220 volt worklight?

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No, it will result in a 50% duty cycle full-voltage waveform. It's a decent start, but given how non-linear an incandescent filament is, I'm not sure you'll get what you want.
On the other hand, most of the non-linearities are due to the resistivity of tungsten varying with temperature. The power cycling in a 50% duty cycle 60 Hz wave is probably fast enough that the temperature stays pretty steady.
Still, I suspect Greg's right; as a practical matter, it's probably the simpliest and cheapest solution to the problem.
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There is no need to speculate.
It works. I'd had a problem with a yard light dying whenever it was hit (lawn mower wheel, paper delivery bag ... didn't matter). I installed the diode, got about 1/2 the light (I knew this) but the bulb was still going strong 18 months later when I sold the house.
Another example was the short lifespan on an emergency exit lamp. Think it was high ambient temperature coupled with building vibration, but installed a diode there ... same bulb was going strong two years later when I transfered.
Remember those "energy saver" buttons sold in the 1980s? They were nothing more than a cardboard disk with a chip diode installed in the middle. Same result (though you'll be hard pressed to find them these days). Easy to install ... usually ended up soldering themselves to the lamp base and getting tossed out when the lamp eventually died. Use 'em if you got 'em.
Remember that you're going to need to increase the wattage of the bulb a bit more than 2x to get the same amount of visible light because at the lower temperature, the lamp is putting quite a bit of energy into the infrared region. Gives everything a reddish yellow cast instead of the tungsten-white we're used to.
Again, no need to speculate ... it works.
Radio Shack part number 276-1104 is a 1N4005 diode rated at 1 amp continuous, 600 peak inverse volts (PV or PIV). This should be good up to 200 watts (www.radioshack.com). Your local electronics parts supplier (assuming you don't have a RS near you) can offer you their part number for a 1N4005 ... you'll just have to ask.
Oh, and they are cheap ... think the RS price was $0.89 ... about the cost of one 100 watt light bulb. If you want it cheaper, you can get them for $0.017 each (in 5000 qty) from Digikey (www.digikey.com).
Rick
Who seriously thinks this thread has been thrashed about enough and deserves to die a quiet, dignified death. RIP
"Roy Smith" wrote ... snip ...

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Rick said:

Thanks for the support. <g> But...
Not to be pedantic, but actually the 'energy saver disks' were a negative temperature coefficient thermistor. High resistance when cold, but when current started to flow, they heated up, causing a drop in resistance, giving the bulb near full brightness. Eliminated the high current surge through a cold filament - which has a very low resistance.

Not necessary when using on 240v, however. The 120v bulb will glow at full brightness. At 120v, of course, this WOULD apply.
There is a difference between 120 to neutral and 240 across two opposite (or 120 degree/3p) hots. Or something like that... <g>
Greg G.
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How does that save energy? The bulb reaches thermal equilibrium in a small fraction of a second. Much too fast for the high inrush current to be a significant factor in overall energy use. I could certainly see how it might increase bulb life, by reducing thermal shock to the filament, but save energy? I don't see how.
If you want to save energy, use a smaller bulb. Anything along the lines of dimmers/diodes/thermistors just makes the bulb operate at a voltage/current/temperature point different from it's design point, and thus less efficient. Sure, you can make a 100W bulb draw 75W, but it'll put out less light than a 75W bulb running at full power.
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Roy Smith said:

Hell, I didn't design them, sell them, or recommend them.
They were marketed to extend the bulbs life, and the small residual resistance made them draw slightly less current. And yea, it made the light yellow.

I agree, but morons will buy anything if your dress it up in a colorful blister pack and promise the stars.
Greg G.
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Greg G. wrote:

Hmmmm. That explains some of the tools I've bought at HD. :-)
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Roy Smith said:

Yea, I'm pretty wary of much that is sold by Sears and Home Despot. Especially if it's brightly colored and makes unrealistic promises. Kind of like women... <g>
Greg G.
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Roy Smith said:

Yea, you're right - but I didn't want to get into all that. <g> Perhaps I would have been more accurate to say the bulb *appears* to be operating at half voltage.

The filament doesn't cool enough to notice the flicker. If it were fluorescent (and don't try it, it won't work), however, the flicker would drive you insane...

Works for me. Use a diode of 1 amp minimum for an 80 watt bulb, 2 amps for 160 watts. (Spec de-rated for safety...)
Greg G.
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Bob Davis wrote:

There are a lot of step up/step down 110V/220V converters available for $10 or less. Safe and easy fix. http://www.theelectroniccompany.com/SearchResult.aspx ? CategoryID0
Dick
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You could put a second bulb and run them in series, using standard 120v bulbs...
    Bob Kaplow    NAR # 18L    TRA # "Impeach the TRA BoD"         >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle:    http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org
Save Model Rocketry from the HSA! http://www.space-rockets.com/congress.html
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An alternative is to install a rectifier (diode) in series with one of the power leads. This will reduce the effective power to the bulb by 1/2. You will need a diode with minimum current rating of 2 amps or so to be "safe" rated at 400 volts or better. An alternative is to install a dimmer (most are rated at 600 volts) and only turn it up half way 8^)
-Bruce
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[...]

