Lamps and Switches: CR4 Challenge (12/01/09)

assumes that the lamp is the only source of heating/cooling

The owner took the hot and neutral wires off of two of the switches and rewired to just one switch and turned it on. He went to the basement and looked to see if he could see lights coming from under all three doors to determine if each room was lit and had good bulbs. He went back to office and relabled the one switch that is on to rooms A, B, C. He relabled the other two switches as 'Spares".

1. Creating one switch is the answer already given by cadmechanic. 2. If the doors were sealed, you may not be able to see light from under the doors. 3. Assumes the owner is male. =>

1. DON'T connect a neutral wire to a switch unless you like watching electrical explosions. In standard building wiring, the only connections to a switch besides ground for the mounting plate are hot, switched or traveler (for multi-way switches) wires. The neutral wires are connected directly to the other side of the load.
   
2. The owner would have had to make two trips to the basement for this scheme. The first one would be a walk to the breaker panel to disconnect the light circuit...

Try again!

assumes that the owner has access to all units

Given they were QH lamps (sensitive to finger grease), I'd hope he felt the fitting. Also, it would be slightly better to switch that lamp off as late as possible, rather than before switching the second lamp. But another GA anyway (as the timing of the post suggests that it's likely to be independent of #1).

I agree with your assessment, but being a storage cubical one could speculate that any lamp would be covered with a cage? to prevent damage when moving materials about, and as for the other point raised about access, the owner would be required to have a master key, because of his duty of care in case of fire? And yes you are correct, #1 post had not been posted when I answered the challenge, I took a little extra time because I looked up info on QH lamps before I finally posted.

Regards JD.

No more good answers, all that's left is a digression. The retail business was in Dubai, where should the owner go to borrow money to upgrade its lighting installation?

I do not see enough information provided in this question to permit any way to detect a difference between the rooms. Therefore the answer must assume some added information that solves the problem. Here's my collection of plausible added information answers.

1. Proper archiving of wiring information is my simplest answer. This archive could be a hand written ledger, schematic wiring diagram or stored in a computer file in the office. A common electrician's trick is to write the information on the inside of the switch cover plate.
2. Light inside the storage room can be seen from outside the locked room. Remote access to the office switches by either networked computer or a cell phone link to a co-worker permits turning on the light of each room for identification.
3. One switch gets configured with a toggling ON/OFF signal while one is left ON and one remains OFF.
4. Video surveillance in each of the three storage rooms permit identification from the office. The trip to the basement was to get a can of soda.
5. Each switch enables both sides of a split phase and both phases drive an equal number of lamps. Two switches are turned ON but on of the two ON circuits only one phase has a fuse.
6. The load side of the lamp circuit for each room get terminated by three different value resistors just downstream of the switch. By bringing down a resistance measuring multimeter and/or a time domain reflectometer to each room, the owner measures the resistance difference from each room after temporarily removing all other loads (halogen lamps) from the circuit. Now that the switches for each circuit are identified, the owner fabricates and replaces the missing labels on the front of the faceplate and writes on the inside of the faceplate the room numbers to prevent this problem from happening again.

IT'S ALREADY BEEN ANSWERED. Turn two switches on and leave on for two minutes. Leave switch one on, turn switch 2 off. Go to the rooms. The ones with lights on are switch 1. The ones with the hot bulbs that are off are switch 2. The ones that are off that have cold bulbs are 3.

Yes, it has been answered making the assumption that one can get inside the locked rooms and be capable of at least a qualitative measurement of the lamps temperature. What if these three locked rooms have extremely high heat exchange capability like a flash freezer? What if these three rooms are independently leased storage facilities and the building owner does not have keys to the locks? Why else would these rooms be stated as locked?

My point is not that the bulb temperature answer nor any of my other equally valid answers are more or less plausible or even practical. (Certainly trying to do a TDR measurement on lighting wiring would not be practical.) My point is that they must all include some assumption to answer the question. Why not assume that this information is available somewhere else, possibly written on the door to each room. So possibly these are all valid answers. Maybe none of these answers are correct for no assumption is needed, we just haven't found it yet. Then again, the challenge maybe just hastily posted and missing a critical part that we are assuming.

