A project i tried doing sometime back

Discussion in 'General Electronics Chat' started by haditya, Mar 28, 2004.

  1. haditya

    Thread Starter Senior Member

    Jan 19, 2004
    220
    0
    hi
    here is a circuit diagram of a project i tried doing some time back ..which didnt work as its supposed to (rather didnt work at all). i am posting the diagram as i found it in some website.

    i am posting a document which contains the diagrams along with some notes. I am not a expert but my guess is that there are some flaws with the circuit diagram.

    A few points which i noted are:-
    1. some of the wires shown in the circuit diagram are criss-cross over others. there is no indication of a connection of 2 wires with the aid of a "solid dot".
    2. In the emitter circuit consisting of IC 555 the terminal 3 (output terminal) is connected to +Vcc(suplly voltage) through a 5k resistor :wacko: . this completely baffles me.
    3. and what is an IR detector. I didnt get the sharp IR module and instead used a Photodiode. Is that why the project failed???
    i need to get the authenticity of the diagram verified. i thought some of your knowledge may help and you may be able to provide some corrections.

    thank you
     
  2. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    1,437
    1
    hi,

    have just seen the circuit drawing of the ir sender. well all criss crossing lines have to be connected if that is part of your problem. the other one is the pull up resistor at pin 3 of the 555, the resistor value is 10 ohms not 5k. it also helps in the resetting of the timer. your other problem is you should have use a match pair ir sender/detector.

    you can try to revive that project by checking on the interconnections and use the appropiate ir sender/detector. don't worry about the frequency that was designed at 30khz. the usual frequency is 38 - 40 khz, you can also do that it is just a matter of computing at what frequency your 555 will operate.
     
  3. haditya

    Thread Starter Senior Member

    Jan 19, 2004
    220
    0
    ok.. sorry about that 5k/100 ohm error.
    what exactly is a match pair ir sender detector??
    i quite didnt get the part of reseting the timer . some more input on that will be appriciated.
    thanks
     
  4. qtc3

    New Member

    Apr 24, 2004
    5
    0
    >1. some of the wires shown in the circuit diagram are criss-cross over others. there is >no indication of a connection of 2 wires with the aid of a "solid dot".
    >2. In the emitter circuit consisting of IC 555 the terminal 3 (output terminal) is >connected to +Vcc(suplly voltage) through a 5k resistor [wacko.gif] . this completely >baffles me.
    >3. and what is an IR detector. I didnt get the sharp IR module and instead used a >Photodiode. Is that why the project failed???

    1) I dont see any wires crossing that shouldn't be connected.

    2) From my glance at the schematic, I'd say that 100 ohm resistor is to limit current to the diode. I figure about 1.5V is dropped across the diode, so 3.5V goes across the resistor, and since I = V/R, we are supplying 35mA to the diode.

    3) I think the photodiode could be a problem, since it detects visible light. If the room is lighted, the diode presents a constant path to ground. The way I think this detector works is by presenting a changing path to ground through the IR detector, supplying a changing signal to the op-amp which amplifies the difference between inputs. The neat thing (to me), is that because it goes into the inverting output, and the IR detector effectively shorts current when it detects light, you get a non-inverted signal. Anyway, I'd use an IR detector.

    Take this with a grain of salt, as I am a still a student and in no way an expert.
     
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