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# faulty Lights(AC) Detector

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#### ranariaz

##### New Member
We have a project to make on Air Field Lighting System. Different AC lights works on runway for different causes. These all lights are connected in series and isolated by isolation transformers. These are very high intensity and very powerful lights. We are also making faulty lights(AC) detection circuit in this project. i want to know if u guys have any idea to share about faulty light detection circuit of AC lights that it helps me in my project.

#### crutschow

##### Well-Known Member
I assume you mean the lights are connected in parallel(?). If connected in series, when one burns out they all quit, like the old Christmas tree light strings. You wouldn't want that for Air Field lights.

To detect if one light burns out in a parallel string, you could monitor the current. A light burning out would cause a sudden decrease in current. A current transformer can be used to isolate and monitor this current. Rectify the transformer output and connect to a voltage comparator to detect when the current drops below the normal value.

#### tcmtech

##### Banned
You could just walk out and look after dark.
A good spot of colored chalk will stay put for a few days and that would allow the fix it guys to find it in the day time.

I know its low tech but it wont break down and it has 100% accuracy!

#### audioguru

##### Well-Known Member
If the airfield has a technician who doesn't know the difference between series and parallel then I would want to know where so I can keep away from there.

#### ranariaz

##### New Member
dear the light of air fields are connected in series but with isolation transformer. so it doesnt matter that if one light is burn than all the circuit is disconneted. This transformer is same promary and secondary wiring it is only used to isolate the ckt that the ckt will no quiet if one light is burn.

#### Mike_2545

##### Super Moderator
dear the light of air fields are connected in series but with isolation transformer. so it doesnt matter that if one light is burn than all the circuit is disconneted. This transformer is same promary and secondary wiring it is only used to isolate the ckt that the ckt will no quiet if one light is burn.

It does not matter if you use an Isolation transformer or not, If one light goes out in a series circuit they will all go out, unless there is a shunt that kicks in to bridge the break in the circuit.

##### New Member
You could just walk out and look after dark.

Have to admit as solutions go the simplest are often the best, especially as part of runway safety involves daily checks for debris along the length of it. Bits fall off aircraft more often than you would like to think.

Also worth mentioning runway lights at large airports have to be cleaned regulary because aircraft tyres use soft rubber compounds like formula one cars for extra grip under braking the downside being they shed molten rubber as fine droplets all over the tarmac and lights.

So these lights do get a lot of close human attention already.

Electronic monitoring and reporting of bulb failure would be adding an extra layer of safety I suppose, humans do make silly mistakes. Lamp On , lamp OFF.. is my face warm , are my retinas buring ....

Measuring total current load would tell you if one or more bulbs had blown (depending upon if you wire them using series or parrallel) then somebody could look out the window..

Real world problems are never just about Electronic Engineering
but rather Electronics AND Engineering.

#### Diver300

##### Well-Known Member
Runway lights are run as a series circuit, with each lamp run on a transformer.

The primary winding of the transformer provided the path for the other lamps if one bulb blows. I guess that the transformer feeding a blown bulb saturates and gets hot. It might be possible to detect the transformer saturation to indicate a blown bulb.

Siemens claim to have done something like that. Runway Lighting

#### jakeselectronics

##### Member
what like this?

I can see one MAJOR benefit from doing this...
As the length of the run way can be very long, runing lights that draw a lot of current, the cables would have to be quite big. \$ding ding ding. money for copper.
Plus when excess current is drawn you get voltage drop,

So by running transformers in series, they run HV (well maybe not HV, but a higher voltage)
When a globe pops though, not all pop.
By doing this you can Up the Voltage, therefore lower current, therefore MUCH smaller cables. Less costly, and little voltage drop problems (because of low current)
And the transformers ratio then converts the higher voltage down, therefore more current to the light.

I am only guessing here.....
But it sort of makes sense.

#### ranariaz

##### New Member
yes the same schamatic that uploaded above. it is correct

#### ranariaz

##### New Member
The schametic drawn above is correct.

These lights are also very expensive the copper and the cable are used wid repect to lights. By using HV and stepping down to LV. It need extra maintance, size. The transformer wil used for that puprose is 3 or 4 times heavy and large with iso.. transformer. I think it is not a relaible method.

Tell me any idea in detail about faulty light detection

#### ranariaz

##### New Member
"To detect if one light burns out in a parallel string, you could monitor the current. A light burning out would cause a sudden decrease in current. A current transformer can be used to isolate and monitor this current. Rectify the transformer output and connect to a voltage comparator to detect when the current drops below the normal value"

CAN ANY ONE EXPLAIN THIS IN DETAIL M BY THE HELP OF SCHEMATIC.

#### Boncuk

##### New Member
Hi ranariaz,

here is a schematic. It uses a current transformer being made of a toroidal core inductor as normally used in dimmer circuits. Use three to four windings of sufficient diameter (for lowest voltage drop) to make the primary winding being connected in series with the lamp.

The two stage amplifier following the tranformer has a total amplification of about 1,000:1, adjustable via P1. The amplified AC is then rectified and charges output capacitor C3 with a time constant of 50ms.

As long as the lamp is working properly the output voltage is high. If the lamp circuit is interrupted is goes low.

Refer to the photo to make a current transformer. The black cable is connected in series with the lamp.

Boncuk

#### Attachments

• current-transformer.gif
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• LIGHT-MONITOR.gif
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#### Diver300

##### Well-Known Member
That is a neat way of making a current transformer. In the circuit, I think the diodes are the wrong way round.

However, as it is a current transformer, the load impedance on it should be low, or it will saturate and heat up. I realise that it is probably not a big issue on such a small transformer, but keeping load impedance low is common practice on current transformers.

It is also easier to get the correct calibration. At the moment you have transformer with a current input and a voltage output, so the ratio depends on the inductance (and frequency) as well as the turns ratio. If the output is current, the current ratio only depends on the turns ratio.

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