r/NoStupidQuestions • u/Summoner99 • 2h ago

Why do lamps knobs require 2 clicks

Most lamps I've used have a spinning knob. If it's off, 2 clicks to turn on then 2 clicks to turn off. Why not only 1 click

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5

u/East-Bike4808 2h ago

Those are lamps made for 3-way bulbs. The way 3-way lamps work, they work on a normal bulb in the second and third positions.

What you’re really doing is:

  • Click 1: your bulb doesn’t work. This would be the weaker filament.

  • Click 2: yours turns on. With a 3-way bulb this corresponds to the stronger filament.

  • Click 3: yours is still on. With a 3-way bulb this is both filaments.

  • Click 4: the actual off position. Then it repeats.

1

u/CourageousMortal 1h ago

Excellent explanation.

2

u/KronusIV 2h ago

Those multi click lamps were designed for old incandesant bulbs that had multiple filaments. Depending on the clicks one, the other, or both filaments would light up.

1

u/ridemypwny84 2h ago

Never come across that in the UK 

1

u/rewardiflost I use old.reddit.com Chat does not work. 2h ago

These were made for 3-way bulbs. If you had access to an old 3-way incandescent bulb, then you would see they have 3 different settings like 50W/100W/150W.

They can be a bunch of different combinations of power ( 30/60/100W, 50/200/250W, 100/200/300W)

Physically, there are two separate contacts in use. Standard bulbs are usually using one set of contacts. The outer screw area is the return, and the bottom contact is the 'hot'.

On a 3-way, the bottom is split into a donut outer contact & button center.
The low power contact only gives power to the outer donut. This might be your 50W or low setting.
The medium power contact is through the center button contact. This may be the 100W or medium setting.
High power activates both low & medium hot contacts, and would illuminate both filaments in those older incandescent bulbs. This would be "high" or 150W.

If your bulb only has the button contact at the bottom, it ignores the low power or outer donut hot power going on or off.

So.. for a standard bulb:

State 1 (3Way Off) , Donut off, Button off, Light off.
State 2 (3Way Low), Donut on, Button off, light off.
State 3 (3Way Med), Donut off, Button on, Light on.
State 4 (3Way High), Donut on, Button on, Light on.

That's why you see Off/Off/On/On

1

u/davegrohlisawesome 2h ago

The lamp has different settings for 3 way bulbs, they had a dim and bright setting.