LEDs on AC mains

[canman]

Wow, didn't expect this much discussion...I realize this topic is way off the guitar pedal topic and I apologize.

A few things...I understand the nature of AC, and the alternation between hot and neutral.  I also understand, as RG said, that only the electrons know which wire they're in.  So it follows that I understand some of the basic safety measures.

However, now you guys have me worried I did something wrong!  Let me explain what I'm working with here...the application doesn't matter, since I know you guys will probably say "why do you need that, anyways?"  I have a three conductor power cable connecting to two AC receptacles (the snap-in kind from Mouser) via an illuminating switch.  The hot wire from the main goes to one lug of the switch, and then the middle lug of the switch connects to the hot lug of the AC receptacle.  All the neutral connections are connected (obviously) and naturally, all the ground points are connected.  I did a lot of reading about switching with AC and the consensus was to only switch the hot signal. 

I soldered everything up, and the switch function works, and everything I plug into the AC receptacles work (it's in a plastic hammond box).  None of the connections are shorting each other out.  The only problem I can't figure out is the illuminating switch, as it won't light up.  Here's the scheme from the datasheet:



But other than that, am I missing any safety precautions?  All the wires are clear from each other, and the connections are all very solid.  There are little indicators on the AC receptacles that said neutral and ground (made my life easier, haha).

[R.G.]

Well at least in europe, the wall plugs are three wire and omnidirectional, with earth on the outside:

Yep. That's certainly true for some values of "in europe".      The reality is that each country, and sometimes different sections of the same country, have different types of AC mains plugs. There are many different "standards" of AC wall plugs, as can be seen in one reference: http://en.wikipedia.org/wiki/AC_power_plugs_and_sockets. For instance, here are two British plug "standards":



where ground, line and neutral are heavily differentiated. Although I'm sure that there are also differences of opinion about whether the UK is Europe or not.    

The plug you illustrated is the German "Shuko" type. France does this:


Actually, there is a German/French plug that simply ignores safety ground entirely, even if it's there, and male or female:


And here's an Italian "I'll take on any plug you got!" socket:


The "standard" for an area usually depends on the history. At some point, electrical power was wired to an area, and the provider often used an eccentric or deliberately different plug to force people to use their power, or to sell plugs; there are also other reasons. Once the local "standard" was set, history progressed, but the economic value of making new plugs be minor variations of the older and eccentric plugs was recognized. That's why travel plug converter sets are so popular - they let you use the electricity from the mains without having to buy new devices to fit the plugs.

Still, the electrons know which wires they're in. If one of the AC mains wires is "neutral" and attached to safety ground back at the distribution box, one of the two wires in the AC mains cord will be within a few volts of earth ground, the other will be at full mains voltage. If the mains voltage is symmetrical about ground, they are much more interchangeable, and both equally dangerous. And if the AC cord allows flipping omnidirectionally, they are both to be considered live and dangerous. There are just more ways to be deadly if they're omnidirectional.

Then there are other countries. Here's an excerpt from the notes on Brazil

Brazilian standard NBR 14136 (Type N)

Brazil, which had been using mostly Class II Europlugs, and NEMA 1–15 and NEMA 5–15 standards, adopted a modified (non-compliant) version of IEC 60906-1 as the national standard in 1998 (revised in 2002) under specification NBR 14136.[37] These are used for both 220 Volt and 127 volt regions of the country. There are two types of sockets and plugs in NBR 14136: one for 10 A, with a 4 mm pin diameter, and another for 20 A, with a 4.8 mm pin diameter, the latter used for heavier appliances such as microwave ovens.[38] NBR 14136 was not enforced or encouraged in that country until 2007, when its adoption was made optional for manufacturers, becoming compulsory on January 1, 2010. It helped domestic consumers that most of Class II plugs fitted in the new NBR 14136 sockets. However, very few private houses have an earthed supply, and even if a 3 pin socket is present it is not safe to assume that all three terminals are actually connected without testing. Most large domestic appliances are sold with the option to fit a flying earth tail to be locally earthed, although many consumers are unsure how to use this and so it is not fitted, effectively using the equipment as class 0.

