Procuring a new soil sensor

[aeroptl]

Hello,

I’m looking to purchase a new soil sensor for the farmbot as ours is not working. I notice that the current soil sensor provided by farmbot has 5 pins (which includes SDA and SCL).

Most soil moisture sensor has 3 pins (gnd,power,signal). For example this one https://onecall.farnell.com/dfrobot/sen0193/analog-capacitive-soil-moisture/dp/SC15117

Would this soil moisture sensor work with the farmbot? What would I lose if I switched it to a 3 pin version?

Thanks.

[Marc]

Hello @aeroptl

Which model of FarmBot do you own? You can choose to replace it with a 3 wire sensor or a 5 wire sensor. It is completely your choice, however I would suggest that you get an exact replacement and avoid any complications with other soil sensors that may not exactly work with the FarmBot.

You can order the 5 wire sensor directly from the FarmBot website and they are in stock currently as of February 14, 2025:

Genesis v1.5 Soil Moisture Sensor PCB

If you want to review the open source documentation from FarmBot on the current sensor, you can review it here:

Soil Sensor PCB

If you have an older model FarmBot and you would likely need to get an exact replacement for your soil sensor.
The three wire FarmBot soil sensor from the Genesis v1.2 (and v1.3, v1.4) design is based on the Open Source design from SparkFun.

These sensors are still manufactured and available for sale from SparkFun at this website.

SparkFun Soil Moisture Sensor (with Screw Terminals)

Here is the video that Rory created to explain how the soil sensor fits onto the universal tool mount.

Soil Sensor - FarmBot Genesis v1.2

Also, here is the video that explains the full functionality of the soil moisture sensor from SparkFun.

SparkFun Soil Moisture Sensor

Good luck and let me know how it works out.

Marc

[aeroptl]

We own the v1.6 Genesis.

I have a 3 pin soil moisture sensor, I hope that would work?

Thanks.

[aeroptl]

We connected the 3 pin sensor but unsure where the SIG connection will go. I’m not sure how the farmbot will read the sensor if SDA/SCL is not connected.

[jsimmonds]

@aeroptl

unsure where the SIG connection will go

According to
Universal Tool Mount | FarmBot Genesis Documentation
SIG should attach to UTM pin D

@aeroptl

if SDA/SCL is not connected

You can leave those I2C signals unconnected