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 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 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!
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....
____________________________________________________________-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.
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.
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.
This is a serious issue for low level measurements. I have six ceiling "cans" with 65W incandescents on a dimmer. At the high setting they're pretty quiet, but at anything less they emit RF. I keep them full on most of the time. At my workbench is an adjustable floor standing light. It normally has a CFL in place, and the electrical noise level isn't too bad. For sensitive measurements I always keep a regular incandescent bult or a small halogen reflector flood around, and just swap it in.
I'd love to increase my efficiency by changing the ceiling lights for dimmable fluorescents, but the cost of the dimmable ones is way too high. I also have a high wattage florescent in the shop, but I've often finished what I set out to do before the silly thing warms up enough to put out useful light.
LEDs would be great, but the cost is still insane.
CH
I'd love to increase my efficiency by changing the ceiling lights for dimmable fluorescents, but the cost of the dimmable ones is way too high. I also have a high wattage florescent in the shop, but I've often finished what I set out to do before the silly thing warms up enough to put out useful light.
LEDs would be great, but the cost is still insane.
CH
Looks like incandescent is the way to go for critical measurements. With good grounding of the scope probes (all channels!) I can get rid of most of it.
Can't have everything I guess. These new flourescent fixtures are cheap and efficient, have great light levels (I can live with the color) and they even function in an unheated barn in the middle of winter.
Can't have everything I guess. These new flourescent fixtures are cheap and efficient, have great light levels (I can live with the color) and they even function in an unheated barn in the middle of winter.
Inspired, I did up this:
48 high intensity blue LEDs (bought 100 of these ~5 years ago on Ebay). Line voltage in, bridge, 200V cap from an old computer power supply and a 2 watt dropping resistor (680 ohm, LEDs drop 3.2V and are running at ~24mA). Simplicity itself.
Casts a pretty intense light, impossible to look at directly. High fashion blue too.
Fun with cheap LEDs!
48 high intensity blue LEDs (bought 100 of these ~5 years ago on Ebay). Line voltage in, bridge, 200V cap from an old computer power supply and a 2 watt dropping resistor (680 ohm, LEDs drop 3.2V and are running at ~24mA). Simplicity itself.
Casts a pretty intense light, impossible to look at directly. High fashion blue too.
Fun with cheap LEDs!
I know it is hard to believe, but somebody actually got a patent on that power supply. I have a shop light made that way using white LEDs. I added a constant current source so any number of LEDs could be used, up to max voltage.
Banned
Joined 2002
Banned
Joined 2002
I guess one, could buy some 5watt led's from The Full Line of Luxeon Star LEDS from Quickar Electronics and build a nice long led array for a bench light right 
Hi Steve,
CCS is a good idea. I just calculated the resistor based on the ~16V drop at 24mA. Rectifying mains voltage gives ~170VDC, enough voltage for the 48 I used. Just playing around but I think it would make a heck of a desk light with white LEDs and a diffuser - low power, no heat.
Elektor has a project that uses blue LEDs for mood enhancement (seasonal affected disorder nonsense, you know) with a much more complex power supply. I'll make a wall mount fixture to put this in and cast a blue glow over my workbench.
Banned
Joined 2002
Hi Steve,
CCS is a good idea. I just calculated the resistor based on the ~16V drop at 24mA. Rectifying mains voltage gives ~170VDC, enough voltage for the 48 I used. Just playing around but I think it would make a heck of a desk light with white LEDs and a diffuser - low power, no heat.
Elektor has a project that uses blue LEDs for mood enhancement (seasonal affected disorder nonsense, you know) with a much more complex power supply. I'll make a wall mount fixture to put this in and cast a blue glow over my workbench.
why not white ? doesn't the blue bother you or change the colour of things like colour codes on resistors etc etc ?
Jase
Hi John,
The company I was working for at the time was looking to get into LED sign lighting and I was the entire research department. They decided against pursuing this, but not before I got to make lots of signs in assorted colors as well as my bench light, several incandescent bulb replacements for home use and a couple of night lights for the kids.
Anyway, after the project was canceled and a new CEO came in, he decided the place was too messy. He walked into my cubical, pointed at a file cabinet an told me to "get rid of that mess". When ask what I should do with it, he replied"I don't care, I just want it gone". So now I have 1000s of hi intensity LEDs in every color made.
I know, that is off topic.
The company I was working for at the time was looking to get into LED sign lighting and I was the entire research department. They decided against pursuing this, but not before I got to make lots of signs in assorted colors as well as my bench light, several incandescent bulb replacements for home use and a couple of night lights for the kids.
Anyway, after the project was canceled and a new CEO came in, he decided the place was too messy. He walked into my cubical, pointed at a file cabinet an told me to "get rid of that mess". When ask what I should do with it, he replied"I don't care, I just want it gone". So now I have 1000s of hi intensity LEDs in every color made.
I know, that is off topic.
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