Q: I plan to integrate your adapters to my own controller, not a PC or raspberry pi USB port. Does your UART version adapter have all necessary resistors and no USB chip to interfere with the UART port? How do you make connection between the UART adapter and my own controller? A: Yes, all necessary resistors are in place for the UART version of the adapter and the USB chip is not on the chip to interfere. Here are some of the points: The adapter has a 6-pin header that is soldered underneath the adapter to avoid making jumper wires from being vertical, which takes extra space, or from going o ..read more

If you are measuring volumetric water content of soil with an analog sensor such as the METER group (formally Decagon) 10HS sensor, you need to convert the voltage you read from it into either VWC or dielectric constant. The manual of the sensor gives you the conversion formula. In the following video, I demonstrated how to apply the conversion formula to an analog reading: Even if you are using an SDI-12 sensor, its output may be dielectric constant instead of VWC, which needs conversion using a similar formula. I would do the conversion post data logging since I could potentially find a mor ..read more

With the help of SDI-12 USB adapter users, I constantly add more compatible sensors to my list. This time is a soil sensor: EnviroPro EP100G https://www.enviroprosoilprobes.com/ I will update my list of sensors at the end of the month. If you’ve been wondering why my demo data logger stopped showing data, good question. I started a project and set my router SSID and password for that project, forgetting my data logger needs it too. So I recently added an ethernet connection to the logger. Data are stored on the sd card, not lost, just not uploaded to thingspeak channel. Now that the logger ha ..read more

After some design and prototyping, now I have a newer version of the SDI-12 USB adapter that features larger 3.5mm terminals. The original 2.54mm terminals can accommodate 18AWG wires and the new 3.5mm terminals can accommodate 16AWG wires. I’ve never seen sensor wires that thick although you could get some really thick wires from AC adapters. The bigger terminals makes installing wires easier with the additional spacing between pins, besides they accept slightly thicker wires. The screws are also slightly bigger, making the terminals sturdier. I have to make the terminals overhang a millimete ..read more

I have recently received a few comments regarding the SDI-12 USB adapter’s terminals being too small. As a matter of fact, they are not big. They are 2.54mm (0.1″) pitch terminals. On the other hand, they can comfortable accept wires as thick as 18 AWG. I’ve rarely seen sensor cables having wires thicker than 20 AWG. Larger gauges are thinner so 18>20>22>24, AWG-wise. Also, if you have wire leads that are not tinned, you should twist the wire strands and tin the leads before inserting them into terminal blocks. Still, having wider pitch makes it easier to insert the wire leads, includ ..read more

Last year’s demo logger data stream was very successful. It demonstrated the stability of my SDI-12 adapters for long-term data logging. It ran between June and October (Minnesota is cold) for 124 days. Except for occasional power outage at my house, the logger was running without a problem using the 1.5.0 logging script. This year I updated the logging script to 1.6.0 and have got a CCTV power bank to use as a backup power supply in case of power outage. Here is a battery similar to mine that is sold on amazon.com: The nice thing about this battery is that it gets charged via the 12V power b ..read more

I recently got a request to add bidirectional transceivers to my SDI-12 USB adapters to handle very long SDI-12 bus wires (result of long wires for each sensor and a large number of sensors). Currently a couple of these adapters are being tested by one customer who requested this feature but I am pretty confident with its functions and will conduct my own testing with long wires. If this is what you have in mind, I have a handful of them I’ve built as prototypes. You can go ahead and purchase a regular SDI-12 USB adapter and request one with a transceiver. I don’t have a lot of them so I can o ..read more

In case you wish to integrate the SDI-12 USB adapter into your existing Python script, here I provide a simple script to demonstrate how to get data. You can also use this script as a spring board to establish serial port communication in Python for anything else, such as talking to Arduino. The goal is to not complicate things with the full-feature data logger script. You’ll see that the actual data logging only needs a few lines of code: Simple sensor detection and reading (2018-12-03) This script demonstrates how to integrate SDI-12 sensors into your existing Python data logging system by p ..read more

I conducted a long run (5 months) on an SDI-12 sensor with a raspberry pi zero in the months of June to October to test the long-term stability of my data logging solution. I was using a regular SDI-12 USB adapter, a Decagon/METER Group soil sensor model 5TM with dielectric constant and temperature sensors and I buried it in my back yard. Over 100K data points later, the ground was freezing and I unearthed my sensor and stopped the feed. Here is an overview of the data feed. Please click the plot to see a full-size screen grab. The top plot is dielectric constant. Each spike represents a major ..read more

Q: I plan to integrate your adapters to my own controller, not a PC or raspberry pi USB port. Does your UART version adapter have all necessary resistors and no USB chip to interfere with the UART port? How do you make connection between the UART adapter and my own controller? A: Yes, all necessary resistors are in place for the UART version of the adapter and the USB chip is not on the chip to interfere. Here are some of the points: The adapter has a 6-pin header that is soldered underneath the adapter to avoid making jumper wires from being vertical, which takes extra space, or from going o ..read more