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MS One-Wire Power

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    • 2022-07-14 at 10:51 PM #17149
      KBR Kings River
      Participant

        To connect 3 pin One-Wire temperature senor I had wanted to use the Grove D10-11 port.

        Power to 3.3V_SW

        Sensor to D10

        Ground to GND

        Using the ModularSensors Code   MaximDS18 ds18(OneWirePower, OneWireBus);    MaximDS18 “(22, 10);

        Using the switch power this I don’t get a reading -9999.00  however if I switch the power pin to H2 pin 1  “always on power 3.3V” I get a correct temperature value.

        I had originally used the Example_05_Mayfly_DS18B20temp.ino
        //github.com/EnviroDIY/LearnEnviroDIYcode/tree/master/Part1-sketches/Example_05_Mayfly_DS18B20temp

        In this code the power is the  switchedPower = 22 but the switched Power is always on.

        Something with the SwitchedPower On/Off  is causing bad reading?
        I have a Sonar and a few Analog devices also using the Switched Power and they are working ?

        Do I need to make any changes to the ModularSensors/src/sensors/  MaximDS18.cpp  –  MaximDS18.h  ?
        and I really don’t how to incorporation the changed library into  VS Code PlatformIO ini file    lib_deps =   envirodiy/EnviroDIY_ModularSensors

        Thanks Ron

      • 2022-07-17 at 6:07 PM #17152
        Shannon Hicks
        Moderator

          Onewire sensors like the DS18b20 don’t like to have their bus power cycled on and off.   Back when I last experimented with them (with a different sketch not related to ModularSensors), if you’ve got the sensor connected to the switched power supply, you had to do “DSsensors.begin();” each time the logger woke and powered up the switched power bus.  Only then will the DS18b20 be seen by the Mayfly.  So I just put that command in the loop right after the Mayfly wakes up from sleep.

          The easy solution to this is to just connect the DS18b20 to the Mayfly’s D5-6 Grove jack and put the power-select jumper to “3.3v const”(it’s default position) that way the Onewire sensor is constantly powered and won’t “disappear” after the pin 22 switched power is cycled.  Having a constantly powered Grove jack for I2C and Onewire peripherals is exactly why I designed the Mayfly’s D5-6 jack power selection options.

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