How do I connect a substrate probe to the Grow Sensor using the SDI-12 connector block?

To connect a compatible SDI-12 substrate probe to your Grow Sensor, follow these steps:

What you’ll need

You’ll need to purchase the SDI-12 connector kit from our website. This includes:

• 1 x SDI-12 connector block

• 1 x RJ12 cable (included)

Step-by-step setup

1

Connect the cable:

• Plug the RJ12 cable into the bottom port of your Grow Sensor.

• Plug the other end of the RJ12 cable into your SDI-12 connector block.

2

Choose your wiring method based on your probe:

• Option A: Bare wire probe

  • If your substrate probe has three bare wires at the end:

  • Use a small flathead screwdriver to open the SDI-12 connector. There are notches on either side of the case—insert the screwdriver into a notch and gently twist to pop the case open.

  • Inside the connector, you’ll find three labeled screw terminals:

    • Power (typically red or brown)

    • Ground (typically black)

    • Data (typically white or yellow)

  • Important: Most soil substrate probes list the wire colours and their corresponding functions on their product page or datasheet. Please refer to this information and double-check before wiring to ensure you connect each wire to the correct terminal.

  • Insert the wires, tighten the terminal screws, and close the case.

• Option B: Probe with a headphone jack

  • If your substrate probe has a 3.5mm headphone-style jack, you can:

    • Option 1: Cut off the jack, strip the wires, and follow the steps in Option A.

    • Option 2: Use a female headphone socket, wire that into the SDI-12 connector, and plug in the probe.

A quick note on durability

We’ve designed the SDI-12 connector to be as affordable and accessible as possible. While the case can be opened and closed, it’s not built for repeated use.

Once you’ve wired in your substrate probe correctly, we recommend keeping the connector closed permanently to avoid wear or potential damage.

Final checks

• Make sure your substrate probe is SDI-12 compatible and supported by the Grow Sensor.

• Once connected, your probe should begin reporting substrate readings in the Grow Sensor app.

• Open your grow in the app, go to Calibration settings, and select the correct substrate medium (e.g. soil, coco, rockwool) to ensure accurate readings.

Let us know if you’d like a wiring diagram or setup video — we’re happy to help!