If you light up a solar cell with a fluorescent light and observe the output on an oscilloscope, you will also see the pulsed DC as well. If you want to get a pure DC output, you will need a constant source such as a flashlight powered by batteries or natural sunlight. This is a good classroom demo.
Ωhm

 

Thanks for that Ωhm, I've never tried the solar cell test. It would be good to actually see and quantify the light ripple coming from the fluoros.

I test motors etc on my main bench and it has fluoro lights. If there is a black stripe stuck on a motor shaft I can easily set it to "strobe" speed against the 100Hz light ripple from my fluoro bench lights.

Regarding the idea that fluoros can make a machine look stationary, modern fluoros seem to have good fluorescent coatings that glow for longer and make the 100Hz ripple reasonably small.

Maybe in the "early days" of fluoro lighting the coatings were not so good and the light ripple was much higher? That would have been dangerous, especially if the guys at the time didn't understand the light was flashing on and off.

 

I'd like to see some actual reports on that. .

I don't have documented evidence of the actual incident, I would assume that in the '50's fluorescent tube coating did not have the persistence that they do now, I do know a bulletin was circulated recommending that fluorescent lighting banks in machine shops etc be spread across 3 phases to counteract the flicker.
As to the noise issue, in a busy machine shop it could be hard to detect individual spindle noise, especially where someone is wearing ear plugs, which today is virtually mandatory in many shops.
To this day, in most work place safety bulletins the hazards of stroboscopic effect of florescent's are mentioned in almost every one.
Max.

 

I'd like to see some actual reports on that. I've worked in numerous shops that only had single phase lighting and have never seen a machine spindle look remotely like it was stationary. Not to mention the noise and vibration that a running machine produces.

I've seen plenty of lathes that were smooth & quiet enough you wouldn't know they were spinning over the noise of all the other machines in the shop.

 

I'd like to see some actual reports on that. I've worked in numerous shops that only had single phase lighting and have never seen a machine spindle look remotely like it was stationary. Not to mention the noise and vibration that a running machine produces.

Here you go;
"Fluorescent lamps using a magnetic power line frequency ballast do not give out a steady light; instead, they flicker at twice the supply frequency. This results in fluctuations not only with light output but color temperature as well,[44] which may pose problems for photography and people who are sensitive to the flicker. Even among persons not sensitive to light flicker, a stroboscopic effect can be noticed, where something spinning at just the right speed may appear stationary if illuminated solely by a single fluorescent lamp. This effect is eliminated by paired lamps operating on a lead-lag ballast. Unlike a true strobe lamp, the light level drops in appreciable time and so substantial "blurring" of the moving part would be evident." From; https://en.wikipedia.org/wiki/Fluorescent_lamp


In the early days of my apprenticeship, they had some old lamp fixtures over a lathe, and at just the right speed it had the strobe effect. These lamps were the old ones that still used the 'starter cans'.

 

If you light up a solar cell with a fluorescent light and observe the output on an oscilloscope, you will also see the pulsed DC as well. If you want to get a pure DC output, you will need a constant source such as a flashlight powered by batteries or natural sunlight. This is a good classroom demo.
Ωhm

Somewhere I have a small packet of solar cells which measure about 1mm by about 3 or 4mm, they're obviously not for power generation so must be sensors.

 

Modern high efficiency flourescent lamps have an internal oscillator that drives them at around 20kHz, as do some modern LED lamps.

Both still 'blink' at this frequency.

If you are referring to CFLs,their efficiency is quite lousy!

 

And 20kHz (usually much higher) used in CFLs makes them unlikely to strobe, that equates to >1.2 million RPM the machine would need to spin at!

Also a machine would have more than 1 CFL, and they will PWM at different fequencies so would cancel strobing, and also the phosphor persistance is very long compared to a 20kHz frequency.

The PWM LED lamps will actually flash, but I can't imagine someone using a single LED lamp to illuminate their entire machine.

Do the workplace safety docs have mention of LED lamps?

 

Do the workplace safety docs have mention of LED lamps?

None that I have do, but then most are not that recent Pub's.
Max.

 

I've seen plenty of lathes that were smooth & quiet enough you wouldn't know they were spinning over the noise of all the other machines in the shop.

I agree.

But, a good Machinist knows better than to stick body parts, into a very unforgiving piece of equipment, under any circumstances.