How Can We Determine the Operational State of a Bulb Without Using an LDR?

[SpiraRoam]

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

 

[Nidum]

What does 'bulb state' mean ?

 

[SpiraRoam]

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

 

[Nidum]

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 ?

 

[SpiraRoam]

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

 

[Nidum]

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 ?

 

[gneill]

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?

 

[SpiraRoam]

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

 

[CWatters]

The problem statement doesn't appear to mention a light bulb just LEDs.

 

[SpiraRoam]

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.

 

[CWatters]

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.

 

[SpiraRoam]

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.

 

[CWatters]

Seems straightforward enough. Can you use any components of are you limited to a list?

 

[SpiraRoam]

I can use any

 

[CWatters]

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

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?

 

[SpiraRoam]

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 :/

 

[gneill]

The only sure way to know if a light is producing light is to measure or detect the light.

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.

 

[SpiraRoam]

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

 

[CWatters]

How long does it take between applying power to the lamp and the light detector registering that it's producing light?

 

[SpiraRoam]

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?

 

[CWatters]

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?

 

[CWatters]

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.

 

[SpiraRoam]

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

 

[CWatters]

Forget how the circuit works for the moment. How do you know when a light bulb has failed?

 

[SpiraRoam]

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

 

[CWatters]

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?

 

[SpiraRoam]

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

 

[CWatters]

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.

 

[SpiraRoam]

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