/Ohmcontrol

DIY replacement for Fronius Ohmpilot

Primary LanguagePythonMIT LicenseMIT

Ohmcontrol

DIY replacement for Fronius Ohmpilot.

Warning: Don't do this on your own if you're a software-only guy like me. Get professional help from someone who understands electronic shizzle (thank you, Stefan, my dear brother).

Hardware

  • Raspberry Pi
    • Tested with a RPi 3 Model B+, but it should work with any model that can run a Python script.
  • Arduino Nano
  • 3 x SSR Relay + Radiator
    • It should be activated with 3V3 (load voltage) as this is what RPi gives us.
  • 6 x M-F Jumper Breadboard Wire
    • To connect RPI/Arduino with the Relays.
  • Status LED
  • Resistors

Setup

  • Connect RPi GPIO pins 16 and 26 each to a relay (Control +).
    • Those two relays are either on or off.
  • Connect RPi GND pins (any) each to a relay (Control -).
  • Connect Arduino digital pin D10 to the third relay (Control +).
    • This relay will simulate PWM by turning it off for some half-waves.
  • Connect Arduino GND pin (any) to the third relay (Control -).
  • Connect RPi UART TX/RX (GPIO 14/15) pins to Arduino serial pins (RX1/TX0).
  • Connect phase to Arduino D2 (use resistors to reduce voltage down to 3.3V)
    • This is necessary to detect zero-crossing of voltage for switching PWM relay state.
    • Zero-cross-detection works best when no other devices use that phase.
  • Connect Arduino D3 (R), D5 (G) and D6 (B) to status LED.
   Separate phase       Separate phase     |      Separate phase       Separate phase
      from grid          to Ohmpilot       |         from grid          to Ohmpilot
          │                   │            |             │                   │
       ┌──┴───────────────────┴──┐         |          ┌──┴───────────────────┴──┐
       │ Load               Load │         |          │ Load               Load │
2 X    │          Relay          │         |   1 X    │          Relay          │
       │ Control -     Control + │         |          │ Control -     Control + │
       └───┬────────────────┬────┘         |          └───┬────────────────┬────┘
           │                │              |              │                │
        RPi GND    RPi GPIO pin 16/26      |         Arduino GND    Arduino pin D10

Software

Raspberry Pi

  • Flash SD card e.g. using Raspberry Pi Imager.
    • Set all necessary settings so that you can connect to your RPi after it starts up.
  • Connect to your RPi e.g. using Visual Studio Code.
  • Run the following commands to clone the repository and install Ohmcontrol as service: 
    sudo apt update && sudo apt install -y git
git clone https://github.com/johannesegger/Ohmcontrol
cd Ohmcontrol
./setup.sh
  • Check logs 
    journalctl -u ohmcontrol -r

Arduino Nano

  • Compile and upload pwm.ino to your Arduino.