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
    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 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
    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

    Senior Member

    Feb 17, 2010
    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.
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Got in hurry, forgot thumb.