Welcome to EnviroDIY, a community for do-it-yourself environmental science and monitoring. EnviroDIY is part of WikiWatershed, an initiative of Stroud Water Research Center designed to help people advance knowledge and stewardship of fresh water.
New to EnviroDIY? Start here

Activity

  • Profile picture of Mark

    Mark posted an update in the group Sensor Developers 5 years, 4 months ago

    Does anyone have any experience with these 24v 4-20ma depth sensors from China?
    https://www.amazon.com/4-20mA-Submersible-Transmitter-Pressure-Transducer/dp/B07F5BF248
    I have a few and they seem well constructed. We are working on integrating them with the Mayfly.
    This requires A) a 24 volt voltage source. (We are trying https://www.amazon.com/QEBIDUL-Converter-Step-down-Regulator-Stabilizer/dp/B07BTHSK8H/ref=sr_1_5?keywords=5-30+volt+dc+to+dc+converter&qid=1564408261&s=industrial&sr=1-5) and B) some input components to measure the current and protect against over voltages. Any recommendations would be appreciated.

    • Profile picture of neilh20
      neilh20 replied 5 years, 4 months ago

      Hi Mark
      Thanks for sharing – just wondering what your power supply source is. Are you solar powered, running of the LiIon battery or another source.
      Technically the spec says “Power Supply:12~36VDC” – that is nominally 24V, but actually a range. That would fit with the https://github.com/EnviroDIY/SensorModbusMaster/tree/master/hardware/Modbus-Mayfly_WingShield
      If you really need the 24V then there is a step up regulator U3V50F24

      The RS485 SOM specified in the Modbus-Mayfly_WingShield does have some protection on it – but the PCB traces are weak for the protect diodes return path to a ground. It would be simple to add a straight wire to beef up that and use the RS485 SOM .

      Have you found the manual specifying the Qidian QD-130 sensors registers to see if they are compatible one of the Maylfy RS485 sensors.

      • Profile picture of Mark
        Mark replied 5 years, 4 months ago

        Thanks for the great information. I will look into these items and get back.

      • Profile picture of Mark
        Mark replied 5 years, 4 months ago

        We are planning to be solar powered using a 2500 mAh 3.7V battery and Voltaic Systems 2W/6V solar panel

        • Profile picture of neilh20
          neilh20 replied 5 years, 4 months ago

          It sounds like the RS485 Wing Shield would work for you, probably standard voltage option but you should check it works. It does require assembly and soldering.
          I was wondering if you have the sensor manual including data protocol and what RS485 registers,

          • Profile picture of Mark
            Mark replied 5 years, 4 months ago

            No manual. Just a data sheet I can’t read

            • Profile picture of neilh20
              neilh20 replied 5 years, 4 months ago

              Hello Mark – oops I’m thinking in another dual world – my brain fart.
              The sensor is 4-20mA (i’m using that type of sensor in non-mayfly Onset U30 loggers and trying to move to Mayfly/RS485).
              The 4-20mA with excitation 12-36V is much simpler, but it is not supported directly by Mayfly.
              The excitation voltage can be done with the switched voltage booster portion of the RS485 board, and a current measurement device calibrated for the 20mA. Let me think about it and post back here
              How many are you looking for?,
              How willing/experienced are you to a) solder build boards and
              b) compile a software Mayfly build
              c) how are you looking to log the readings 1) SD card 2) WiFi to [data.envirodiy.org or..] 3) Celllar or …

            • Profile picture of Mark
              Mark replied 5 years, 4 months ago

              We are expecting to do a little soldering and working on the Mayfly sketch. The data will be sent via Wifi to our own server and to EnvironDIY

    • Profile picture of neilh20
      neilh20 replied 5 years, 4 months ago

      So to restart the thread – it can be done with RS485 wing board to generate a switched excitation voltage (from the LiIon). The voltage probably needs to be 14V+ so could be U3V50F24 to generate 24V.
      To measure the 4-20mA accurately use Adafruit INA219 with a 10ohm resistor.
      https://www.adafruit.com/product/904
      The Mayfly has the INA219 drivers, I submitted them, but they are a version of the Adafruit drivers.
      It probably makes sense to create a version of the INA219 driver as a 4-20mA sensor with switched excitation. The resistor could be an option to the driver, and for 10ohms a 20mA FullScaleReading, would be 0.2V. The INA219 measures voltage to 0.32Vs, and this would be calibrated to produce a mA measurement.
      I would recommend a 10ohm YR1B10RCC -$0.62 (accurate 0.1% with a low temperature drift 50ppm/C) https://www.digikey.com/product-detail/en/te-connectivity-passive-product/YR1B10RCC/A105944CT-ND/3477513