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Homework Help: Operational State of a Bulb

  1. Dec 2, 2017 #21

    CWatters

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    Ok you didn't get the hint.

    If it takes say 1mS from the ON signal to the light being detected by the LDR. What does the bulb failure detector output during that time?
     
  2. Dec 2, 2017 #22

    CWatters

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    I've just read the question again and there is another possible reason for some sort of timer devce and that's to make the amber LED flash.
     
  3. Dec 3, 2017 #23
    The question just asks why the time delay function, in particular, is necessary to serve 'that part of the circuit' that determinines incandescent light failure.

    I don't actually know anything about 'that part of the circuit' and how it determines the failure, sorry. I'm a newbie to electronics. If I upload my circuit diagram here then that should help? I'll scan and upload it tomorrow
     
  4. Dec 3, 2017 #24

    CWatters

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    Forget how the circuit works for the moment. How do you know when a light bulb has failed?
     
  5. Dec 6, 2017 #25
    Other than it not receiving current anymore, or a fault in the circuit components I'm not sure sorry.

    Here is my circuit diagram though, would anybody be able to tell me how I should order a block diagram based on this?

    The circuit blocks are:
    Power supply, preset level of LDR, timer, operational amplifier, resistor, variable resistor, light
    dependent resistor, green led, red led, orange led, white led

    That's probably too small so I've attached the original scan PDF files

    Thanks
     

    Attached Files:

    Last edited: Dec 6, 2017
  6. Dec 6, 2017 #26

    CWatters

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    What I meant was how do you yourself (without any circuitry) know that a light bulb has failed? If you walk into a room and there is no light coming from the bulb does that always mean it's failed?
     
  7. Dec 6, 2017 #27
    Lol is that a trick question? It could be that it hasn't been turned on, been physically broken or isn't connected properly so I'd say no
     
  8. Dec 6, 2017 #28

    CWatters

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    Exactly. So failure = true when the switch is ON and the light is off. However if the light takes a fraction of a second to become bright and be detected by the LDR then the failure signal will briefly be true every time the light is turned on. This might not matter but you asked why a time delay might be required.
     
  9. Dec 6, 2017 #29
    Ahh, I see now. That's helped actually - thanks.

    Can you think of any improvements to the circuit that could be made? Up to now I've said perhaps use a different voltage which can be split more evenly across the circuit
     
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