[antonis]

Actually, there is a German/French plug that simply ignores safety ground entirely, even if it's there, and male or female:

Yeeepp...

It just serves for plugging in standard "shuko type" wall socket without the need of an adaptor...

(maybe you should put the blame on equipment's manufacturers for not grounding their instruments - if they violate the respective standards..)

[PRR]

Garrrrgh..... doesn't anybody remember how to wire a lighted switch?

The innernets isn't helping.

For the *simple* self-powered switch, the wiring is like this:



Obvious once you see it. Two lugs make/break power to your gizmo. Also to the inboard lamp, but it needs to return to the other side of the line, which is not needed on simple 1-pole power switching without onboard light.

For the specific goal (switched 'wall'-outlets), the "gizmo transformer" is replaced by your wall-outlet array.

I must point out that switched outlets can be *bought* factory wired and nominally safety-approved, at least in most jurisdictions. In the US it is common for them to have neon power lights. While cheap power strips are crap and I have resorted to DIY, I would rather let someone else take the pain and the blame.

Ideally the inboard neon resistor matches your line voltage. If you run a 115V-market switch in a 230V land, the neon and its resistor will burn-up fast. If you run a 230V neon in a 115V land, it will probably work dimly, maybe long life, maybe short life (current too low for cheap electrodes).

BTW: if you live long enough, neons die before you do, sometimes before the gizmo's useful life ends. I have several rugged power strips and one vintage clock which flickered for years and now only blip on power-spikes.

Also if the guy who comes after you (could be you after you forget what you did) has to replace this switch, the third wire to the other side of the line invites an "exciting" screw-up.

IMHO, for the usual case of a gizmo (amp, pedal, radio..), it would be much wiser to go over to the gizmo, find some 9V or 24V in there, and hang an LED (with resistor) across it. LEDs last much longer (they do not rely on a pinch of radioactives to get started). LED on the low-volt side has an obvious wiring. The power-switch and the power-indicator can be replaced separately, without needing special feature.

[PRR]

IMHO, the Shuko is the only honest connector. Clearly you can put it in either way. You have a good chance that Ground/Earth is where you expect, but usually have NO expectation where "hot" and ""neutral"" are.

> British plug "standards"... where ground, line and neutral are heavily differentiated.

It appears it can only be put-in one way. But from what I see of the inside wiring, it relies on the wirer to observe the color codes and faint marks on the device. The UK Hot/Cold colors ARE very distinctive. However I know the very clear US colors are routinely mixed-up in practice, especially by un-trained muckers. And it is a chain: it may be correct color at the outlet but swapped at the fusebox or any junction box along the way. I have seen it swapped *twice* so the outlet was correct but an intermediate run was wrong.

I wondered if UK wiring was so strictly enforced that nobody ever did it wrong. Or maybe the plug-guts are so clear that only an idiot could get it wrong. In fact the most common UK plug, remember the Blue takes a hard-Left, green goes to the odd pin, which leaves brown to the fuse. But I find other UK plugs with inline layout. I find plugs with wire-colors printed on them, but so small that I can't read them. And I found sites like http://eleksafe.co.uk/pat-testing/case-studies/ with pictures of major screw-up UK plugs, so even UK wirers are human. 

That's on top of the fact that the ""neutral"" is NOT a neutral and NON-NOT ground at the outlet. In my far-out house, G and N are bonded at the pole and the box, and there are dirt-rods, but "neutral" routinely runs 1V to 5V off of local dirt due to line-drop in my too-long line (and poor dirt conductivity). While 1V-5v isn't generally fatal, it screws-up any assumption that "white is grounded". In particular, the white-green current is not much limited, so a white-green short could weld thin metals (chassis, EMT, junction boxes).

And there are power systems where neither side is bonded to ground. Not just the US 240V center-tap, which does return to a ground. Both-wires-live is not normally found in residential power, but can happen if someone screwed-up.

