ok here is the deal i have a extra credit project due fo res. wiring class. and i am LOST. i need to hook up 6 switches with 6 lights, there can be only two lights on at a time when u turn on one switch it turns on the light in front and turns off the one in back off but leaves the light right above it on, like lights in a long tunnel. i can use any combination of the following single pole/double pole/three-way/four-way.

i kinda know u have to have three-ways at each end but after that i am very lost. any help would be greatly appreciated, thanks in advance

I have bad news for you....what you describe cannot be done legally these days.

The reason for this is that you end up switching the neutral wire, which violates the National Electric Code.

I concede that this arrangement was once common- but those were the days before polarised plugs, ground wires, PLC controls, and the like. I will admit that it worked extremely well- almost as if the lights "knew" which way you were walking.

Nevertheless, I think this is one clever electrical trick you don't need to know.

Ok Reno, you have me intriqued!~(MS) Hows it done? E-mail me as to not give this studen free answers for the class he needs to figure out on his own......

If you must have switches, use LV switches and logic to control appropriate relays (perhaps solid state) or contactors to control lights.

I'd have to play, but I think it might be doable to some degree with 3 way switches.

If it were me, I'd use motion detector lamp holders, and forget using switches altogether.

hey e57 u was a student at one time and problably would had wanted help on the subject to. reno i see where u are coming from about sprading bad habits, and i dont need the extra credit i have a 97.5% but i just wanna show the teacher up he look down on all his students like we are all idiots about everything everything i have learned i have learned on my own because he is one of the kind of teachers that learned about it the went right to teaching. so he has never really had to but his hump to make a living i guess thats why he has a attitude with everyone

classicsat
it has to be regular switches like found in every home out there and 6 cheap style screw in lamp holders. off all the things to have for extra credit i see in no way that this would ever have any effect on residetial wiring. i think he has to much free time on his hands to think this b.s. up

Sorry, friend, I did not mean to be curt....but this is a very popular forum, and it would be wrong to get into this sort of switching.

I am sorry your instructor is a jerk, but I doubt you'll ever really change his attitude.

I think you could do it by using three ways so that the common is hot, one "traveller" srew goes to the bulb in front, the other srew goes to the bulb behind. then when you flip the switch it turns one off as it turns the next on. they would alternate having the one directly above on the sitch in front and behind. It could be done, it is a logic riddle. I'd need pencil and paper to really figure it out.

I know the answer to this and it is simple,
strokezilla, If you can't work this out, that's sad, to say the least, especially if you want to be better than your teacher.


[This message has been edited by Trumpy (edited 09-22-2005).]

strokezilla...

the trick is to know how a three way switch works and using it to your advantage.
yes it is illegal to switch neutrals but this is a THEORY question...one asked of about every apprentice.
bill

We seem to keep hinting at this, and then saying 'you shouldn't know about this because you shouldn't use it.'

My opinion is that every electrician should know about wrong ways of doing things, and why they are wrong, so that they can recognize and correct the problems. With this in mind, strokezilla, I'd suggest that you look up the 'french three way' circuit. The same circuit goes by lots of different slang names. It is a three way circuit that requires switching the neutral, and it is a big no-no, for a number of safety reasons.

Once you understand how a french three way works, then you will be able to 'generalize' it to your problem, and come up with an 'illegal' answer that would function as your instructor described; 6 switches, 6 lights, flip a switch and one ahead turns on and one behind turns off.

Personally I would rather set it up with seven switches and a way to turn all the lights off.

Finally, if you are allowed to use double pole double throw switches, then you could make this system work as described, and you could make it legal. I think that the illegal approach is more 'interesting' as theory, but not what you should install.

For extra extra credit, analyze exactly what is wrong with the 'french three way', and all the ways that it violates code, and find a 'work around' that uses the essential circuit concept but makes it code legal. (I don't even know if this is possible, but I have a few guesses.)

-Jon

I can do it with 6 swicthes, 6 lights, if you throw in a plc.


