Wouldn't using AC to power a lamp result in flickering?

[OmCheeto]

You can see it in slow motion videos:
https://www.google.de/search?q=slow+motion+light+bulb+flicker&tbm=vid

And with test gear:

The only light source I can get a (humanely) perceptible flicker from is my old LED x-mas lights.

 

[anorlunda]

The only light source I can get a (humanely) perceptible flicker from is my old LED x-mas lights.

I wonder if you were 18, if you could see the flicker. Got any teens in the house?

 

[OmCheeto]

I wonder if you were 18, if you could see the flicker. Got any teens in the house?

Nope. Just me.

ps. Haven't had a teen in my house since my housewarming party, 30 years ago, when I was about 30. Damn 25 year olds invited their younger friends, who invited their younger friends, who invited their younger friends...

<Betty Davis voice>What. a. mess... </Betty Davis voice>

I found Cheez-whiz dripping down my walls the next morning.

Never again...

 

[jeffinbath]

Indeed! Our physics class (1969/70 ?) did a 'scrap-heap challenge' demo of the system. The receiver's sensor was an OC71 transistor (with the black paint scraped off). We never got it to work over any significant distance in daylight but after dark it worked fine provided you had good optical alignment and tweaked the OC71's bias to cope with what residual background light remained. The best we managed was about 150 metres.

Yes I too affectionately remember doing an experiment just like that in the late sixties. The output light was an old 12V car side-light bulb . It needed to be fed with a constant DC bias which made it glow dim yellow and the audio input came from the wires that would have powered the 3 ohm speaker from an old valve radio. The receiver was a 6 inch diameter magnifying glass which threw a real image onto a phototransistor (OC71 type) with some amplifying circuitry feeding headphones. What staggered me was how undistorted the lower frequencies were from speech. When it came to music the higher frequencies got fuzzy but to this day I am still amazed that that car-bulb filament could cool down sufficiently in (I estimated) less than two thousands of a second so I could hear notes with frequencies of over 2000 hz. And I also was able to pick the signal up at night over 100 metres away , but at that distance keeping that tiny spot image focussed on the phototransistor became quite difficult I remember.
Actually on thinking about it more now , I must have fed the filament with audio signal from a halfwave rectifier to stop the frequency doubling effect of 2 heat-ups per cycle.

 

[jeffinbath]

I believe 60Hz was set by Nicola Tesla to reduce the cost of electrical transformers for high tension transmission lines. 50Hz transformers would be larger and more expensive. Making it higher than 60Hz reduces transformer efficiency. I think Europe chose 50Hz to avoid Tesla's patents. As far a flicker is concerned 60Hz is better than 50. Flicker is smoothed by the our optical rods and cones that have a response time curve covering about 50 milliseconds however, since this a ramp and decay curve you can still detect flicker at 20 times a second or greater. Some people are quite sensitive to the flicker of florescent lights that flicker at 120 times a second. They don't actually see the flicker but their eyes tire quickly because their iris is attempting to respond and getting mixed signals. Your iris, when you are young responds quite quickly as a measure to protect you from bright lights but with age this response slows.

I think the silicon-iron alloys used then could have worked well at twice that frequency which would have been both good news and bad news. The good news would have been smaller lighter transformers and the bad news would have been a mains hum becoming an unpopular bumble-bee buzz everywhere.

 

[anorlunda]

I think the silicon-iron alloys used then could have worked well at twice that frequency which would have been both good news and bad news. The good news would have been smaller lighter transformers and the bad news would have been a mains hum becoming an unpopular bumble-bee buzz everywhere.

The other bad news would be the series reactance of all transmission lines.

The Russians did a study in the 70's. They concluded that if everything started from scratch, 100 Hz would be the optimum. But nobody cared about the study because there is no thought of starting from scratch.

 

[AirSeeder]

https://en.wikipedia.org/wiki/Flicker_fusion_threshold

I could see flicker on Apple II monitors, back in the day, if I sat sideways to the monitor and stared straight ahead. This was with 60 Hz Canadian power. Point 5 in the Wikipedia article probably explains it.

 

[John Green]

I remember reading an article back around 1962 or 63 in Electronics Illustrated magazine detailing how to build a light communications project using an ordinary incandescent flashlight (PR-2 bulb) buck boosted by an audio amplifier, My brother and I cobbled together a home built amplifier and tested it using a telescope and a cut open transistor as the photoelectric element. we were able to transmit recognisable music several hundred feet. I was very surprised at the frequency response of the system,

 

[george brack]

I remember many years ago (60's) at a large engineering works that machine shops had to be wired in 3 phase when lit with fluorescent lights with no adjacent
light on the same phase.This was to prevent a stroboscopic effect on rotating machinery which could make a fast rotating chuck on a lathe for instance appear stationary or slow moving.

 

[Mark Harder]

I once wired a resistive optical sensor in series with a 1.5V battery and the microphone input of a cheap tape recorder to search for any interesting sounds ambient light might make. It was in a city, so no matter where I pointed the thing, all I could hear was the '60 cycle' (actually 120 Hz) hum. I thought that surely the filaments of incandescents would stay hot between the half-cycles and average out the oscillating current. But turning on the indoor lights created the loudest buzz of all. Replacing the optical sensor with a plain resistor eliminated the buzz, so the source of the hum was not currents induced by the home wiring.