2 Replies Latest reply on Aug 18, 2020 2:15 AM by yagmurozdemir

    Dark detecting circuit

    yagmurozdemir

      Hello,

       

      I had tried dark detecting circuit (3 volt battery,1 kohm resistance and 10 kohm resistance, LDR,Npn transistor) but by bonding with parallel (but)red leds but my circuit lights on in sunlight and lights on in the dark??! And when I covered Ldr sensor with my hand, I saw that there was still nothing new. I calculated inner resistance and found out the inner resistance is (approximately) 100 ohm. And first of all, I tried the same thing with one, and then two green leds with parallel bonding and I found out the inner resistance (with 1 green) is 80 ohm and 190 ohm ( with 2 parallel green led). After I used this circuit 500 ohm resistance but there was nothing new, again. The one below is what I have been talking about. I did not understand what is wrong with mine. Please help me. I am wondering what you will say.

       

      Thank you. 
      Yagmur