I get them for about about 80 cents in every store...
--
Dr. Juergen Hannappel http://lisa2.physik.uni-bonn.de/~hannappe
mailto: snipped-for-privacy@physik.uni-bonn.de Phone: +49 228 73 2447 FAX ... 7869
  Click to see the full signature.
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Not in the USA and your bulbs won't fit my wonky screw-in sockets.
Bob
Phone: +49 228 73 2447 FAX ... 7869

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Well thanks to the cool heads in this conference and the stearn chastisement about dangerous wiring, I fixed this for good. I ran a separate cord for the worklight and spliced it in.... piece of cake, legal, safe. The only part that urks me is that my new lamp cord is brown and does not match my black power cord. <grin> Maybe there's an aftermarket for worklight upgrade services. :-)
Bob

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Bob Davis wrote:

Is anal retentive spelled with or without a hyphen? :)
Congrats on the fix.
Rico
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You've gotten so many good answers, but what I haven't seen is the question of "why". How big of a drill press do you have that 220 is needed or even beneficial? I always thought that until the motor gets pretty big (2 hp or larger?) that 220 doesn't provide any benefits over 110. Sticking on external work lights, rigging the wiring on a major tool, and/or installing various combinations of lights and other electric gizmos to get around a problem caused by the switch-over wouldn't be my choice unless I received some significant benefit from running my DP on 220. Have you considered switching it back?
Dave Hall
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Hi Dave,
I'm pleased to ponder that question and give a reasoned answer. Actually I did ponder it before switching. Its not about the benefit for the drill press. Its about the flexibility of my 110 v power supply in the shop. I spent years working with barebones in the garage with one 20 amp circuit. Actually it was a 15 amp circuit (14 gauge) which the original builder mistakenly fed with a 20 amp breaker. My standard mode of operation was to switch off the air compressor when I wanted to run the bench grinder or shop vacuum. There was no such thing as running things simultaneously.
So finally, I did the work and ran power with separate breaker panel for the shop. I have the shop physically partitioned into three 110 volt 20 amp circuits. During the winter I occasionally use an electric space heater (13 amps). The drill press is 9 amps at 110volt when loaded. So that means I could not run the drill press and the space heater at the same time on the same circuit. Yeah, I know I could pay attention to which circuit things are plugged in, but that's a royal pain in the butt. After all that work wiring this place properly, I want to be able to run anything at any time within reason. My strategy from the get-go was to have three 220 circuits and sprinkle 220 sockets around liberally for the stationary shop tools.
Yep, it was a hassle to fix the work light, but its a one shot hassle and I get to retain my totally flexible power situation. I knew I would change my mind about the shop layout as I learned more and acquired more tools. I also knew that I would need to have a mobile shop, since I'm not blessed with a 100x80 foot area. The one thing I could do that did not cost much but greatly enhanced my flexibility was to put in ample power and have outlets everywhere. I have a 220 volt outlet every three feet in my shop.
Bob

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Dispite all the good answer, I read thru this entire thread waiting to see if someone would post the MOST logical answer (in my mind) to this problem and did not see it.
Think about the motor: in order for it to be usable at either 110 or 220 volts, it must havew 2 sets of windings. The windings connected in parallel for low voltage operation, or in series for high voltage operation. You currently have the latter configuration. If you connect the lamp across one set of windings (ie from line to "center-tap"), the lamp will "see" 110v. In effect you're using the motor as a transformer (it is after all just windings on a magnetic core).
Since you've already implemented a fix, you may choose not to do this, on the other hand you can get rid of that brown wire.
I had a Sears radial-arm saw, that's exactly how it was wired.
Good luck,
Abe
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Abe,
Your description is fascinating. At first, I did not understand how this would work. Then I realized that what you propose is an approximation, not a true tranformation splitting the voltage. Putting the light bulb across one of the windings means that you have two equal reactive loads in series, one of them wired in parallel with a resistive load (the bulb). The light bulb load is small compared to the motor windings. The net result is that the voltage drop across the winding-bulb will approximate half of the 220 volt. My guess is that it will actually be less than half because you've reduced the overall impedence in that half of the circuit.
The net result - the bulb will see something that it can run on, but the motor will see an imbalance in voltage across the two windings. It may be academic, but I'd rather not intentionally introduce an imbalance across the motor.
Bob

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Hi Bob:
True enough there will be an imbalance between the current in the motor windings. With a 60 watt bulb that will be about 1/2 amp greater in one winding. That represents about a 5 - 10% deviation, or about the same deviation that would result just from the maufacturing variables in building the motor.
While I understand your reluctance, as I said I owned a Sears radial arm saw for many years. It was wired at the factory so that when the user (me) decided to change from 120 to 240 volt operation I did not have to concern myself with rewiring the bulb. I owned that machine for about 15 years, ran it at 120 for the first 7 or 8 years. My son now continues to use it.
Good luck with whatever you decide. I just wanted to expose one more solution.
Abe
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