Phototransistor and IR led

Discussion in 'General Electronics Chat' started by Chetan22339, Apr 25, 2015.

  1. Chetan22339

    Thread Starter New Member

    Mar 14, 2015
    Hello Everyone,
    I am trying to make obstacle detection kit using photo transistor and IR led.
    I got one circuit diagram from net but i dont know the use of middle terminal in its power supply of 5V DC.
    neither i know how to get it I am using dc adapter with output 5v 1A. multimeter shous it 5.12V.
    also the +ve of led is connected to -ve of power supply as per my info it should be connected to +ve.
    please correct me if I am wrong and help me to know the middle terminal how to get it.
    Thank You.
  2. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    Which middle terminal? The connection between + and - is supposed to be the output but the image you posted shows the op-amp as viewed from below.
    Yes, the LED is labelled incorrectly; it doesn't help that the "schematic" appears to have been drawn by a 4-year old.
    Last edited: Apr 25, 2015
    Chetan22339 likes this.
  3. Chetan22339

    Thread Starter New Member

    Mar 14, 2015
    thank you sir.
    the ic is lm358 whose op is pin 1 and 8 pin is vcc. but here 8 is connected to middle terminal so that confused me.i think designer interchanged 1 and 8 no pins.
  4. ian field

    Distinguished Member

    Oct 27, 2012
    It would help lazy people like me if you re-draw the layout drawing as a conventional schematic.

    You might do better by using a comparator than an Op-Amp.

    A commercial unit would most likely pulse the LED and filter the detector to accept the LED pulse rate and reject mains frequency flicker from room lighting - but that might be a thread for another day.