test bench lighting

[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?

[star882]

If you can afford it, use LEDs. Halogen is another option, but it's much less efficient.

Also try adding a metal window screen over the cover and grounding it.

[Juergen Knoop]

leds beating 64W flourescent tubes? You are kidding!
Regards

[MJL21193]

Originally Posted by Juergen Knoop

leds beating 64W flourescent tubes? You are kidding!
Regards

I have an 18V Li-ion battery drill that has 2 high intensity LEDs as task lighting. I imagine an array of 30-40 would cast a good shadow!

[Richard Ellis]

Luxo lamps with incandescents...At least three for variable point sources, four is best. Trying to use flourescents for benchwork for me is all wrong. The color is unbearable, the buzzing is annoying....and as you yourself has discovered, are electrically noisy. The Eco-friendly argument is false as flourescents require more "environmental damage" to produce & dispose.

__________________________________________________ __________-Rick....

[Juergen Knoop]

my T5 workbench lighting has a efficiency of about 100lm/W.
A good T8 tube reaches about 85lm/W.
Regards

[lmartine3]

Originally Posted by Richard Ellis

Luxo lamps with incandescents...At least three for variable point sources, four is best. Trying to use flourescents for benchwork for me is all wrong. The color is unbearable, the buzzing is annoying....and as you yourself has discovered, are electrically noisy. The Eco-friendly argument is false as flourescents require more "environmental damage" to produce & dispose.

__________________________________________________ __________-Rick....

So any recommendation on where to place point sources like incandescents? All in a row to match a fl. tube, or is there a better arrangement? Perhaps I will have to try some out.

[Juergen Knoop]

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?

I had to wrap the probe around the lighting fixture to get a 10mV HF noise on the scope. The noise is completely gone at app. 40cm distance.
Maybe you can modify your lamp and use a conventional ballast?
Regards

[Elvee]

Originally Posted by Juergen Knoop

I had to wrap the probe around the lighting fixture to get a 10mV HF noise on the scope. The noise is completely gone at app. 40cm distance.
Maybe you can modify your lamp and use a conventional ballast?
Regards

I have a conventional ceiling fixture, approx. 2m away from my work area, and sensitive circuits can pick up the 50Hz magnetic hum leaked by the ballasts.
It took me a moment to figure it out. Now, I turn off the the lights if I have to make delicate measurements, noise floor, etc.

[star882]

Originally Posted by Richard Ellis

The Eco-friendly argument is false as flourescents require more "environmental damage" to produce & dispose

In cold weather, that holds true since the heat is useful. In hot weather, the heat would be very unwanted. If your power is from coal, the mercury emissions from operating incandescent bulbs is more than the amount from operating CFLs and what is contained in the CFL itself.

But there's really no reason to use regular incandescents if you don't like CFLs. Halogens offer a better spectrum, are more efficient and last longer than regular incandescent, are dimmable, and are available with built in reflectors for more focused light.

I can't wait until LEDs become cheap enough for general lighting. (I know of an environmentalist (Allie Moore) who claims that she looks prettier under light from an array of "broadband white" LEDs...)

If you can't wait for LEDs, what about CCFL? Find a LCD TV with a bad screen (actual LCD panel is bad to the extent it's useless but backlight is still good), take out the CCFLs and power supply, then make it into a standalone light. You can expect great spectrum since the tubes are for lighting up a high quality video display, after all.