Incandescent light bulbs (tungsten) popping taking out fuse in fuse box?

[bernardgreen]

Incandescent lamps do create a strobe effect which was useful for checking / adjusting the speed of wind up gramophone turntables.

Small ( torch bulb ) sized lamps could be used to transmit speech modulated light beams to a receiver some tens of yards away

 

[JohnW2]

Incandescent lamps do create a strobe effect which was useful for checking / adjusting the speed of wind up gramophone turntables.

True, but I'm pretty sure you will agree that the effect is very much less than with a fluorescent (with inductive 'ballast'). After all,m there is a definite to how much cooling (hence reduction in light output) of the filament can happen in 10 - 20 milliseconds.

Small ( torch bulb ) sized lamps could be used to transmit speech modulated light beams to a receiver some tens of yards away

Indeed - I've done that in my time (and for digital data as well as speech). However, again, the magnitude of the modulation would be a very small proportion of the magnitude of the 'carrier'.

Kind Regards, John

 

[bernardgreen]

a very small proportion of the magnitude of the 'carrier'.

Yes it is; but a strong carrier with a bit of modulation is much easier to spot from a distance and line up on.

 

[UseLeSsDiYr]

Yes, it's 'normal'.

Many/most mains-powered LEDs will have at least some 50 Hz or 100 Hz flicker (light intensity varying 50 or 100 times per second). That's usually not noticeable but will result in a 'stroboscopic' effect when viewing an illuminated rapidly moving object. Fluorescent tubes with 'old-fashioned' (not 'electronic') 'ballasts' in their fittings are much worse in that respect - and can be dangerous in workshops etc. because rapidly rotating tools/blades etc. can appear to be almost stationary.

Extra low voltage (e.g. 12V) LEDs will usually have an external power supply which the results in any 'flicker' being at thousands of times per second (not 50 or 100), so this effect is unlikely to be seen. Similarly with fluorescent tubes using modern 'electronic ballasts', for the same reasons.

This wasn't an issue with traditional (incandescent/filament) bulbs since, although the heating (by electricity) fluctuated 100 times per second, the filament essentially remained red/white hot 'continuously'.

Kind Regards, John

Thanks for the info John.

That's interesting, and as you're aware, I'm fresh to all this and much to learn!

Just I haven't noticed with incandescent and CFL bulbs. Switching to branded LEDs such as Osram or Phillips will not help by the sound of it?

It seems an inherent issue with LEDs?

 

[bernardgreen]

It seems an inherent issue with LEDs?

To be pedantic the problem is in the way the LED element is supplied with the current required to illuminate.

Using DC from a battery with a resistor in series with an LED element to set the amount of current flowing through the LED element will provide steady flicker free illumination.

Using DC from a battery to feed a LED lamp ( LED element and integral driver ) with an electronic driver ( not a resister ) may or may not provide flicker free illumination.

Converting 230 Volts AC into a controlled DC current for the LED element(s) opens up a can of worms.

 

[JohnW2]

Yes it is; but a strong carrier with a bit of modulation is much easier to spot from a distance and line up on.

Sort-of - although "100% modulation", if were it possible (which it clearly isn't in the situation we're discussing), would presumably result in an average intensity of around 50% of that of such a 'strong carrier' - hence not too difficult to 'spot from a difference'.

In the case of modulating the light with audio, the extent modulation (in terms of light intensity) will presumably be very small, since the periods during which 'filament cooling' have to occur is often going to be well under 1 ms.

Kind Regards, John

 

[JohnW2]

Thanks for the info John. That's interesting, and as you're aware, I'm fresh to all this and much to learn! Just I haven't noticed with incandescent and CFL bulbs. Switching to branded LEDs such as Osram or Phillips will not help by the sound of it?

No, it's essentially nothing to do with the make/quality of the LED (although more expensive makes have the potential to have been designed/engineered so as to reduce the problem).

It seems an inherent issue with LEDs?

As bernard has explained, it's really to do with the nature of the electricity supplied (by some sort of power supply) to the LED element (the bit that produces the light).

As bernard has explained, if the supply were DC (as from a battery), then there would be no such issues with any sort of lamp/bulb (LED, incandescent/filament or even fluorescent) - the issue therefore is how close to DC (how 'clean') is the electricity supplied to the lamp/bulb (which is derived from 230V AC) .

Kind Regards, John