Connecting Arduino MEGA or NANO with Teros 12 Sensor

How many sensors are you wanting to connect to your Arduino board?  Do you have a Mega, or Nano, or both?  What sort of termination is on the end of your sensors?  Are you just wanting to display instantaneous sensor data on your computer or are you trying to build a logging device?

I’ve attached a screenshot from Meter Group’s Teros 12 Integrator Guide.  It shows the wiring scheme for the bare-wire version and the 3.5mm stereo plug version.  If you’ve got the sensor with the 3.5mm plug, then you’ll need to compare this diagram to whatever breakout board you’re using to match the tip, ring, and sleeve to the power, ground, and data lines.

Then you can connect those 3 lines to whichever board you’re using.  Power to Vcc (3.3v or 5v, depending on your board’s operating voltage).  Ground to Ground.  Data to a digital pin.  We usually use D7 in our example sketches because that’s the line on the Mayfly’s dedicated SDI12 Grove jack.  If you’re using a different board, you can select the pin, as long as it’s free and not used by anything else in your sketch or on-board circuitry.

The sketches you could use to communicate with the sensor can be found on our Github repo here:  https://github.com/EnviroDIY/Arduino-SDI-12

Note that Meter Group’s sensors always get shipped to you on SDI12 channel 0 (zero).  They MUST be changed to something other than 0 in order to make the sensor respond to SDI12 commands.  Otherwise, they are stuck in their default TTL serial mode, which isn’t great if you want to use more than one sensor on the same bus.  So use the example sketch named “b_address_change” to set the channel on your sensor.  Once you do this the first time, you won’t have to do it again, the sensor will remember this preference until you manually change it at a later date.

How you can use any of the other examples for the SDI12 library to query the sensor and display the data to Arduino IDE’s Serial Monitor.  If you want to integrate other hardware like a wifi board or other telemetry module, you’ll have to write your own sketches, since all our other examples are mainly written for the EnviroDIY Mayfly Data Logger board, which has a onboard microSD card socket, realtime clock, and xbee socket for compatible telemetry modules like wifi, cellular, LoRa, etc.

Did you make sure the sensor is properly wired to your Mega, (tip to 5v, sleeve to GND, and ring to data) and that the pin number in the sketch matches whatever pin number you connected the data line to?  If all the wiring is correct, then it might be an issue with the latest SDI12 library that a few people have reported.  You could try replacing all of the latest SDI12 library files you downloaded (the entire folder) and replace it with a stable legacy version (v2.1.4) from a few years ago (https://github.com/EnviroDIY/Arduino-SDI-12/tree/v2.1.4) and see if that fixes it.