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Topic: Why are incandescent bulbs blowing/burning out? How to prevent? (Read 569 times) previous topic - next topic

falexandru

In the old days there were safety fuses (wire fuses). In theory they blow before the components. Not always, in real life.

Wawa

Led with solenoid?
Back-emf?

Sounds like you didn't observe the LED's absolute max reverse voltage of 5volt.
Leo..

Doug101

Quite. That's why you always drive them with a current-limited supply.

Allan
Please explain how that works?  If a current-limited supply is used, when I need 50 LEDs lit won't the current be limited?

Grumpy_Mike

The bulbs work fine at 5.5 vdc.  They blow at around 8 volt.
But from earlier discussions they look like they will get 3V per bulb in normal use, that is 3V RMS which is a peak voltage of 4.2V. You would be better off just running them at 3V.

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The black ring in the glass makes me think they are blowing from a voltage spike and not over voltage.
There is no correlation and you can not draw that conclusion. In fact an incandescent bulb is much more resilient to voltage spikes than just about any other component. 

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I would also think they would all blow at about the same time if it were from over voltage.
That would be wrong. Any component driven over the design rating will fail at random. The more over stressed they are the more often is a failure, but they do not fail at the same time unless they are well over the rating. You are in the grey zone which is not enough to trigger instant death but too high for reliable working.

allanhurst

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The black ring in the glass makes me think they are blowing from a voltage spike and not over voltage.
In fact the very opposite. The black ring implies that the filament has partially evapourated due to over-temperature for quite a long period , which thins and weakens it.

The normal method of current limiting a LED is with a series resistor, whose value is calculated so as to limit the current to the LED's maximum current rating or below.

Allan

Doug101

So why not use a 12 c dc power supply with a voltage regulator or a buck converter?

I will get a 5vdv to power the Arduino and 5v for the lights.

INTP

Incan made to work with AC and enough in series to dissipate the expected 110-120V. I may have lost the reason why talks are of using a DC power supply and not just relaying the damn thing if control is required.

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