Need help in building a control circuit!

Discussion in 'The Projects Forum' started by manojk, Oct 2, 2010.

  1. manojk

    Thread Starter New Member

    Oct 2, 2010
    1
    0
    Hi,
    I am trying to build a circuit for a project I am working on. I have a light sensor which gives me a digital signal. I have a circuit to compare this with a threshold value and generate a 0 or 1 output. There is another mechanical switch is 1 when closed and 0 when open. Based on these two inputs (input A from the comparison and input B from the mechanical switch) I need to generate an output for a motor based on the following logic.

    A B Final Output
    1 0 1 (positive voltage)
    1 1 X (no voltage)
    0 0 X (no voltage)
    0 1 0 (negative voltage)

    This is slightly similar to the XOR gate I think except for the last combination...is there any circuit that can be built to operate on this logic?
    I don't have any knowledge about electronics (I am a mechanical engr myself) so I'd appreciate it a lot if someone can help! Thanks!
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    Something to throw knives at: A XOR takes care of condition D & E, killing power to H bridge & disabling NAND gates. C & G cause motor to turn one way, F & G cause oposite rotation.
     
  3. hspalm

    Active Member

    Feb 17, 2010
    201
    8
    I have an example circuit that uses the l293d double full H-bridge IC, which I use in many of my projects. The chip limits you to 1.2 A peak current per motor (2 motors can be driven simultaneously on one chip), The inputs from light sensor and push button must be logic level inputs.
    [​IMG]
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    Got in hurry, forgot thumb.
     
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