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Little Step-U and Opto Interrupter Sensor — Parallax Forums

Little Step-U and Opto Interrupter Sensor

DavidBDavidB Posts: 2
edited 2004-10-03 22:44 in General Discussion
I'm trying to use a pair of·standard U-shaped·opto interrupter sensors as inputs for the little step-u.· Unfortunately the sensors I have run at a low state until the beam is interrupted, then they go high.· The little step u expects the input to go low when a sensor is activated.

I'm a novice when it comes to component level electronics.· Is there an easy way for me to invert the sensor output?

·

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2004-10-02 14:34
    You could use a simple transistor inverter.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas Office

    Post Edited (Jon Williams) : 10/2/2004 2:42:45 PM GMT
    inverter.jpg
    405 x 284 - 12K
  • DavidBDavidB Posts: 2
    edited 2004-10-02 15:40
    Thanks Jon. I tried this using a 3904 NPN transistor. Now when I break the beam my voltage is dropping from down to 3 volts (from 5). It isn't dropping all the way to low. I had the same problem when I tried making an inverter from a 4011 chip.

    What can I do to correct this?

    Thanks again,
    David
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2004-10-03 22:44
    You might want to drop the base resistor down to 470 ohms, just to insure saturation. That should cause the output to fall to 1 volt (spec for 3904).

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    Jon Williams
    Applications Engineer, Parallax
    Dallas Office
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