Power Connections

We will be using individual power supply to each board (from the computer or Raspberry Pi if connected or batteries if disconnected) and a shared breadboard mounted power supply. The shared supply is capable of providing either 5V or 3V. The purpose of using it is to provide a supply to components that require a different voltage than what is supplied by the board they are connected to.

Thus, components that need a 3V supply, if connected to an Arduino Nano that supplies 5V, or components that need a 5V supply, if connected to a Raspberry Pico or ESP32 that supplies 3V can use the shared supply.

Mount the breadboard power supply on a half-breadboard and make all the power connections from the breadboard power supply to all the breadboards and internally on each breadboard such that each rail has the a supply at the required voltage.

The connection diagram and the instructions below explain how the five breadboards, one for the power supply and each with the four microcontroller boards, should be wired for power.

Note that each full-breadboard has four independent half power rails, two along the top and two along the bottom. Each half-breadboard has two independent half power rails.

This circuit shows the common ground connections which are important when data is being exchanged between boards using the UART protocol.

Connections

• The first half-breadboard will have a breadboard-mounted power supply that takes a 12V input from an AC-DC converter through a barrel jack. This supplies 5V and 3V to each power rail, set by the jumper pin.

• Each microcontroller board will be powered by the Raspberry Pi it is connected to if you are implementing the Node-RED variation of the solution. If using a wireless communication version each microcontroller board will be powered by 3.7V batteries (2 for each Nano and 1 each for the ESP32 and Pico).

• The first breadboard with the Arduino Nano will have two half-rails along the bottom supplying 5V from the board. One half-rail on the top left will supply 3.3V from the external power supply for any components that need 3.3V, and the other half-rail on the top right will supply 5V from the external power supply as an alternative to the 5V supply from the board.

• The first breadboard uses a level shifter to connect a LoRa (SX1278) module which has a 3.3V operating (signal) voltage to the Nano which has a 5V operating voltage. The level shifter will get its 5V and 3.3V supply from the top left and top right half power rails respectively.

• The second breadboard with the Raspberry Pico will have two half-rails along the top and the left half-rail along the bottom supplying 3.3V from the board. The half-rail on the bottom right will supply 5V from the external power supply for any components that need 5V.

• The third breadboard with the ESP32 will have all four half-rails supplying 3.3V from the board.

• The fourth breadboard (a half-breadboard) with the Nano will have both rails supplying 5V from the board.

• Ground connections will be made across all power half-rails regardless of whether they are 5V or 3.3V, board-supplied or externally supplied. Ground connections will also be made across boards that intend to exchange data with each other.

Connection Diagram

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