Switching the power source

Discussion in 'Embedded Systems and Microcontrollers' started by prabhubng, Feb 21, 2013.

  1. prabhubng

    Thread Starter New Member

    Sep 29, 2009
    I am working on a project in which I am driving a 8x8 matrix of electromagnets using 74HC595+ULN2803 combination, my problem is I should also reverse the polarity of them individually, having an H-Bridge for each output will not be an option since it's in matrix, but I am trying to have two matrix circuits one for positive and another one for negative so that I can drive selected electromagnet on decided polarity, here my problem is how can I switch between the power source from different ULN2803 legs? or is there any other way I can achieve the solution?

    Thanks in advance,
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    A schematic always helps.

    To reverse polarity you have 3 options:
    1. two coils in one magnet
    2. an H-bridge
    3. a Halfbridge and a Highside/Lowside driver.
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    If you A) are limited to a UNL2803 that switched current to ground, 2) have power to waste and Z) can use a series limiting resistor...


    The current in the resistor gets wasted but results in each coil getting driven in both directions.
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