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Is it possible to use an LED bulb in a 3-way light fixture? Will all three work?

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Just FYI, an answer below indicates to me that the term "3-way light" is not entirely obvious to readers outside North America. – staticsan May 17 '11 at 2:19

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Unless you have a 3-way LED bulb (and a quick search indicates that they don't exist yet), it will light, but at the brightest light level.

A three-way incandescent light has two filaments: dim and medium. Each filament has a separate contact on the bulb's base. The brightest light level is provided by energizing both simultaneously. When energized, each filament is driven at the mains voltage, so applying that voltage to a standard LED bulb will cause it to produce its rated light output.

You'll probably find that (because the bulb's base is missing a contact), you'll have an "on, off, on, off" pattern as you rotate the switch, instead of "dim, medium, bright, off" like with a 3-way bulb.

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Thanks for the help! – user2676 May 17 '11 at 0:17
5  
the pattern is actually on, on, off, off. if it was on, off, on, off, you would never know because that's the same as on, off. :) – longneck May 17 '11 at 17:03
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3 Way LED bulbs finally do exist now: http://store.earthled.com/products/switch-switch3-way-led-light-bulb

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HEHE I made my own 3 way LED. I had a popped CFL and carefully removed the curleycues to get the base. I then put in two LED drivers (from 120VAC) and two LEDs which were 5 watt and 2 watt. I think luxeon stars. It works, albeit not as good as I would like. The LED drivers are tiny and did fit into the CFL power supply base.

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This doesn't seem to answer the question – Steven Jan 6 at 3:49
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-1 since the question was about using an existing LED bulb rather than building one. Also, CFL's contain mercury, so it's not advisable for others for break them intentionally and you didn't provide the procedure to connect the LEDs. – BMitch♦ Jan 6 at 12:32
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are you talking about a 3-way switch in a desk lamp? if so, that will be fine. those work by adding a second set of contacts in the base of the socket that if the bulb is a 3-way bulb then it touches those extra contacts. those contacts provide exactly the same voltage as the other contacts.

in short, this will not be a problem.

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up vote -3 down vote

This Q&A from GE, regarding CFL bulbs, should apply for LEDs as well: http://www.gelighting.com/na/home_lighting/ask_us/faq_compact.htm#three_way

Basically, unless the bulb was designed to work in a dimmed context, and says so on the package, you should NOT use it with a dimmer or in a three-way fixture.

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Here's a hybrid CFL/LED 3-way bulb: superiorlighting.com/product_p/19030led-tcp.htm – MT_Head May 16 '11 at 18:47
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well LED's are entirely different construction from CFL's, so it is unlikely that the Q&A will apply to both. Thanks though. – user2676 May 16 '11 at 19:15
Here's a PDF from the Department of Energy you might find useful/interesting: apps1.eere.energy.gov/buildings/publications/pdfs/ssl/… "LEDs face a dimming challenge similar to that of CFLs: their electronics are often incompatible with dimmers designed for incandescents. An LED driver connected directly to a line-voltage incandescent dimmer may not receive enough power to operate at lower dimming levels or it may be damaged by current spikes." – MT_Head May 16 '11 at 19:23
CFL and LED are completely different. CFL's require ballast starting (internal) at a constant voltage. LED's operate on low voltage (internal step down). Remember what Ass u me means? Sorry, down vote. Be careful, what you give as advice or an answer should be based on fact or personal experience. – shirlock homes May 16 '11 at 21:42
Although CFL and LED are completely different technologies, they both require constant voltage, which is why they can't be used with standard analog (incandescent) dimmers. To dim an LED, you turn it off and on many times per second (pulse-width modulation, or PWM), and your eye essentially averages the dark/light periods into an approximation of dimness. To work with an incandescent dimmer, your LED bulb needs a microcontroller that converts a lower incoming voltage into a lower PWM rate - which most don't have! Apologies for the link, but I stand by the advice. – MT_Head May 16 '11 at 22:10
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