This is an electric puzzle that was shown to one of our electricians at a supply house. I have been told that hundreds of people have tried to solve it to no avail. I have not seen this thing but our guy has explained it to me. If there are any questions I will try to get answers. I have not tried to solve it myself as of yet but I will later.


Here it is,

There are two single conductors connected to a 120V male 2-wire cord cap.

Each wire, the hot and grounded conductor, goes to a different box made of porcelain or something similar and non conductive.

There is a single conductor between the two boxes.

In each box there is a toggle switch and a porcelain light socket with an incandescant lamp.

The toggle switch controls the lamp in the opposite box regardless of the position of the switch in the box with the controlled lamp.

The switch is a mini toggle switch. Don't know if it is SPST, SPDT or DPDT.

Our guy swears it works as described.

Good luck? Let me know what you come up with.

Brian

Edited female cord cap to male cord cap.

[This message has been edited by master66 (edited 07-04-2006).]

Do the bulbs light to normal brilliance?

I suspect they are running on half-wave rectified power, and there are some diodes involved somehow.

Not sure but I will find out.

Edit: no, thought I had it, but I didn't.

[This message has been edited by SteveFehr (edited 07-03-2006).]

NJwirenut's got it right.

The switches are SPST. There are two diodes in each box. The lamps glow at half-brightness due to half-wave rectification.

Here's the real question:

How do you get power to a setup like this that has a female cord cap?

Easy. I just need two el-cheapo extension cords, some of 'em wire stripper things, and some duct tape.

Ian A.

[This message has been edited by Theelectrikid (edited 07-03-2006).]

I added a couple caps and sent dxfs to Scott & Master66. Did you want dimmers with those? I was stuck at work on Emergency Standby until the fireworks were finished. I knew the answer immediately, just not my ECN password for the work computer.
Joe

Hello everyone!

The Schematic has been uploaded and posted to the Technical Reference section.

It can be found under the topic:

Lamp Puzzle!!!

Clicking the Hyperlink above will open that page.

Scott35

Similar circuits for signaling have appeared in electronics journals for years.

Another variant is to have a multi-way switch in one box signal four different states to lights in the remote box by feeding rectified positive, rectified negative, or straight A.C. down the line. The receiving end then shows lamp A, lamp B, both lamps, or none.

According to the information that I am getting, JoeTestingEngr was correct.

This "puzzle" was presented to one of our guys by Sam Scott of Scott Electric Supply near greensburg PA. Found out today that one of our other guys suggested to Mr. Scott a while ago and was correct also.

Thanks for the input.

Brian

Silly me, I didn't see the discussion link until after I sent a PM. Oops!

Anyway, here's how I think it works:

The diode connected to the switch is the key. When the circuit to this diode is completed, the current flows across the diode and effectively bypasses the lamp, diode and capacitor due to the other diode being connected backwards in respect to the diode on the switch. Without the diode connected to the lamp, the light would glow dimly. With the diode blocking the other half of the AC waveform, the lamp will only see the 0.7V or so dropped across the diode, not nearly enough to light a 120V bulb.

The polarized cap is probably to prevent flicker. I don't think it would be wise to screw in a CFL into this contraption!

The caps were optional. The diodes were mandatory.
Joe

That's easy. It's magic...

Seriously though, in my head I can make it work if the switches are DPDT and configuired in sort of a "three-way" set up, but each switch would affect the other switch. Let me put it to paper...

https://www.electrical-contractor.n...showflat/Number/148758/page/1#Post148758

This is the link to the drawing.
Joe

That was my next guess. The question throws you off if you're thinking in AC terms.

The Capacitors seem needless though. Lamps don't usually require much supply smoothing, unless I'm missing their intended purpose in the circuit?

Oops, I didn't read back. The capacitors are in fact optional.

Not only are they optional, but I think they are there solely to throw you off.

I took another look and each lamp receives the full AC wave, so those polarized caps would go BOOM anyway.

It might be CFL safe after all.

You probably ought to take a third look at it HWG. I didn't put the caps in there to blow up or throw off, but to smooth out. If you still can't make sense of it, say pretty please with silicon on top, and I'll draw it up a little more clearly.
Joe

Yup.... sure enough, the cap would work just fine. Man, this is a devious little puzzle.

Now I want to make one of these, put it in a nice Lexan box and confuse others. I have the pars laying around in the junk pile. I'll probably use neon bulbs instead of incandescents just too keep the contraption small.

I'm going to laugh if my professor puts this as a bonus question on a test in my Circuit Analysis & Design class.

I have seen some lamp designs that have a full wave rectifier and cap to reduce flicker but I honestly haven't had a noticeable flicker issue with incandescent lamps. The filament never has time to cool durning the tiny amount of time the voltage drops to zero in the sine wave.

How is it possible that a little circuit like this is so hard to understand? It's probably because I have never seen anything so weird! Is this a purely theoretical circuit or was a commercial design based on it?

The neons may give it away - only one electrode will glow, so people will know that there are diodes involved.

I don't know about that one.... the EE student's I know in the old dorm I was in may be completely oblivious! They have VERY little practical experience. They are mostly in it for the money, not a love of electronics. I played with neon bulbs all the time when I was a kid. I still want to know how they made blue ones! Mercury with a phosphor maybe?


The CSEs will have fits over this as well.

Most colored neons (blue, green, white) use a phosphor; the regular orange ones have a mixture of helium and neon, and the purple ones are argon. I too remember making relaxation-oscillator flashers and similar "idiot boxes" as a kid. I couldn't afford the 90V B-batteries so I directly doubled the AC line with no isolation transformer. How did we survive those days?

If you want to gets maximum yucks out of it, figure it out using two light dimmers instead of just switches. I think conventional dimmers should work, if applied properly. If not, try substituting sensitive gate SCRs and a pedestal and ramp circuit, for the diodes in series with the switches.
Joe

Here's a very quick outline of the 4-state signaling circuit that I described above: