Chet’s Updated Version with LCD display:
For power I will be using the YwRobot 545043 breadboard power supply with an input from the RV’s 12V system. A good functional
description is here: http://www.petervis.com/Raspberry_PI/Breadboard_Power_Supply/YwRobot_Breadboard_Power_Supply.html
Grounds need to be common to all components: Photon, LCD, pressure transducers, alarm
RX to Photon TX
Vin – YwRobot +5V. Must be a minimum of 5V. Don’t parallel off Photon, it works but LCD is barely readable.
GND – from common ground source.
Power via micro-usb port from YwRobot USB port
Pin D0 – to alarm. I was going to use a single relay but have found a controllable buzzer. If it is loud enough I will use it.
A0 – bathroom gray tank pressure sensor
A1 – kitchen gray tank pressure sensor
A2 – black tank sensor
A3- fresh water tank sensor
Ground – Common tie to LCD ground and alarm (or relay control ground if a relay is used.
TX – LCD RX
Red – YwRobot +5v
Ground – YwRobot Negative common to all components
Blue – Input to appropriate Photon Analog pin (A0 through A3)
Vin – YwRobot +5v
Ground – common ground
Input – Photon pin D0