More about the data logger

Enclosed logger

Now that the logger prototype is enclosed, it is a lot easier to use. I have a METER group 5TM soil sensor connected to it from the left side and 12V power to it from the bottom. Without a heavy enclosure, these cables will make it hard to set the logger flat and connect an adapter to it. Plus, I’ve started using Telnet to connect to it wirelessly so I don’t need an adapter to connect to it most of the time.

Here is the adapter I modified to use on the logger:

2018-07-26 22.33.25

I bought it from (Not shown on this photo) Later I had to short a resistor and a capacitor in order to actually make it work, due to the fact that the adapter was designed for Arduino boards.

Besides Telnet, I can also upload Python sketches via FTP. I later installed a couple of jumpers to easily reset the logger since I am still developing the logging script and need to reset the logger when I make changes. I’ll install a push button instead of the jumpers when I have some time.

Everything is coming along nicely. Soon I’ll start testing 4G LTE-M connectivity of the logger. 4G LTE-M has a lower bandwidth than the regular 4G LTE on smartphones so the modem would consume less power and data plans would cost less (in Megabytes instead of in Gigabytes). The Digi XBee3 LTE-M modem is rather expensive, at $100, or $150 for a dev kit. Anyway, if you are deploying the logger in a research field close to your lab/office or really don’t mind regularly visiting remote areas to collect data logs, you may skip the modem.

4 Responses to More about the data logger

  1. David da Motta Marques says:

    Think about these situations.
    1. An Arduino RS232-RS485-UART shield. Is it possible to read any equipment on the port RS485 through the port RS232?
    2. Is it possible to control (read/record) an external HD using Arduino/Raspberry? The data is coming from a PC via internet connection.
    By the way, wonderful Blog!

    • liudr says:


      Sure. I’m designing a shield board for my logger. The basic logger has enough feature for many people. The shield will have RS485 transceiver, connectors for LIDAR, sonic ranger, hardware for direct USB connection, buttons and switches to set logger in dev. mode, and possibly an LCD for simple information display.

      Using external hard drive is only possible if the drive doesn’t draw excessive power from the Raspberry pi 3B or 3B+ board. You need to manually mount the drive to a directory. Arduino won’t be able to interface with ext. drives. For stability, I would use RPI 3B(+) with externally powered USB hub. If RPI is controlling the drive, PC can’t, unless you do a 1-to-2 USB 2.0 switch so PC can switch the drive from PC side to RPI side when it is done using it. I’ve got board designs with USB 2.0 switch ICs.


  2. Andy Watson says:

    Do you have an update on this data logger? I’d really like to buy one.

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