Create External long term and Efficient Power Supply for Wireless Temperature Sensor

Discussion in 'Power Electronics' started by ronbo76, Nov 10, 2018.

  1. ronbo76

    Thread Starter New Member

    Apr 2, 2018
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    0
    I want to make the power supply in which need to send the output of 20mA current which is provided to my wireless temperature sensor, I am using 9v battery cell.

    I don't have much good knowledge about current amplification so I was thinking to start with Transistor circuit for current amplification.
    I need some advice about how much minimum input current, I have to give to the transistor via 9v DC battery so that I will be able to achieve around 20mA output.

    Any circuit suggestion or any theoretical explanation will be a great help to me.

    Note: The sensor also has the standard version in which they provide the external power for input, which I am using with my storage containers.
     
  2. danadak

    Distinguished Member

    Mar 10, 2018
    2,810
    605
    Not clear what you are trying to do.

    Can you hand draw a simple block diagram of sources and loads,
    labeled with voltage and current ?


    Regards, Dana.
     
  3. ericgibbs

    Moderator

    Jan 29, 2010
    7,567
    1,521
    hi robo,
    The datasheet for the wireless temperature sensor states
    Up to 500,000 Transmissions from 2 AA Batteries

    E
     
  4. ScottWang

    Moderator

    Aug 23, 2012
    6,624
    1,022
    The power info shown in your links as Powered by just 2 AA batteries, that is about 3V, but you using 9V battery, do you have more info as V/I about the sensor and the voltage range?
     
  5. ronbo76

    Thread Starter New Member

    Apr 2, 2018
    20
    0
    Hi,
    First of all thanks for the reply, In this Wireless Temperature sensor, 2 AA batteries are used

    but-but-but!!

    They also give the optional external power adapter option, And I want to design the 9v battery power source to connect it with optional power and send minimum current input which amplified and send the 20mA output to the circuit they are using. I just need some basic suggestion is it possible?
    Any useful circuit design and leads to make this kind of power circuit work will be much helpful.
     
  6. ericgibbs

    Moderator

    Jan 29, 2010
    7,567
    1,521
    Morning ronbo,
    The minimum 20mA current value on its own does not give enough information for us to make a helpful suggestion.
    Is there a voltage range stated ? ie: 6Vdc thru 9Vdc
    E
     
  7. ScottWang

    Moderator

    Aug 23, 2012
    6,624
    1,022
    The easy way is that you can use a 78L33 (3.3V/100mA) voltage regulator and two schottky diodes to connected 78L33 and the 2 AA batteries together, you can buy an adapter like 9V/100mA, the Vf (forward voltage) of Schottky diode about 0.3~0.4V, I can't make sure the working voltage range of sensor, if the sensor could working lower than 3V then the circuit shown below will be works, normally you don't have to limits the current, the sensor will be draw only what it needed.

    78L33 and 2AABatteries auto switching_ScottWang.png
     
  8. ronbo76

    Thread Starter New Member

    Apr 2, 2018
    20
    0
    Hi, Thnks for your circuit suggestion,
    Can I also use ULN2803 for current amplification?

    I have used it with 7 Segment Display and it was working fine with it. So can I use the same IC, For my circuit to draw more current from the power supply?
     
  9. ScottWang

    Moderator

    Aug 23, 2012
    6,624
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    What's the load (V/I) for ULN2803 (500 mA)?
    Maybe you can use 2SC1384(1A) to drive the load.
     
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