Dnk......

I may not have the specified problem quite right, but if what is desired is to have at the beginning of the tunnel/hall is a switch and a light overhead, then another switch say halfway to the next light, and so on down the tunnel, then:

first switch (SPST) switches the feed from the panel and powers up the entire system (presumidly the subsequent switches were left to power light bulb #1 by the last person who came back thru the tunnel) and light bulb #1 (fed on the hot side thru a SPDT (3 way)). The hot wire from the first switch feeds the center of this 2nd switch (#2), and one side of it feeds bulb #1. The other side of this switch feeds switch #3 (another SPDT 3 way) center leg, and one side feeds bulb #2 and the other side feeds a 4th switch, and so on. No neutrals are switched, all switches are on the hot side. Someone entering the hall turns on switch #1 and bulb #1 lights. Halfway to bulb #2 is switch #2, the person switches it and bulb 1 goes out and bulb 2 comes on, and so on. This assumes! that the previous person who went down this hall returned and switched all switches back to their original positions though. If I can't count on that, then things really get messy...

I didn't have enough fuel (beer) to realy think about it last night, but came up with the same meathod wa2ise mentioned with some modification. Which I won't go into for the sake of the student.... But am wholey confident that it can be done without switching neutrals, and operate in the intended manner from either direction. Or from the same direction twice. (I have to draw it out to be sure, which will take some time, and some beer.)

Now, last night while sipping my only beer, and pondering this puzzler, I realized that I have done this problem 15+ years ago, in school. It was an epiphany! Now, without giving it away, here is two clues:

Voltage drop can be an issue

Each switch changes state twice

Now I need some beer to absolutely sure.

(Jon, what is a "French 3-way? The same as a Hollywood 3-way?)

winnie i looked into the "french three-way circuit" and wow that looks like a mess waiting to happen and see why it is illegal, but would it still be illegal if u reidentified the neutral as a hot wire?

[This message has been edited by strokezilla (edited 09-22-2005).]

OK I did it! (with no beer in the house at all...)

It could take a day to draw it up well though...

We'll wait; we have time.

Yes, because (a) you are switching the grounded conductor and (b) in one of the "on" combinations you'll have the grounded side of the supply on the center contact and the hot on the screwshell.

By using a series of cross-connected French 3-ways you could achieve the desired result easily enough. I'll sketch out the circuit when I get a few minutes to spare.

Scott,
Are you using DPDT switches at each location, each light basically on a normal 3-way so that one half of each switch forms one 3-way for the light in front and the other half is the 3-way for the light to the rear?

I'll wait to see if that's your solution before sketching that one out, but as I see it
that would work and be perfectly "legal" too. (hot side switched, screwshells all direct to the grounded conductor).

It would sure use some wire though!




[This message has been edited by pauluk (edited 09-23-2005).]

strokezilla,

So when is you're project due?

next thursday, everyone in the class is doing stuff like this to try and get help in doing it, we were tempted to open the display up, but the teacher walked around the corner when we were planning it lol, so i dont think that would be a good idea now i sure he will be watching it like a hawk.

Thursday...

OK I and others feel that we cant just show you.... You're a student, and this is a learning process.... I and others have schematics we could just send you, but aren't... And we too have some different ways of doing it, there are several.

However, I am gonna give you a hand in the way you approach the problem. (This is how I approached the problem.)In this trade, troubleshooting, and by proxy, design of electrical circuits requires an understanding of the required operation... So lets detail what the circuit needs to do:

• Either needs, or is limited to 6 lights, and 6 switches.(For now, just draw on a piece of paper what is known. i.e. 6 circles in a row representing the lights.)
• Only two lights can be on at one time.(Assuming you're entering a tunnel, the first light is on. Mark it with a pencil.)
• The switch used, changes the state of the light behind you, and the light in front of you.(By this, one can assume that the maximum of two lights that can be on, are going to be grouped together, pencil the next light on.)
• The light over your head does not change state while operating the switch at that location.(The switch doesn't operate the light over you're head.)
• Limited to the use of toggle type switches. (3-way, 4-way, Double-pole, or single pole. So for visual referance draw an example of each type of switch at the bottom of the page.)