Or what if; he just sent someone down there, switched each on and off then went down and asked what happened. Or having heard about what happened by phone or CB, just went down to make a bossily appearance? And how did he know one or more globes weren't blown if he hadn't been down? Or what if; 'correct labeling' was A, B, C and the rooms/areas, previously un-named, are so now? Or what if his PA did the switching - then he could establish they worked and what order - in "once".

And what are we all going to do now?

He could also disconnect power to all three lights at the switches, shunt the wiring to the lamps with three different resistors, then remove the lamps and measure the resistance at the fixtures.

Hi

1) Switch on one switch for 5 minutes and switch OFF

2) Switch on second one - now make VISIT each cubicle check the cooler one, lit one and switch OFF but hot one.

This will solve the problem

Or maybe he switched on the 'first one', went down and discovered that 'the first light' was on - said to himself "the electrician has wired these logically".

Unlike the one who did my latest 'digs for the duration', which is so illogical and anti-instinctive, that I always get it wrong and think "where is my screwdriver?" but then think "probably not a smart idea at 1:00 am half pissed on corporate booze" - then it's daylight again and I just toddle off again, or get completely distracted by CR4. And speaking of CR4 and logic and recent threads; why is this 'owner' using halogen? - in a 'store room'? Why not fluorescent?

Some very interesting arguments, but consider this one. The challenge specified a quartz halogen lamp, why? my thoughts when answering the challenge were, should a further check be made on a second room if the lamp was cold? and if the next unlit room lamp was also cold, do we have a blown lamp problem? But as pointed out to me in the past, one should enter into the spirit of the challenge.

Regards JD.

JD, you raise an excellent point. Maybe he just got lucky with the one's he turned on?

Well I would have "entered the spirit of the challenge" had you not already solved it in principal and therefore my only recourse was to add a vote to you to even things up _{(and then fool about in search of the "tangent" for the rest of the week)}

_{Though Red's 'locked' point has me thinking the guy must have an optical IR pyrometer or B&W CCD or night vision goggles or maybe a bit of wax on a stick (which would 'improve' the life of QH, as would 'feeling' the globe)}

^{It would be extra fun if the "answer" is; "He used the Whizzbang 3600!" and you guys just shot down the 'impossible problem' that makes it 'a must have' bit of kit.}

Quartz halogen, produce a fair amount of heat. Turn 1st sw on, leave on for half an hour or less, depending on ambient. Before going down to the basement, cut the 2nd sw on and leave the 3rd sw off. Should be able to detect a temp contrast between the 2 cubicles, which show evidence of having their lights on. Label accordingly.

"cut" means to separate something. "Cut" a piece of cake for example. To "cut" something "on" is an oxymoron. I can see "cut" something off by positioning the switch to "off"

I like it. Simple, no assumption required other than being the owner he/she decided a separate circuit for each locked room has become more of a headache than an asset.

I "swiped" your answer without being aware. A thousand pardons, and a GA to you.

My 10th grader asked me the same riddle a month ago....

He turned one on for a little while, shut it off, then turned another one on and left it on. He then went down saw the one that was on and felt the two that were off to see which one was warm...voila!

was the room locked?

He placed one switch in the off position.

He turned one switch on and waited a short period and then turned the other switch on and visited the basement.

The light that was off is controlled by the switch in the off position.

The brightest lamp is controlled by the first switch turned on and the dim lamp is controlled by the second switch he turned on

Lee Seggern, CLR Design

You are thinking of mercury vapor lamps not quartz halogen which are instant on/off.

At last: a boss that knows how to do things! Now, there's a turn-up for the books!

# the switches 1-3 turn on switch # 1 for a minute and then turn it off turn on switch # 2 and head to the basement The lit bulb is operated by switch 2 The unlit & hot bulb is operated by switch 1 the unlit & cold bulb is operated by switch 3 If the 1st unlit bulb checked is cold, the second cannot be assumed hot due to the possibility of a blown bulb.

