Assembly Questions


My food computer is together but while testing the actuators I’ve run into a problem.

Light panel #1 is plugged into AC2 and comes on with the serial command but light panel 2 does not. The heater comes on but the humidifier does not.

As I started digging I actually see a discrepancy between the way the AC module should be wired per the written instructions and the visual layout on the Electronics Schematic. I did my wiring per the written instructions in the Motherboard Assembly Guide, so do I need to go back and re-do it based on the schematic?

The schematic also makes it appear that panel 1 and 2 are both plugged in together in AC2 but the instructions on how to do this are missing from the Motherboard Assembly. Should they really both be plugged into port 2? Likewise, the schematic says that AC1 should be the humidifier but the Motherboard Guide says AC2.

Thanks in advance for any help!



@CISTiffany, I’m assuming that you’re building a PFC v1 and that when you say “written instructions”, you mean these pdfs: MotherboardAssemblyGuide.pdf, ElectronicsSchematicLarge.pdf, and Food Computer basic P&ID V1.1.pdf.

Disclaimer: I haven’t actually tried this on PFC v1 hardware. What I’m suggesting is based on my reading of the code and docs on github.

Short answer:

As you pointed out, the Motherboard Assembly Guide gives instructions that are inconsistent with the Food Computer basic P&ID V1.1.pdf schematic. You should go with the schematic because it agrees with the Arduino code.

If your Arduino is running the code from OpenAgInitiative/gro-microcontroller/src, then it’s expecting that:

  1. “AAHU 1 1” should turn the humidifier on with pin 9 wired to the relay for AC port 1

  2. “ALPN 1 1” should turn on the grow lights with pin 8 wired to the relay for AC port 2

  3. “ALPN 2 1” should turn on the “chamber illumination” with pin 53 (schematic says this is a 12V relay)

  4. “AAHE 1 1” should turn on the air heater with pin 6 wired to the relay for AC port 4


  1. Change your protoshield AC relay wiring to match the list above–wire it like the schematic.

  2. Plug both grow lights into the outlet for the AC2 relay. You could use a short power strip.

Long answer:

Don’t take my word for it. Have a look at the Arduino code, verify that your serial commands are changing the Arduino’s output pins, and use a meter or scope to trace the output signals through your wiring all the way to the relays and outlets.

Here are some troubleshooting questions for you to consider:

  1. Is your Arduino running the code from OpenAgInitiative/gro-microcontroller/src? The Motherboard Assembly Guide says to use OpenAgInitiative/gro­controller/src, but that actually doesn’t exist.

  2. It sounds like you already followed the troubleshooting steps in section “14. System Testing / Debugging” of the Motherboard Assembly Guide. When you say light panel 2 and the humidifier didn’t work, I’m guessing that means “ALPN 1 1” turned on one panel of your grow lights but sending “ALPN 2 1” and “AAHU 1 1” did nothing. Is that right?

  3. What are you using to connect the Arduino to the Grove cables for the relay board? Did you wire wrap your own protoshield like the Motherboard Assembly Guide describes? Did you use a continuity tester to check between the Arduino header pins and the Grove connectors for shorts or other mistakes?

  4. Did you test the LED strip (light panel 2) and humidifier to make sure they work independently of the relays?

  5. Did you test the relays with 5V to the input pins to make sure they work independently of the Arduino and protoshield?

  6. If your Arduino is running the code in OpenAgInitiative/gro-microcontroller/src, then gro-microcontroller/src/module_handler.cpp is where all the pin assignments and serial commands get configured for the actuator modules. This is the authoritative reference for how the Arduino expects the relays to be wired.

    This is a summary of the actuator configuration from module_handler.cpp:

    • Pin 6: Air Heater – serial command: “AAHE 1 1” – comment: “AC port 4”
    • Pin 8: Light Panel – serial command: “ALPN 1 1” – comment: “AC port 2”
    • Pin 9: Air Humidifier – serial command: “AAHU 1 1” – comment: “AC port 1”
    • Pin 14: Air Vent – serial command: “AAVE 1 1”
    • Pin 15: Air Circulation – serial command: “AACR 1 1”
    • Pin 53: Light Chamber Illumination – serial command: “ALPN 2 1”
    • Pin 52: Light Motherboard Illumination – serial command: “ALMI 1 1”

    The Food Computer basic P&ID V1.1.pdf schematic agrees with the Arduino code. The schematic says the actuator output pins should be:

    • 6: AC4 for heater
    • 8: AC2 for grow lights
    • 9: AC1 for humidifier
    • 14: Vent fan
    • 15: Circulation fan
    • 53: This is marked as “RELAY 12V Chamber lights”
    • 52: This is marked as “RELAY 12V MOTHER BOARD LIGHT”