Current reading through multimeter

Discussion in 'Homework Help' started by inky90, Jul 31, 2017.

  1. inky90

    Thread Starter New Member

    Jul 16, 2017
    14
    0
    Hi guys,

    So basically i'm trying to read the current in my device setup connection, and as such, i have use a digital multi-meter, turn the knob to 10A with red probe to the 10A port of the multimeter and black probe to the com port of the multimeter, and lastly, i have place both red and black probes in series with my device setup. Images of rough drawn schematic as well as image of my setup is attached as shown.

    With that said, the readings from the multimeter has shown an approximate value of 0.04, which i guess is 0.04 A? so the question is why is the readings wrong? As seen from the attached image,my pololu step down regulator 5V 2.5A is attached to the device setup. So why isnt the value in the Multimeter show a value of 2.5A? Could it be due to the fuse blown? if not what is the reason?



    Side note:

    - The checking of current is learned through this youtube video

    - i cannot unscrew my multimeter because the screw is stuck inside. so instead i use the method indicated by this website to check my fuse. https://www.allaboutcircuits.com/textbook/direct-current/chpt-3/safe-meter-usage/

    - coding and setup is done according to various setup tutorials, device is working fine as intended through coding

    - The sensor that i currently have are:

    --> carbon dioxide sensor, https://www.dfrobot.com/product-1549.html
    --> adafruit ultimate gps sensor, https://www.adafruit.com/product/746
    --> TCS3200 Color Sensor, http://digitalmeans.co.uk/shop/colour_sensor-tcs3200
    --> temperature sensor, https://www.banggood.com/DS18B20-DC-5V-Digital-Temperature-Sensor-Module-For-Arduino-p-930691.html
    --> coin vibration motor, https://www.aliexpress.com/item/Bra...800295518.html?spm=2114.search0305.4.1.3blfUe
    --> RGB LED
    --> Pololu step down 5V 2.5A, https://www.sgbotic.com/index.php?dispatch=products.view&product_id=2281
    --> Lipo battery 7.4v 850 mAh
    --> arduino nano


    Setup.JPG Device with multimeter setup.JPG checking of fuse - setup.JPG checking of fuse - website.png
     
  2. simozz

    Member

    Jul 23, 2017
    99
    26
    Hello,

    2.5 A is the current that the pololu can source, and it doesn't mean that the load current will be equal to 2.5 A.
    Is this an homework ?

    simozz
     
  3. inky90

    Thread Starter New Member

    Jul 16, 2017
    14
    0
    Hi,

    so does that mean that the readout by the multimeter is showing how much current is being drawn by all of my sensors??

    btw, its my project work.
     
  4. simozz

    Member

    Jul 23, 2017
    99
    26
    Hello,

    Yes, if you connected all the sensors in series with the ammeter.

    simozz
     
  5. inky90

    Thread Starter New Member

    Jul 16, 2017
    14
    0
    Hi thanks for the clarification, erm then this brings me to another question.

    so basically previously before buying the step down regulator, i was facing current issue, this is assumed because i had directly pluck my arduino nano 5v pin to supply voltage to all my sensors, but then some of my sensors are not able to work (such as carbon dioxide not able to power up, colour sensor led lights flickering). and as such the step down regulator was implemented to address the current draw issue.

    so then the question is if my current draw is only 0.04A, then why arduino nano is not able solely supply this current to sensors instead? it should be able to supply more than 0.04A right i suppose ?
     
  6. simozz

    Member

    Jul 23, 2017
    99
    26
    Hello,

    To ensure yourself, you have to check the schematics of the Arduino nano and the datasheets of the devices it uses, (such as voltage regulator) depending to which of them you want to connect your sensors, and look for the current source limits.

    Example: if you want to connect the sensors to the output of the voltage regulator, check its datasheet.

    simozz
     
    Last edited: Jul 31, 2017
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