.....or a blown fuse.

So what if the janitor comes in to empty the trash 30 seconds after the owner leaves his office and flips some of the switches?

Noone ever said he couldn't unlock the cubicles and leave behind a remote camera when he went down to the basement.

The owner will first make ON any one switch and leave it for some time, say 1min, and will switch it OFF. Now, he will switch ON next switch and will go down to basement. He will go to all thre three rooms one by one and will make following observations:

1. The lamp, which is lighted, off course, is having switch which he left ON and came down to basement.

2. Rest two bulbs, he will touch by hand. The lamp which is hot is having switch, which he made ON first.

3. The cold bulb is having switch which was not touched by owner.

Very Simple :)

from: ratan

he turned one switch on for 5 minutes (this is switch two) and then turned it off. then he turned one of the other switches on (this is switch one). when he went to the area he found the one light on ( ident switch one) and one light off but fixture still warm ( identified switch two) and the last was the one light off ( ident switch three)

answers are assuming the owner knows the switches ON and OFF positions. What if the toggle switches ON and OFF positions are also unknown? Or if the switches have normally closed contacts or normally open contacts and unknown state?

hallogen bulbs have a cool down period also. So turn on switch A and let heat for about 30 min. turn off all switches. wait 1 min. turn on switch A & B. go to basement. Light B will be on. Light A will come on in a few minutes and Light C will stay off. You can see the light under the doors if you can't get into the locked cubicles.

You are describing mercury vapor lamps....not quartz halogen which are instant on/off

Love it, have vote.

assumes each unit is rented to someone

Not true, Fred assumed several things in solving this puzzle but as each assumption proved false he continued onto another plan that did not require that assumption. So if the the rooms weren't rented his plan to enter and measure lamp temperatures would have solved the problem as people keep repeating here. (Haven't you people heard of plagiarism. Don't repeat somebody else's answer.) So the rooms being rented confirms why the rooms were locked but more importantly were a discovered fact and not an assumption by Fred.

You assume that he has access to the rooms.

Leave one light switch in the off position and the other two in the on position. Disconnect the common wire from one of the "on position" switches. One light will be off and one of the other two will be dimmer.

Turn on the first switch and wait a few minutes, then turn it off and turn on the second switch and go to the basement. Check the light fixtures, the one connected to the first switch will be hot and off, the one connected to the second switch will be on, and the one connected to the third switch will be cold and off.

AJH

The owner went to the basement while an employee flipped the switches in order from left to right (or top to bottom or whatever orientation), and the owner made a mental note of what order the lights light up in what order of the sequence.

The problem question never stated that the owner was alone at work.

Turn two switches on and wait 15 minutes. Turn one of those switches off. The switch that was not turned on will be A, the switch that was on and then turned off is B, the switch that remains on is C.

Go downstairs and feel the side or door of each container. The cold one should be labeled A, the warm one labeled B, and the hot one labeled C.

Turn on 1st switch for 10 min. Turn off, then turn on 2nd switch. Hobble on down to basement. Dark room with warm globe is switch 1, lit room is switch 2, other dark room is switch 3.

have a look at the cables

I bet that owner is not an engineer at all!

It usually takes three engineers to fix a light bulb!

Two should be enough ; 1 to hold the lightbulb, and 1 more to operate a crane and rotate the room.

Everyone has answered it with a thermal solution.

Here is an electrical solution.

Connect a decent resistor(may be another halogen lamp) across one of the switch's (e.g. switch C) terminals so it reduces the voltage to that corresponding lamp in the cubicle. No you have three states for the swithces.

Light A) ON

Light B) OFF

Light C) dimmed because of reduced voltage (leave the switch off)

Turn one light on. Go to basement, remove one lamp from an 'off' fixture. Return to switch bank. Label the 'on' fixture, use a continuity tester to find the open circuit with the lamp removed, label that one, now there's only one left.

What a great idea. Please also let us know how you get inside the locked rooms. Then i will give you a GA for your answer.

