only what is "active" during a 5 second cycle or something), there is often a delay of 1-5 seconds between when the events take place and when I know about them and frankly I would rather not hammer their API every 2 seconds to pool the status of my PIRs.
a) Tap in at the panel. b) Tap in at each PIR.
I would much rather go with b for a few reasons. Alarm box is a mess (not my setup), I have never installed an alarm so my know how of how it all works is fairly limited.
So everything is pretty straight forward. Install an esp8266 at each sensor and pull the signal (via the analog pin) of the led that lights up every time there is motion.
The only issue is, I am concerned that the alarm power supply will not tolerate 9 x esp8266 devices.
So, questions are as follow:
a) I see that my alarm essentially has a standard "black" power supply that I can exchange. The manual states that it is possible to install a 4A supply. I have not yet checked the amperage of the existing power supply, so it could be either 1.5A or 4.0A. Its possible I am already running the higher amp power supply as we have quite a few devices plugged into the alarm (zone extenders, 2 wireless receivers for the outside sensors, the siren, etc). If the power supply is of a lower amperage, is it just a question of installing a more powerful power supply?
b) Could someone help me to convert 300ma @ 3.3v to the amperage at 12v (before the voltage regulator I guess...)? My knowledge of electronic conversions is pretty weak and the best I could come up with was 50-100ma @ 12v.
c) Am I correct in assuming that a ESP8266 device will pull 200-300ma @ 3.3v @ peak (eg: packet send and start up)?
d) Even if the power supply at the alarm is of a higher amperage I would still be concerned about the effect when (for example), power has been lost to the alarm, and everything starts up for the first time (this would only take place after the battery has died, but regardless). 9 esp8266 devices hitting the "startup peak" at once?
Any other suggestions / advice would be appreciated.