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What was your first circuit? Do you still remember it?
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Shay:

--- Quote from: Kleinstein on July 28, 2017, 12:17:13 pm ---The first circuit I remember was in school, more or less try an error putting together 4.5 V batteries, lamps and switches. We somehow ended up in funny version that used 2 batteries, 2 lamps and a single, single simple switch in a way that either one or the other lamp was active.  It took me very long to find out how this could work and for this reason I still remember.

Probably this is still a nice puzzle for the beginners.

--- End quote ---
In simple switch, you mean a classic SPST switch?
2 Voltage sources, 2 lamps, a single spst switch, that either state turns only one lamp. that's the puzzle?
brucehoult:

--- Quote from: Shay on November 25, 2022, 05:46:59 pm ---
--- Quote from: Kleinstein on July 28, 2017, 12:17:13 pm ---The first circuit I remember was in school, more or less try an error putting together 4.5 V batteries, lamps and switches. We somehow ended up in funny version that used 2 batteries, 2 lamps and a single, single simple switch in a way that either one or the other lamp was active.  It took me very long to find out how this could work and for this reason I still remember.

Probably this is still a nice puzzle for the beginners.

--- End quote ---
In simple switch, you mean a classic SPST switch?
2 Voltage sources, 2 lamps, a single spst switch, that either state turns only one lamp. that's the puzzle?

--- End quote ---

When I was about 10 our house was extended and a new hallway got a light switch at each end such that, of course, flipping the switch at either end would flip the state of the lights. That was fascinating!

You can do it using two SPDT switches and two conductors between the switches (and a 3rd that goes to the actual lamps), but I noticed the switches being installed were actually DPDT.

I sat down with pencil and paper and figured out that with DPTP switches you can actually generalise this to an arbitrary N switches! I wired this up with 4 or 5 as yet not installed switches and a 6V lantern battery and torch bulb and demonstrated to the electrician that flipping any of the switches flipped the bulb state. He was stunned :-)

I don't know if I've ever seen N>2 in the wild, so this result may not be well known.
Shay:

--- Quote from: brucehoult on November 25, 2022, 11:40:53 pm ---
--- Quote from: Shay on November 25, 2022, 05:46:59 pm ---
--- Quote from: Kleinstein on July 28, 2017, 12:17:13 pm ---The first circuit I remember was in school, more or less try an error putting together 4.5 V batteries, lamps and switches. We somehow ended up in funny version that used 2 batteries, 2 lamps and a single, single simple switch in a way that either one or the other lamp was active.  It took me very long to find out how this could work and for this reason I still remember.

Probably this is still a nice puzzle for the beginners.

--- End quote ---
In simple switch, you mean a classic SPST switch?
2 Voltage sources, 2 lamps, a single spst switch, that either state turns only one lamp. that's the puzzle?

--- End quote ---

When I was about 10 our house was extended and a new hallway got a light switch at each end such that, of course, flipping the switch at either end would flip the state of the lights. That was fascinating!

You can do it using two SPDT switches and two conductors between the switches (and a 3rd that goes to the actual lamps), but I noticed the switches being installed were actually DPDT.

I sat down with pencil and paper and figured out that with DPTP switches you can actually generalise this to an arbitrary N switches! I wired this up with 4 or 5 as yet not installed switches and a 6V lantern battery and torch bulb and demonstrated to the electrician that flipping any of the switches flipped the bulb state. He was stunned :-)

I don't know if I've ever seen N>2 in the wild, so this result may not be well known.

--- End quote ---

Nice. This is my crude solution to @Kleinstein puzzle:

L1 is parallel to B1, so by default it's on.
clicking on SW1 causes it to short L1 and B1 (would not recommend, but thats the best I came up with for theory) and puts L2 in series with B2.
Circlotron:

--- Quote from: brucehoult on November 25, 2022, 11:40:53 pm ---I sat down with pencil and paper and figured out that with DPTP switches you can actually generalise this to an arbitrary N switches! I wired this up with 4 or 5 as yet not installed switches and a 6V lantern battery and torch bulb and demonstrated to the electrician that flipping any of the switches flipped the bulb state. He was stunned :-)

--- End quote ---
Schematic please!
brucehoult:

--- Quote from: Circlotron on November 26, 2022, 11:01:19 am ---
--- Quote from: brucehoult on November 25, 2022, 11:40:53 pm ---I sat down with pencil and paper and figured out that with DPTP switches you can actually generalise this to an arbitrary N switches! I wired this up with 4 or 5 as yet not installed switches and a 6V lantern battery and torch bulb and demonstrated to the electrician that flipping any of the switches flipped the bulb state. He was stunned :-)

--- End quote ---
Schematic please!

--- End quote ---

Serious?

First and last switches only need one wire out, to the energy source and the lamp(s). Between every pair of switches one wire is hot and one wire isn't. Each switch either passes that straight though or else reverses which wire is hot.

It actually looks simpler on a physical switch because you're just connecting the 4 corner terminals out of the 6 in an X.
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