Multiple grounds ,Multiple power supplies

Discussion in 'Analog & Mixed-Signal Design' started by Talktome, Jun 13, 2019.

  1. Talktome

    Thread Starter New Member

    Jun 13, 2019
    4
    0
    Hello all,
    I want to know the effect of connecting grounds in switching power supply with different loads and different voltage.
    In one of my design I am faced with a strange problem. Here as you can see I want to drive a 24V-5A motor. But as I switched the circuit on (my transistor is something else, A BDX53) my house fuse blew. whats wrong with it?
    [​IMG]
     
  2. Zeeus

    Member

    Apr 17, 2019
    354
    12
    Hi..Welcome to AAC

    unfortunately for you, first person to "answer" your question is a neophyte

    There's resistor from the micro-controller to base of transistor to limit current?

    "my house fuse blew" lol, really funny..
     
  3. kubeek

    Expert

    Sep 20, 2005
    5,535
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    Was if a fuse/breaker, or a RCD?
    What exactly are the power supplies?
     
  4. Talktome

    Thread Starter New Member

    Jun 13, 2019
    4
    0
    Hello all,
    Thank you for your reply.
    Yes, I have limited my transistor. it works fine with a linear (transformer) 24V adapter.
    In home, we have only fuse/breaker no RCDs.
    My power supplies are two different switching mode power supplies(24V/10A, 5V/2A).

    Is there any problem to connect ground of two power supplies? because I have heard that I should prevent connecting SMPS ground to each other when have more current( I don't know why)
     
  5. kubeek

    Expert

    Sep 20, 2005
    5,535
    1,070
    You can check the continuity between PE and the output, but my guess is they should be isolated. Not really sure why if would blow the fuse in any case.
     
  6. Talktome

    Thread Starter New Member

    Jun 13, 2019
    4
    0
    Thanks for your comment. still I am confused by this circuit behavior.
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
    18,203
    5,584
    You have used the Earth GND symbol for common, is this actually earthed or have you just used the wrong symbol for power common(s)?
    Personally I would use a logic gate Mosfet to drive the motor.
    Max.
     
    Last edited: Jun 13, 2019
  8. Talktome

    Thread Starter New Member

    Jun 13, 2019
    4
    0
    Thank you MaxHeadtoom for your comment. Yes, I have made a mistake for drawing the ground in the schematic. But in reality, I have connected my GND to -VIN of my adapter.
     
  9. KeepItSimpleStupid

    AAC Fanatic!

    Mar 4, 2014
    3,352
    610
    The power supplies may need minimum loads to function properly.
    Sense leads, if required, not connected.
    High inrush current.
    Could it be an RCD trip?
     
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