Attaching a Campbell Scientific OBS3+ turbidity sensor to Mayfly

We currently don’t sell the screw terminal adapter, but I’m working on getting them to Amazon this week. I’ll post an update here when they are available.

For each supported sensor in the Modular Library there’s an extensive wiki. I haven’t used that sensor, but the OBS3+ wiki (https://github.com/EnviroDIY/ModularSensors/wiki/Campbell-OBS3) says that it’s an analog communication and here are the wire color details:
“The power supply is connected to the red wire, low range output comes from the blue wire, high range output comes from the white wire, and the black, green, and silver/unshielded wires should all be connected to ground.”

So this basically means that the low range goes to one analog pin and the high goes to to another analog pin, such as AA0 and AA1 on the Mayfly. I assume there’s a place in your sketch to define which pin is low and which is high. Then red is voltage and the other three all connect to the ground. You could do this through a Grove port (with a 4-screw terminal), or the analog header rail.

The OBS sensor comes a with bare-wire cable with 6 leads. Three of them need to be connected to the Mayfly ground (sensor power ground, sensor signal ground, and sensor shield). Then the 3 other sensor wires get connected to the remaining 3 pins of a Grove terminal (note, you have to use one of the two Aux A/D Grove inputs only). Seeedstudio make a 4-pin screw terminal Grove board, but the hard part is getting all 3 ground wires into one tiny screw terminal, so I designed the custom 6-pin screw terminal board because it has two additional ground terminals. If you didn’t want to use a screw terminal, you could just take a Grove cable, cut it in half, strip the ends, and solder them together, making sure you get the power and two analog signal wires connected to the right wires, and solder all 3 sensor ground wires to the single Grove cable ground wire. But the Grove cables have a very small gage wire in them which is hard to solder properly, and will likely break under frequent flexing unless you properly protect it. And if you do all of this cable soldering outside of the Pelican case, it’s impossible to cram the Grove connector through the cable gland in the bottom of the case.

So the easiest thing is to just run the 6 bare wires into the bottom of the Pelican case and use the 6-pin screw terminal. If you can wait about a week, they’ll be available in the Amazon store for purchase.

The Grove 6-pin screw terminal adapter board is now available on Amazon: https://www.amazon.com/dp/B07PVKQVH8