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Help with Optical Switch

Discussion in 'General Electronics Discussion' started by Bhedstrom, Jan 11, 2013.

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  1. Bhedstrom

    Bhedstrom

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    Jan 11, 2013
    Ok, I hate to ask but I need help. I am building a pickup winder for making custom guitar pickups and need to add a trigger to an electronic counter. I have these optical switch and this is a direct link to the data sheet

    I have a 12v power supply in the winder to power the counter. I think I need a 220ohm 1 watt resistor for the emitter side of the switch. The data sheet is confusing me for some reason. From what I can tell the Forward voltage is 1.3v and the forward current is 50ma. Is this correct?

    Also, how do I connect the ouptut transistor to my counter? Does it act as a simple switch or do I need to add other components to this side of the optical switch? I thought I could supply 12v to the white lead which I think is the transistor emitter and connect the green wire to the pulse input of the counter. Could someone please let me know if this is correct?

    Thanks!
    Bryan
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,522
    2,654
    Nov 17, 2011
    Welcome to the forum.

    50mA is the max. current. Operating current for the LED is 20mA (data sheet page 7). Therefore yourresistor should be (12-1.6)V/20mA=520 Ohm (use 511 Ohm from the standard series). The power is I²*R=208mW, so a 1/4W resistor is o.k.

    The output transistor alone is not very useful. Connect the emitter to GND. Connect a resistor (e.g. 1kOhm) from collector to Vcc. Tap the collector-resostor junction for the counter signal. Whenever the slot of the optical component is unblocked, light shines on the transistor and the output will be low (~0V).
    When the slot is blocked, the light to the transistor is interrupted. The transistor will turn off and the output will go to Vcc.
    Select Vcc such that it is compatible with the input of your counter (porbably only 5V, not 12V).

    Harald
     
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