test bench lighting

[EC8010]

Originally Posted by dhaen

Seems those years spent in a TV studio weren't completely wasted...

Likewise. I use guttering lined with slightly crinkled kitchen foil as a diffuse reflector for the fluorescent.

[nicoch58]

HI EC8010 I see you use High efficiency headphone

[EC8010]

Originally Posted by nicoch46

HI EC8010 I see you use High efficiency headphone

Only mono, though.

Since people were complaining about the RF noise produced by HF fluorescents and she-who-must-be-obeyed wanted better lighting for her sewing machine, I thought I'd investigate a 36W HF fluorescent before screwing it to the ceiling. The first thing I looked at was the current through the tube, which turned out to be an integrated 39kHz square wave (first waveform). Then I got the 'scope to do an FFT of that waveform to see what the harmonics were like (they go up to 570kHz). Finally, I looked at the current waveform from the mains, rather messy, but approximating to a sine wave (which is more than any audio kit does).

[jackinnj]

Originally Posted by EC8010

Only mono, though.

Since people were complaining about the RF noise produced by HF fluorescents and she-who-must-be-obeyed wanted better lighting for her sewing machine,

Still pimpin' for the Timsons then Horace?

I just call mine "obienda" -- I like gerundives.

[EC8010]

Making a good living from the Timsons

[tvrgeek]

Originally Posted by lmartine3

I added a new ultra cheap flourescent light fixture above my workbench a few days ago. It uses two T8 32W tubes.

I fired up the oscilliscope and found a horrible amount of ~45KHz noise everywhere; if I hold the scope probe up near to the light I can read 20Vpk-pk!

At a distance of 4 feet to the benchtop, it is still 100mV pp.

Is it possible to buy an electrically quiet flourescent fixture or is it just the nature of the beast?

Welcome to electronic ballasts. CFL's are worse. High quality GE ballasts are better, but still not perfect. They cost twice what you paid for the cheap fixture, but don't buzz as loud, and come on when it is cold.

I suppose at some loss of light, one could wrap the fixture in a wire cage to block some RF. Never tired it. The buzz would still drive me crazy.

I use plain old light bulbs; you know the ones they want to ban in Europe. In the winter, they are 100% efficient as you are using all the excess heat. (I can heal Al Gore wincing) LED's are not ready for prime time. Cost too much, and the ones in the local store are not as efficient as CFL! As I am not young, I need a LOT of light. A bank of PAR-60's and no problem with noise in my system. Consider it a cost of instrumentation. I use a sheet of glass to block some of the heat.

[jackinnj]

Originally Posted by tvrgeek

I use plain old light bulbs; you know the ones they want to ban in Europe. In the winter, they are 100% efficient as you are using all the excess heat. (I can heal Al Gore wincing) LED's are not ready for prime time. Cost too much, and the ones in the local store are not as efficient as CFL! As I am not young, I need a LOT of light. A bank of PAR-60's and no problem with noise in my system. Consider it a cost of instrumentation. I use a sheet of glass to block some of the heat.

Article in the New York Times -- LED Traffic Lights blamed for winter deaths -- the LED's don't heat sufficiently to melt the snow and the traffic lights become unreadable -- blamed for several deaths in the Chicago area.

[tvrgeek]

Originally Posted by jackinnj

Article in the New York Times -- LED Traffic Lights blamed for winter deaths -- the LED's don't heat sufficiently to melt the snow and the traffic lights become unreadable -- blamed for several deaths in the Chicago area.

That would never be a problem here outside DC. Nobody obeys the lights anyway!

Actually, one would need to look at the rest of the design. Plastic lens instead of glass maybe? LED's are still under 40% efficient. Lots of heat available. Glass holds the heat and is far more massive, so it would not build up while the bulb is off. A plastic lens has such low thermal mass, it could. Just a thought.

[EC8010]

Originally Posted by tvrgeek

Welcome to electronic ballasts. CCFL's are worse. High quality GE ballasts are better, but still not perfect.

Yes, I think you tend to get what you pay for. My HF fittings weren't cheap, but at least they were properly made and they don't produce as much noise as some people seem to be suffering. CCFLs draw a horrible spiky current from the mains.