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  1. Home
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  3. SI7021 boards

SI7021 boards

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  • A Offline
    A Offline
    AWI
    Hero Member
    wrote on last edited by AWI
    #8

    Another off-topic.. I use these bmp180 boards to power the low power nodes from a 4.1 volt rechargeable Li cell. The LDO is broken out on the connection

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    0
    • M m26872

      @GertSanders Link?

      A Offline
      A Offline
      AWI
      Hero Member
      wrote on last edited by AWI
      #9

      @m26872 Industrial High Precision Si7021 Humidity Sensor Module With I2C Interface link

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      0
      • G Offline
        G Offline
        GertSanders
        Hardware Contributor
        wrote on last edited by
        #10

        Without LDO, but with pull up resistors (smallest board I could find):
        http://www.aliexpress.com/item/Industrial-High-Precision-Si7021-Humidity-Sensor-with-I2C-Interface-for-Arduino/32524005324.html

        With LDO:
        http://www.aliexpress.com/item/Si7021-Industrial-High-Precision-Humidity-Sensor-with-I2C-Interface-for-Arduino/32529522264.html

        M 1 Reply Last reply
        0
        • G GertSanders

          Without LDO, but with pull up resistors (smallest board I could find):
          http://www.aliexpress.com/item/Industrial-High-Precision-Si7021-Humidity-Sensor-with-I2C-Interface-for-Arduino/32524005324.html

          With LDO:
          http://www.aliexpress.com/item/Si7021-Industrial-High-Precision-Humidity-Sensor-with-I2C-Interface-for-Arduino/32529522264.html

          M Offline
          M Offline
          m26872
          Hardware Contributor
          wrote on last edited by
          #11

          @GertSanders and @AWI Thanks!

          1 Reply Last reply
          0
          • Carl HC Offline
            Carl HC Offline
            Carl H
            wrote on last edited by
            #12

            Your plan is it to change your narrow board with SDL/SDA pad. maybe a jumper to change D2/D3 pin to SDL/SDA?

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            0
            • G Offline
              G Offline
              gloob
              wrote on last edited by
              #13

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

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              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
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                • 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.

                      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?

                        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/

                        1 Reply Last reply
                        0
                        • 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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