Light Switch

[laketime]

I have a friend who has a foot switch on a two lamp standing reading light. He tells me the switch is broken that you used to step on it once (1) lamp comes on, second step both lamps come on, third step all off. When I look at the fixture there is just a standard 2 wire lamp cord going up to the bulbs. How can it switch the lamps separately?

 

[poeboy]

is each side of the cord going to the center of the lamp holder base? or are they using one side for the screw shell (or what ever the base is) and the other for both centers???

I'm still trying to figure out why a 3 way lamp works in LOW, MEDIUM, and HIGH modes in a lamp..... but if you put a regular same wattage lamp in it it only lights up in the MEDIUM mode.....

 

[walkerj]

I think your friend is confused, or he tried to rewire the 'broken' switch with two-wire cord.

 

[laketime]

I think your friend is confused, or he tried to rewire the 'broken' switch with two-wire cord.

Yeah, I agree. Do not see how it would work with out (3) wires going up to the lamp bases, (2) switch legs and (1) neutral.

 

[Cold Fusion]

Yeah, I agree. Do not see how it would work with out (3) wires going up to the lamp bases, (2) switch legs and (1) neutral.

If it came with a two wire cord from the switch to the lamp, the lamp would have to have some electronics in the base - sort of an electronic stepping relay. I've never seen one, but the concept does not sound any tougher that the dimming touch controlled lamp I've got.

cf

 

[al hildenbrand]

When I look at the fixture there is just a standard 2 wire lamp cord going up to the bulbs. How can it switch the lamps separately?

It can't. Not without a third conductor, or a solid state module to "receive" the instruction from the foot switch.

I agree that the recollection of the lamp owner is suspect, that it is definitely not definitive.

 

[480sparky]

..............I'm still trying to figure out why a 3 way lamp works in LOW, MEDIUM, and HIGH modes in a lamp..... but if you put a regular same wattage lamp in it it only lights up in the MEDIUM mode.....

3-Way lamps have two filaments. Let's say it's a 50/100/150, so it will have a 50w and a 100w filament. The switch turns on either the 50, or the 100, or both (for 150).

The reason a standard lamp only works in "Medium" is there are three points of contact for a 3-way lamp, but only 2 for a standard. And the center of the socket is what would go to the higher wattage filament in a 3-way. The contact between it and the screw shell makes contact with nothing on a standard lamp.

 

[laketime]

3-Way lamps have two filaments. Let's say it's a 50/100/150, so it will have a 50w and a 100w filament. The switch turns on either the 50, or the 100, or both (for 150).

The reason a standard lamp only works in "Medium" is there are three points of contact for a 3-way lamp, but only 2 for a standard. And the center of the socket is what would go to the higher wattage filament in a 3-way. The contact between it and the screw shell makes contact with nothing on a standard lamp.

22 years as an electrician and I just learned how a 3way light bulb works. Maybe I need to study more.......:roll:

 

[al hildenbrand]

Maybe I need to study more.......:roll:

Never stop asking questions.

 

[480sparky]

22 years as an electrician and I just learned how a 3way light bulb works. Maybe I need to study more.......:roll:

You've never looked at a 3-way socket and/or a 3-way lamp base?

 

[dicklaxt]

I agree with Al H on this one,,,,,,,,,,,It can't. Not without a third conductor, or a solid state module to "receive" the instruction from the foot switch.

The electronic module would have to be on the fixture itself.I am from the old school of hard wired relays amd I believe with a hot and neutral at the fixture I could make this happen with relays and I know that the electronic Gurus could replicate on a card the size of a quarter.

I think I'll see if I can do it with relays,probably will need a timer or two to stop contact races,,,,,,,,,
dick

 

[jmellc]

I don't see how that could be. I agree that the guy probably tried to fix it himself with std 2 wire lamp cord. Check out the foot switch, it probably has 3 terminals, maybe 4. Should have 2 hots, neutral and maybe ground. Needs #18 SJ cord, either blk red wht or blk red wht green.

 

[jmellc]

Never stop asking questions.

A young punk once told me what I didn't know would fill an encyclopedia. I rebuked him that what I didn't know would fill libraries and warehouses.

 

[LarryFine]

22 years as an electrician and I just learned how a 3way light bulb works. Maybe I need to study more.......:roll:

It's exactly the same thing as a dual-filament automotive taillight/brakelight bulb: dim for taillight, bright for braking, both for, well, both.

 

[LarryFine]

You've never looked at a 3-way socket and/or a 3-way lamp base?

Or a three-bulb lamp with 1-bulb/2-bulb/3-bulb operation.

 

[LarryFine]

I agree with Al H on this one,,,,,,,,,,,It can't. Not without a third conductor, or a solid state module to "receive" the instruction from the foot switch.

Well, there is another way: A diode switched in or bypassed, and the lamps just paralleled.

I once made a hall-bathroom bright/dim for a kids' bathroom fixture with a diode across the switch.

 

[kwired]

I can see having 2 light levels easily with a 2 wire cord, a diode and a double throw type of switch.

3 light levels requires more solid state components (or resistive but they will make more heat) in the switching device.


added:
Larry is faster than I am

 

[LarryFine]

added:
Larry is faster than I am

"Tag, yer it, baggy-eyes!" :grin:





"Overachievers underestimate the rest of us."

 

[hurk27]

A long time ago I pulled couple switch's apart for a 3-way lamp, it was kind of clever in how they do it, one had a rotating disk with brass contacts, when it was rotated by the pull chain it would latch with one contact connecting with the conductor to the ring of the bulb, a second pull would rotate it to touch the the conductor to the center of the bulb, the one more pull will hit both, very similar to the way a keyless pull chain works,kind of like a ratchet, the other type was nothing but a cam type that would just bend metal contacts as it was rotated and the different contacts would make contact depending upon the cam position to the two contacts to the bulb.

 

[dbuckley]

You could switch two bulbs using a two core cable, but you would need to use diodes, and the bulb filaments would need to be rated at about 74V rather that 120V because each one would only ever get one half of the mains cycle.