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Author Topic: Spontaneous Reversal of Wires????  (Read 9488 times)

Mike Sokol

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Re: Spontaneous Reversal of Wires????
« Reply #10 on: May 08, 2014, 03:32:02 pm »

Tracing it out is easy-just not in my head after spending the afternoon in a 110 deg greenhouse.

Normally 1 and 3 should be lit.

Open neutral only 3 would be lit.

If a load is plugged  in downstream of the open in the neutral then 2 and 3 would be lit, which is the same result as if you reversed the hot and ground. 

Again, my first suspicion-partly because of the ease of checking for it, partly from experience would be push in wiring in receptacles.

One of the projects I've considered is a master "goof board" with every variation of mis-wired and open-wire recept/outlets possible. Then I could plug a 3-light outlet tester from recept to recept and demonstrate the light patterns. Or I could build a matrix with 3 x 3 relays that would use one duplex outlet that would be programmable for every possible wiring failure and mis-connection. I've got a little Rasberry PI by kids gave me for Christmas just begging for a project, so maybe that would be fun. Gotta remember to "break" the relays before the "make" since it could easily cross-connect the incoming wires if I'm not careful with the programming. Yeah, I'll put a series limiting resistor on each leg in case something goes wrong in my logic. I admit to being a hack at programming this stuff, so I need a backup plan. 
« Last Edit: May 08, 2014, 03:51:55 pm by Mike Sokol »
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Tom Bourke

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Re: Spontaneous Reversal of Wires????
« Reply #11 on: May 09, 2014, 02:48:39 am »

Or I could build a matrix with 3 x 3 relays that would use one duplex outlet that would be programmable for every possible wiring failure and mis-connection. I've got a little Rasberry PI by kids gave me for Christmas just begging for a project, so maybe that would be fun. Gotta remember to "break" the relays before the "make" since it could easily cross-connect the incoming wires if I'm not careful with the programming. Yeah, I'll put a series limiting resistor on each leg in case something goes wrong in my logic. I admit to being a hack at programming this stuff, so I need a backup plan.
No way I would use a Pi for this application.  The Pi is like a late 90's computer with a modern low end video card. Way over kill and complex for the task at hand. If it MUST be chip and relay driven, with minimal programming knowledge, then use an arduino variant.
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Mike Sokol

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Re: Spontaneous Reversal of Wires????
« Reply #12 on: May 09, 2014, 06:51:13 am »

No way I would use a Pi for this application.  The Pi is like a late 90's computer with a modern low end video card. Way over kill and complex for the task at hand. If it MUST be chip and relay driven, with minimal programming knowledge, then use an arduino variant.

Very interesting. A quick search found an 8-channel Arduino output interface with 10-amp relays rated for 250 VAC. Cost is $19.59 with free shipping to the USA. I can't buy just the relays for that kinda money. http://www.dx.com/p/arduino-8-channel-12v-relay-module-expansion-board-142797#.U2ywpijVvpc

Gosh, I think this controller needs 9 relays for the outlet goof matrix, so perhaps I should do a Karnaugh Map and try the simplify the circuit a bit. I used to do Karnaugh Maps all the time in the 70's while designing relay logic for packaging machines. It's been a long time, but I'm betting it still works...
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John Roberts {JR}

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Re: Spontaneous Reversal of Wires????
« Reply #13 on: May 09, 2014, 08:52:39 am »

A few knife switches and fuses....

Programming an embedded controller only makes sense if it needs to be automated or make decisions based on reading conditions.

JR
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TJ (Tom) Cornish

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Re: Spontaneous Reversal of Wires????
« Reply #14 on: May 09, 2014, 09:02:54 am »

A few knife switches and fuses....

Programming an embedded controller only makes sense if it needs to be automated or make decisions based on reading conditions.

JR
Half of the world's new inventions are made because they're cool, not because they are necessary or the simplest way to do something.  I think Mike was going for the automatic interlock element - the micro automates opening and closing so you can't goof the switches up.

Unless the Frankenstein element of knife switches is what you're going for, it seems foolish to use them at line voltage. A dual throw with center off switch would seem safer.
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Steve M Smith

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Re: Spontaneous Reversal of Wires????
« Reply #15 on: May 09, 2014, 09:15:36 am »

I used to do Karnaugh Maps all the time in the 70's while designing relay logic for packaging machines. It's been a long time, but I'm betting it still works...

No.  Everything has to be done with computer simulation and CAD, CAM and 3D modelling now - just ask any of the cool kids!


Steve.
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BobWitte

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Re: Spontaneous Reversal of Wires????
« Reply #16 on: May 09, 2014, 12:27:04 pm »

Very interesting. A quick search found an 8-channel Arduino output interface with 10-amp relays rated for 250 VAC. Cost is $19.59 with free shipping to the USA. I can't buy just the relays for that kinda money. http://www.dx.com/p/arduino-8-channel-12v-relay-module-expansion-board-142797#.U2ywpijVvpc

Gosh, I think this controller needs 9 relays for the outlet goof matrix, so perhaps I should do a Karnaugh Map and try the simplify the circuit a bit. I used to do Karnaugh Maps all the time in the 70's while designing relay logic for packaging machines. It's been a long time, but I'm betting it still works...


VERY LOGICAL!

Mike Sokol

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Re: Spontaneous Reversal of Wires????
« Reply #17 on: May 09, 2014, 02:12:57 pm »

Unless the Frankenstein element of knife switches is what you're going for, it seems foolish to use them at line voltage. A dual throw with center off switch would seem safer.

As much as I love big knife switches, putting line voltages on them and flipping around in a demonstration is probably a little over the top. One easy(er) way to do this could be relays and diode logic on a rotary selector switch. I worry about the break-before-make time of the matrix relays though. I just don't want to haul around a huge demo board with a few dozen outlets in various states of mis wiring. Not elegant enough and takes up too much room in the pack. Ideally this this be in a little quad box with some sort of remote controller.

Just dabbling with how to even do this is fun. I think showing all the ways that 3-light outlet testers can mislead you would be highly instructive.
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Mike Sokol
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Mike Sokol

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Re: Spontaneous Reversal of Wires????
« Reply #18 on: May 09, 2014, 02:23:07 pm »


Just dabbling with how to even do this is fun. I think showing all the ways that 3-light outlet testers can mislead you would be highly instructive.

How about 3 rotary switches with 4 positions each. So each of the 3 contacts in the duplex outlet could be switched to H-N-G-X

That would be foolproof and pretty cheap to build, I think.
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John Roberts {JR}

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Re: Spontaneous Reversal of Wires????
« Reply #19 on: May 09, 2014, 03:49:14 pm »

Yup KISS....  I actually gave some thought to designing a smart outlet strip that would sense the mains connections and self correct if needed, but not really a viable product.

JR
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Re: Spontaneous Reversal of Wires????
« Reply #19 on: May 09, 2014, 03:49:14 pm »


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