For simplicity, assume if it is a DC circuit, every light has a negitive. Or if AC every light has a neutral. Just focus on what the light needs to operate, a positive, or hot to operate. And removal of that positive, or hot to shut it off.

Now "Walk the circuit"

You enter the tunnel, and approch the first light, and switch. The light you are at, and the light in front of you are on.

At the next light, you need to turn the one off behind you, and the one in front of you on.

Look at the examples of available switches, and try each one in the situation. Be creative, because they don't have to be used in the traditional way.

Now, you are on your own....

Definitely a point to emphasize. You need to apply some lateral thinking with problems such as this and not be trapped by what you might regard as the "normal" way to use a certain type of switch.

I think that it can be done code legal with one single pole, one double pole and 4 3-ways.
Don

well i would like to thank all of you for you help on this matter, it is greatly appreciated

strokezilla,
Did any of the students solve this and get extra credit?
Don

not to my knowlage, i ran out off time after my last hands on final, i only had enough time to get all my boxes up and run all my wires didnt have enough time to wire all the fixtures and switches wish i had about a hour more and i think i could have gave it a run

Here's a little diagram:


Simple yet effective.

{Message edited to fix up link.}

[This message has been edited by Trumpy (edited 10-01-2005).]

Hmmm..... That gives you one light at a time.


The way I understood the problem is that you have six lights, each with a switch on the wall below and that at any one point in time you have two lights illuminated.

So if, say, lights #2 and #3 are on when you throw the switch at #3 you turn off light #2 and simultaneously turn on light #4. Then when you reach #4 throwing that switch will turn off #3 and turn on #5, but #4 will stay on.

It's easy to do with just simple 3-ways at each point if you use the "illegal" method.




[This message has been edited by pauluk (edited 10-01-2005).]

Paul,
It can be done in a code compliant manner.
Don

I got in a legal method, but screwed up....

I have "On - through - Off - On - Back through - Off"
http://www.markhellerelectric.com/tunnelsw.pdf

I messed up on "through twice", and there is a way to do it like this by moving the combinations around. But it hurts your brain after a while....

I get enough of that at work!

This is a complicated set of switching for what it is... But there is a way to do it to cover the combo of "On - through - Off - On - Back through - Off" And, "Through Twice"

The first switch is a single pole, switches 2-5 are 3 ways and switch 6 is a double pole. Hot to switch 1 and the switch leg to common of switches 2 and 3. One "taveler" from switch 2 to light 1, the other to the common of switch 4. One traveler from switch 3 to light 2 and the other to the common of switch 5. One traveler from switch 4 to light 3 and the other to the first pole on switch 6. One traveler from switch 5 to light 4 and the other to the second pole on switch 6. The switch leg from the first pole on switch 6 to light 5 and from the second pole to light 6.
Don

Don, I can't believe you beat me to it. I just sketched it in cad and emailed it to Scott35 to see if he could post it for me. Gotta be quick around here.

Ther only problem with this arrangement is that having gone through the tunnel one way it will then only work for the return trip.

You can't go through the tunnel twice in succession in the same direction.

Makes it easier to understand why they invented motion sensors ;-)

The lights follow you wherever you go at my house, inside and out.

*** BUMP + FYI ***

I have posted an ECN Member submitted Schematic, regarding this topic, in the Technical Reference section.

Look for it under the Topic Heading:

Lighting A Tunnel

(p.s.: You may click on the "Blue Underlined Text", which is a Hyperlink that will open the referenced page + Schematic)

Scott35

Scott I remember ripping out my hair on that one. But I think in that one now posted you can go IN, and then Back Out, but no-one could follow you through in the same direction. Not that it was technically part of the original question, but there has got to be a way to do it? As we all know, if it aint idiot proof - someone will tell you its broke.