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  1. Home
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  3. SI7021 boards

SI7021 boards

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  • G Offline
    G Offline
    gloob
    wrote on last edited by
    #13

    It`s a mess that the pinout of both modules is different.

    1 Reply Last reply
    0
    • G Offline
      G Offline
      GertSanders
      Hardware Contributor
      wrote on last edited by
      #14

      @Carl-H it's a possibility. No plans yet, other projects ongoing.

      1 Reply Last reply
      0
      • F Offline
        F Offline
        fleinze
        wrote on last edited by
        #15

        I just received some si7021 boards from china. They are with LDO and level shifter, similar to
        http://www.aliexpress.com/item/Si7021-Industrial-High-Precision-Humidity-Sensor-with-I2C-Interface-for-Arduino/32529522264.html
        (the original offer went offline, it was from a reseller named "home boutique", no idea why they sold this item)
        If I use them with a battery node, is it sufficient to remove (and short-cut) the LDO or do I need to remove the level shifter too?

        A ? M 3 Replies Last reply
        0
        • F fleinze

          I just received some si7021 boards from china. They are with LDO and level shifter, similar to
          http://www.aliexpress.com/item/Si7021-Industrial-High-Precision-Humidity-Sensor-with-I2C-Interface-for-Arduino/32529522264.html
          (the original offer went offline, it was from a reseller named "home boutique", no idea why they sold this item)
          If I use them with a battery node, is it sufficient to remove (and short-cut) the LDO or do I need to remove the level shifter too?

          A Offline
          A Offline
          AWI
          Hero Member
          wrote on last edited by
          #16

          @fleinze I would suggest to leave these as they are and measure the consumption. Removing the LDO didn't give me a noticeable difference. It could depend on the board however.

          1 Reply Last reply
          0
          • F fleinze

            I just received some si7021 boards from china. They are with LDO and level shifter, similar to
            http://www.aliexpress.com/item/Si7021-Industrial-High-Precision-Humidity-Sensor-with-I2C-Interface-for-Arduino/32529522264.html
            (the original offer went offline, it was from a reseller named "home boutique", no idea why they sold this item)
            If I use them with a battery node, is it sufficient to remove (and short-cut) the LDO or do I need to remove the level shifter too?

            ? Offline
            ? Offline
            A Former User
            wrote on last edited by
            #17

            @fleinze I am using ATmega328 with 1Mhz and with LDO i have 15uA in standby mode. I have removed the LDO and measured 8uA. You should try it yourself.

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            • F fleinze

              I just received some si7021 boards from china. They are with LDO and level shifter, similar to
              http://www.aliexpress.com/item/Si7021-Industrial-High-Precision-Humidity-Sensor-with-I2C-Interface-for-Arduino/32529522264.html
              (the original offer went offline, it was from a reseller named "home boutique", no idea why they sold this item)
              If I use them with a battery node, is it sufficient to remove (and short-cut) the LDO or do I need to remove the level shifter too?

              M Offline
              M Offline
              m26872
              Hardware Contributor
              wrote on last edited by
              #18

              @fleinze I wrote a few words about it over here http://forum.mysensors.org/topic/3049/slim-node-si7021-sensor-example/

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              • F Offline
                F Offline
                fleinze
                wrote on last edited by fleinze
                #19

                @m26872 @kenci @AWI Thank you very much for your answers!
                I will go for removing the LDO but letting the level-shifter in place, because it is a pain in the ass to bypass the levelshifter.

                Bypassing the desoldered LDO is very easy. Just connect the following point on the resistor-array:
                0_1455974189828_gy21.jpg

                A 1 Reply Last reply
                0
                • F fleinze

                  @m26872 @kenci @AWI Thank you very much for your answers!
                  I will go for removing the LDO but letting the level-shifter in place, because it is a pain in the ass to bypass the levelshifter.

                  Bypassing the desoldered LDO is very easy. Just connect the following point on the resistor-array:
                  0_1455974189828_gy21.jpg

                  A Offline
                  A Offline
                  AWI
                  Hero Member
                  wrote on last edited by
                  #20

                  @fleinze The 662k on this board has a typical drop-out of 250mV and power consumption of only 1uA... and takes care of a stable power supply. I doubt if there is any advantage in bridging or removing the LDO.

                  662k
                  0_1456149818998_upload-5b22a252-988a-4acd-b4d8-15be0500a58c

                  si7021
                  0_1456149758981_upload-6a1d2eb3-c0c8-4556-a701-7d2e5db8608c

                  G 1 Reply Last reply
                  0
                  • A AWI

                    @fleinze The 662k on this board has a typical drop-out of 250mV and power consumption of only 1uA... and takes care of a stable power supply. I doubt if there is any advantage in bridging or removing the LDO.

                    662k
                    0_1456149818998_upload-5b22a252-988a-4acd-b4d8-15be0500a58c

                    si7021
                    0_1456149758981_upload-6a1d2eb3-c0c8-4556-a701-7d2e5db8608c

                    G Offline
                    G Offline
                    GertSanders
                    Hardware Contributor
                    wrote on last edited by
                    #21

                    @AWI What happens when the input voltage drops below 3.1V ? It seems the output voltage just follows the input voltage minus the dropout. I have not measured this yet, but I'm assuming this, since i have nodes working below 3.1V and sending temperature and humidity readings.

                    A 1 Reply Last reply
                    0
                    • G GertSanders

                      @AWI What happens when the input voltage drops below 3.1V ? It seems the output voltage just follows the input voltage minus the dropout. I have not measured this yet, but I'm assuming this, since i have nodes working below 3.1V and sending temperature and humidity readings.

                      A Offline
                      A Offline
                      AWI
                      Hero Member
                      wrote on last edited by AWI
                      #22

                      @GertSanders No conclusive reading from the datasheet. I will do some measurements later. ..

                      0_1456219785462_upload-af85eb98-f577-4011-96e9-ef35b5ef97bb

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                      0

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