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Homework Help: Operational State of a Bulb

  1. Nov 25, 2017 #1
    • Please post homework questions in the homework section using the template.
    What methods other than Light Dependent Resistor incorporation are there to determine the 'bulb state'? I'm guessing it's going to include the use of another type of optoelectric component?

    Thanks
     
  2. jcsd
  3. Nov 25, 2017 #2

    Nidum

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    What does 'bulb state' mean ?
     
  4. Nov 25, 2017 #3
    I really don't know. I'm a newbie to electronic / electrical engineering.

    It's the 'operational bulb state' so I assume it's something to do with the heat generated or the wattage? The LDR determines the state by falling in resistance when the light intensity of the bulb increases, so there must be another component which acts in a similar way?

    Or will it have something to do with the workings at a smaller level such as the filament or the current?

    Thanks
     
  5. Nov 25, 2017 #4

    Nidum

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    Is this homework or a real problem to be solved or just personal interest ?
    Can you tell us in plain words what you are actually trying to find out ?
     
  6. Nov 25, 2017 #5
    Electronics homework, we've been making a circuit in class and the question simply asks 'what method, other than LDR incorporation, could the operational state of the bulb be determined?'

    Not sure how to make that plainer, it sounds like I need to know prior terminology to get the full context of the question. I can't find a definition of the operational state of a bulb anywhere, or any hints or leads on what other methods may be available
     
  7. Nov 25, 2017 #6

    Nidum

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    Sounds like you just need to measure the brightness of a bulb in a fairly basic way .

    What can you find out about :

    Electronic components which are light sensitive and which can be arranged to give a voltage or current output which varies with the intensity of light falling on them ?

    Ready made light meters ? Phone apps ?

    Older methods of measuring light intensity ?
     
  8. Nov 25, 2017 #7

    gneill

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    It might also mean that you want to find out whether or not the bulb is on or off (or perhaps defective: off when it should be on). Can you think of what, besides light output, you might detect or measure in the circuit?
     
  9. Nov 25, 2017 #8
    The circuit brief states:

    1. A light dependent resistor (LDR) is to be used to determine ambient light levels.
    2. A red light emitting diode (LED) should illuminate whenever the ambient light level is below the pre-set value.
    3. A green LED should be illuminated if the ambient light is above the predetermined level. Note, the use of two LEDs in this manner serves to indicate that power is applied to the system, as one LED will always be on.
    4. An orange LED is to flash on and off repeatedly, in the case that the ambient light level is low, and the white LED is not illuminated, i.e., it has failed. 5. Individual functional blocks of the circuit should be constructed using breadboard, and operation verified, before soldering the relevant components to circuit strip board. One example of such a component block may be the LDR and comparator light detection circuit.

    Here is the circuit on a breadboard:


    (that's not my actual circuit btw - it was a classmate's who uploaded it to FB)

    I'm not sure whether the operational bulb state refers to each of the 3 LEDs - or just the bulb?

    https://en.wikipedia.org/wiki/Optoelectronics < I'm going to look through that list to see which components are light sensitive
     
    Last edited: Nov 25, 2017
  10. Nov 26, 2017 #9

    CWatters

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    The problem statement doesn't appear to mention a light bulb just LEDs.
     
  11. Nov 26, 2017 #10
    Furthermore, the status of the light (Large white LED) is to be monitored, and if this should fail, when the lighting should in fact be on, a warning signal is to be given in the form of a flashing orange LED.

    That's another part of the brief. It's just referred to as the white LED or light.
     
  12. Nov 26, 2017 #11

    CWatters

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    This problem should really have been posted in the homework section. In that section we have a template that asks you to post the problem statement word for word. This is done for good reasons.

    Does it also say the circuit should turn the white light on if ambient levels are below the set value?

    The only sure way to know if a light is producing light is to measure or detect the light.
     
  13. Nov 27, 2017 #12
    Yes, the full brief reads:

    A controller is required to monitor the natural illumination of a sports stadium and, when the ambient light is below a pre-set level, to switch on external lighting. The system is required to be of high integrity, and various monitoring indicators are to be incorporated as specified below. Furthermore, the status of the light (Large white LED) is to be monitored, and if this should fail, when the lighting should in fact be on, a warning signal is to be given in the form of a flashing orange LED.
     
  14. Nov 27, 2017 #13

    CWatters

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    Seems straightforward enough. Can you use any components of are you limited to a list?
     
  15. Nov 27, 2017 #14
    I can use any
     
  16. Nov 27, 2017 #15

    CWatters

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    Ok now we have the full problem it's clear they mean the operational state of the white LED which is used to simulate the main lighting. The idea is to provide an amber warning indicator that is ON when the white LED is meant to be lit bit isn't because it's failed. In the real world that amber indicator might be a long way from the main lights (eg in the janitors office or even an off site location).

    There are several other devices that detect light (besides an LDR), what have you found so far?
     
  17. Nov 27, 2017 #16
    I think I may have found a few: Sensor? Thyristor? Strain gauge?

    I'm having to put this homework on hold as I've got a presentation to prepare for on Mechanical Aspects of Mechatronics, specifically a 'carousel' and I can't seem to find a basic starting page on what they are anywhere :/
     
  18. Nov 27, 2017 #17

    gneill

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    True, but for a components like lightbulbs and LEDs you can also be 99% sure that they are producing light if they are conducting current according to specification... Bulbs and LEDs tend to fail open circuit.
     
  19. Dec 1, 2017 #18
    Is it okay if I add to this thread with different questions that relate to the same circuit? (that I posted above)

    If so my next problem is finding out why a time delay is needed to show that the incandescent light had failed. I've no idea about this so any hints or pointers would be great.

    Thanks
     
  20. Dec 1, 2017 #19

    CWatters

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    How long does it take between applying power to the lamp and the light detector registering that it's producing light?
     
  21. Dec 2, 2017 #20
    I'm not sure how I'd quantify that? Would this be the 'time constant' ? I've wrote the definition as:

    'the measure of the inertia of a sensor and how fast it reacts to changes in input - the bigger the input change the slower the reaction to a change in input signal.'

    Therefore would the time delay be necessary because it helps to regulate the time constant and thus the indication of the failure?

    Last question - 'suggest a method that would improve the overall operation of the circuit?' I imagine there are many methods, each varying depending on the type of circuit and it's functionality?
     
    Last edited: Dec 2, 2017
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