RPEM ESP8266 SDK V1 – Connections


RPEM v1 is a STEM project, providing a flexible Remote Power Energy Monitor SDK for your Green Solar/Wind/Battery/Inverter Energy System.

The SDK is designed to be as flexible as possible for the Home Automation enthusiast.


  • DC Input can be taken from a power supply or existing battery.
    • Typically, this is between 6V and 15V.   15V is the maximum!
  • Opto Pulse Input allows reading of the Meter Pulse, or other requirements.  It can be connected to a range of devices such as:
    • TSL257 Visible Light Photodetector Amplifier Unit
    • 3DU5C Phototransistor
    • GL5528 Light Dependent Photoresistor
    • A 3V3 connection is also provided as well as the input (for TSL257 etc).
    • The OPTO input goes to the ADC, so can also be used for other purposes.
  • FET Output is available to drive an external relay or DC device.
    • Maximum DC load of 1.5A / 100V.
    • Control for this FET via an ESP8266 GPIO
  • RS-485 is a serial communications protocol that allows for long cabling distances in electrically noisy environments and can support multiple devices on the same bus.
    • It is often used on Solar Invertors.
  • I2C is a digital expansion interface.
    • This is provided out to a dual sided header connector, allowing for an OLED display to be easily included for displaying required information.
    • Two connector are provided.  These are mirrored both sides of the PCB to allow for flexible options on expansion too.
  • Channel 1 to 4, are either Current Clamps (such as the SCT-013 series), or for measuring DC voltages (such as battery cells).
    • On the RPEM-1-C, standard 3.5mm sockets are provided so CT clamps can be easily connected.
      • Removing a 22R burden resistor can easily convert a channel to measure voltage, as opposed to current.
    • On the RPEM-1-V, the sockets are left off, so you can wire your preferred options.
      • No 22R Burden resistors are included on the board.  You can add these 0805, if required.
      • The resistance of the potential divider is arranged to measure maximum of 70V DC.
    • Voltages are measured with respect to board common Ground / Negative.
  • USB UART is used for flashing, programming the RPEM board, or for monitoring the output (using the UART communications port).
    • The USB interface mirrors the industry standard D1 Mini and the CH340C UART.
    • The UART uses the RTS and DTR, so removing the need of a programming button (flash boot mode).
  • Dev ADC Inputs, is provided to allow additional experimentation or expansion of the Analogue to Digital interface.
      • Two channels are connected to this solder header.
      • Maximum of 5V input.


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