What, the owner doesn't have a key? I guess he called the locksmith. Otherwise, if there is no access whatsoever, who cares if the lights are off?

This is an old one. Turn one switch on for several minutes, then turn it off. Turn on a second switch and quickly go into the cubicles. One light will be on, the switch on controls that lamp. One of the other two lamps will be warm, the first switch controls that lamp. The third switch controls the lamp that's off and cold.

The owner took 3 reels of fibre optic cable down to the basement and fed one end of each under the 3 doors. He then went back to his office and turned each light on one at a time and viewed which light came on down the fibre optic cable.

The owner hired an electrician and a locksmith to fix the problem. When they completed the job, the owner made a trip to the basement to verify.

The owner would turn on one of the switches for a few minutes and then switch it off. He would then switch on one of the other switches and leave it on as he visits the basement cubicles. The fixture that is off but still warm or hot is the first switch he turned on. The one that is lit is the second switch he turned on and the fixture that is off but cold is the switch he did not operate.

Since the challenge states that there are "three locked storage cubicles" and does not explicitly state the owner has the keys, it could be assumed that direct physical access to the lights is not possible so the owner cannot feel the bulb's temperature. However since a basement is not normally a finished space (at least in a commercial building), there should be exposed conduits to the lighting fixtures that can be visually traced to each storage cubicle. There should also be pull boxes or conduit connectors that could be opened up to get a clamp-on ammeter on one leg.

First, in his office the owner pulls all three switches out of the box and verifies switch positions using the clamp-on. He turns all three switches off and installs two different power resistors (50Ω & 200Ω) in the dead leg of two of the switches. He then turns on all three switches and measures the three (presumably different) current values.

Next, in the basement the owner surveys the conduit runs to each cubicle and identifies the nearest box or connector that can be opened for each run. He then opens each conduit and again measures current values. These values should directly correlate to the values measured at the switches in the office, so the owner returns to his office and labels them accordingly.

He turned the middle switch on and verified that the light in the middle cubicle was on, and assumed that the other switches controled the lights on either side.

a special tool call multimeter may help

I am assuming the owner could see the the lamps and the lamps were all good to start:

1) Turn on one switch and then wait 10 years.

2) Turn on another switch.

3) In the basement the owner would see one lamp black, one lamp off but clear, and one lamp lit.

This was a previous owner of Harrods, and the office is at the far end of the building, so the method of 1 or 2 will not work. Watching the ammeter, he switched all three lamps on one after another. One of the bulbs was not drawing any current. So he turned that circuit off again and went downstairs with a spare bulb (may as well kill two birds with one stone), turned off one of the functioning lights using the local switch at the bottom, and returned and switched the remaining two lights off again.

Or, he asked his electrician to stay behind and turn the lights on in order.

Did any one say owner does not have the key ? (cubicles may be locked, but the locks can be unlocked ) And if owner does not have key, he can get it.

Of course if the owner is still in office so are few others, they can be sent with key and owner can swtich them one by one and then go and ask which is first and which one second.

And if this is cheating (the quizzer) - then able to see light too is, and so is multimeter et all... .

2. Assuming he can see the light , no staff present, no keys either, get some thing put in series (say a room heater) and then go watch the dimmer lamp and brighter lamp, the third of course is not to be switched on. (this method I posted earlier but seemed to be lost in traffic- the first one is of course part of the latest neuron activity )

3. Put a timer on the three switches (the decorative lamp type) with different timing and then go watch which one is 2 minutes on and which one is 5 minutes on

And going by the assumed Quiz condition (no visible light from cubicles, of course bulbs can not be touched, no instruments- multimeter etc, no keys,...)

All the bases seem to be covered, so I'll try one last time; Ballpoint pen ?

Just trying to help Kris

The answer by Jaxy (#1) still seems to be by far the best, as it makes the least assumptions, not requiring even visibility of the light from outside a (locked) cubicle. JD's #2 would need access to the cubicles for checking the bulbs. The answers which require additional instruments or tampering with the switches or wiring circuit are at best lacking in elegance.

