Q: Bundle sensors with an ESP8266 or separate them?

Hardware
21

The problem with this is that you are adding capacitance to the data wires which reduces the useable length.

For me, I would put each sensor on it's own Wemos D1 Mini and report the sensor values over MQTT. Failures would be easy to isolate and replace.

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22

@SteveMann

Ya i thought bout doing that with a feather https://www.adafruit.com/feather

however because of it being in an industrial freezer and an industrial cooler and needing so many sensors across 120,000 sq feet, the need to run conduit for electrical plugs to be installed, I decided to go with one pie in a waterproof box and run 50 yards each direction vs a box for each unit for the sensor.

I try to spend as little time in the freezer. the air coming off the units is -18deg F and I have to get in a full body suit to work in there. Gloves have to come off for working on small things, holding a screw, handling a drill, motion sensor lights going off because they dont detect you 40ft in the air.

Allot to think about and plan when working in a cold dangerous environment.

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23

I have used the exact IC that Garry H referred to. I bought some Sparkfun RJ45 breakout boards with the view to fitting RJ45 sockets at each end of my system and them using network cables to connect the various devices.
At the control end I have an ESP32 with an I2C keypad and a 2.8" TFT display in SPI. I made an interface board with a P82B715, a 12 VDC buck converter to 5 VDC an INA219 current measuring device, a logic level shifter (3.3V from ESP32 up to 5 volt) and a RJ45 socket. The interface board connects to the ESP32 via I2C. The INA 219 monitors the 12 VDC supply.
The interface board connects to a remote board via (currently) a 5 metre network cable, straight through variety. The network cable caries 12 VDC, 5 VDC and, of course the I2C signals.
At the remote end I have another interface board with an RJ45 socket, a PCF8575 I2C multiplexer, a MCP23017 multiplexor and another INA219 to monitor the 5 VDC suply locally.
THe MCP23017 drives a bank of 8 opto isolated relays on one bank of IO, the other bank reads the remote board address via 4 DIP switches. The PCF8574 reads 8 local relay control switches so the system knows whether a relay is in auto mode, switched off or in manual mode.
This all works reliably and without issues. It is part of my garden irrigation system.
I found an article on line where someone uses a P82B715 as part of a commercial sensor system. That system has a I2C multiplexer on the remote end, they published a very good diagram of the wiring set up.
The key to success with the P82B715 are the pull resistors on both the local and the 'long cables' .

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