The only assumptions made in #1 are that the lamps are all initially (known to be) off, and the switches have known on/off positions, and of course that all components are in working order. There is nothing extraneous to the 'spirit of the challenge'. Since quartz halogen lamps reportedly generate a lot of heat, the the owner only needs to feel the outside of the cubicle doors to see which one is warming up, cooling down or remaining cool. Even the time delay aspect has been covered in the answer. I wouldn't consider refrigerated chambers to be a reasonable assumption in this challenge.

I would suggest a small improvement to #1. The second switch is turned on when the first is switched off.

Let me make my second ever attempt at awarding a GA (tried once over a year back and it did not register!) =TeeSquare=

GA. If we assume nothing other than that we can feel the temperature of the cubicle from the outside, this can indeed be more robust than #1 - particularly against the cubicles being of different sizes or wall thickness and the lit cubicles also warming the unlit one*.
All being well, we can now eliminate as follows: cubicle heating fastest after arrival is the one that is last one switched on. The one of the other two that is warmer initially is the first to be switched on (if the first and the unlit are very different and adjacent, we might also need to look at cooling rates).
As "cubicle" properly implies a space large enough to sit in, I think I'd give it at least five minutes.

*Even here, the analysis could require impractical measurement precision if the cubicle insulation and dimensions are too different...

The way I solved a network wiring issue concerning a business center in a hotel was to send a helper into the network room where the 19" rack mount switch resided, and simply called him on his cell and we discussed which lights were active on the switch as I disconnected various computers.

Simple, but very effective. And we had several more than three 'lights' to figure out.

We did in fact have more than one person, used cell phone technology, and had access to each room which this challenge does state just one person was involved.

My favorite comment so far was the TDR.

CleanFacets

You turn on switch A and leave it on for a few minutes, then turn it off. Then you turn on switch B and leave it on while you investigate the offices. The bulb that is warm but off is switch A, the light that is on is switch B and the one that is cold and off is switch C

Quartz Halogen Lamps produce heat. The Owner Timed the Switches one Minute apart. He then went to the basement and felt from Hottest to Coolest.....Easy!

Turn on one light and leave it on long enough for the lamp housing to become hot.

Turn on a second lamp and turn the first one off.

Immediatly go down to the cellar. One light should be on (obvious). Of the other two one should still have a hot or warm lamp housing (the one you first turned on). The third light should be off and cold.

But these locked, sealed, fire-proof cubicles are rented out to customers for secure storage...

Quartz halogen lamps get hot when on. He labeled the switches 1, 2 & 3. Then with sw1 off, turned sw2 and sw3 on. He waited 15 minutes to make sure the lamp controlled by sw1 was cool, then switches sw2 off and immediately went to the basement. Only 1 lamp was on, that was sw3. Of the two lamps that were off, the warmest lamp was sw2, the coolest lamp was sw1. He noted which cubical was which and relabeled the switches in the office.

why even bother to go downstairs.

call electrican to do the job. its unionized..

m$ 0.02 worth

What really makes it funny is calling an electrician repeats answer #64

Don't knock it CM, now it's official; you are Quotable!, ()

My mistake!

The owner makes sure all switches (say switches A,B and C) are in open (no power) position. He can do this by opening the switch housing and looking at the switch contact points as each switch is operated. He waits a good few minutes then switches one switch on and notes which one it was (say switch A). After a few minutes he turns it off. Then he immediately turns another one on and notes which one that is (say Switch B).

Then its off fast to the basement. The light in the cubicle which is lit corresponds to Switch B. Then the owner then feels the lights in the other two cubicles. The one that is warm corresponds to Switch A (the switch which was just turned off) and the one that is cold correponds to Switch C (the switch that has been off for a long time). The owner can therefore note which cubicle correponds to which switch.

The owner returns to the switch house a labels the switches to match the correct cubicles (and each on/off switch positions if necessary) before screwing everything back into the wall-mount.

Since these are quartz halogen lamps,the glow remains for a while even after the switch is turned off.The owner must have lit a lamp first,then turned it off and switched another on.This way,one room will remain lighted,another partially lit and the third dark.