There is also the Loose Neutral problem. In US 240VCT this can give a 80V:160V split with a large and floating white-green voltage. In 230V-only supply it can appear the whole house is "dead" but all the neutrals are 230V to dirt or plumbing.

While I observe convention, I always assume BOTH non-ground wires are HOT. Typically one much more than the other, but I do not *know* which it is.

[canman]

Obvious once you see it. Two lugs make/break power to your gizmo. Also to the inboard lamp, but it needs to return to the other side of the line, which is not needed on simple 1-pole power switching without onboard light.

OK...I think I almost understand what you're saying, haha.  "Two lugs make/break power to your gizmo."  That part I get.  "Also to the inboard lamp, but it needs to return to the other side of the line" is where I'm getting hung up.  This can't mean lugs 1 and 3 are connected, right?  Because then the switch wouldn't be much of a switch anymore...I guess the question is, what is the "other side of the line?"

Thanks for all the help...AC is wild.

[PRR]

> AC is wild.

"AC" is not the issue. Except that BIG (wall-power) AC can burn your house down, leave your dog homeless, so you can NOT afford to mess-around.

But the principle is the same for small and/or DC switches and lamps.

How would you do it for a 9V pedal?



One (+) 9V wire comes to the switch. Switch makes/breaks the connection. Past that you connect your gizmo, pedal-guts or whatever, from switched + side to the - side of the power. You would connect your resistor and LED the same way, from switched + to -.

If your lamp is built inside the switch, the switch maker will not give you four terminals (2 switch, 2 lamp) because one side of the lamp always connects to one side of the switch. Hence 3 terminals.

One difference is, in audio, we tend to have one side of the power also be connected to "audio ground". In wall-power wiring we have two "live wires" and *we* do not connect ground to either one (that has to be done ONE place, at meter or fusebox). So the green wire never goes near the wall-power switch or 120V/230V lamp.

And when messing with wall-power, NEVER GUESS, never exceed your sure-knowledge. In your case, if this switching isn't already very clear, add an extra outlet and shove a night-light in it.

[greaser_au]

And it is a chain: it may be correct color at the outlet but swapped at the fusebox or any junction box along the way.

I have lived in rural Australia and the supply authority has screwed it up at the top of the pole more than once!!!!

I wondered if UK wiring was so strictly enforced that nobody ever did it wrong. Or maybe the plug-guts are so clear that only an idiot could get it wrong. In fact the most common UK plug, remember the Blue takes a hard-Left, green goes to the odd pin, which leaves brown to the fuse. But I find other UK plugs with inline layout. I find plugs with wire-colors printed on them, but so small that I can't read them. And I found sites like http://eleksafe.co.uk/pat-testing/case-studies/ with pictures of major screw-up UK plugs, so even UK wirers are human. 

The 240V places are usually a bit stricter. In a single-phase installation (normal household power supply), the neutral is grounded (Multiple Earth Neutral). Usually the plugs are marked with standard colours or A/N/E, so it is difficult to screw it ip without really deliberate stupidity.

I understand that the usual US deployment has 2 phases that swing either side of the neutral?

david

[R.G.]

I understand that the usual US deployment has 2 phases that swing either side of the neutral?

The US supply is also 240V, but this is center tapped on the power pole. The feed to the house is three wires, two "balanced" 120V wires and a center tap that is grounded at the power pole.

The center tap is again earth-grounded at the distribution box inside the house, and the two 120V "phases" are then used to power outlets, lights and appliances. The heavier appliances, like ovens, clothes driers, and air conditioners, are fed both 120V phases to get 240. Normal outlets are fed only one 120V phase and "neutral", which is the center tap from the power pole, which was re-grounded in the distribution box, and carries return current, and a safety ground wire from the distribution box that is not supposed to carry current except for fault currents if they happen.

[canman]

So, PRR...the basic idea is to just jumper terminals 2 and 3, since the resistor is internal?

I understand AC is not the issue.  I'm just making the statement that AC is wild.  DC is just as wild...just easier for me to understand and work with.

[Jdansti]

You need a path back to the power station from the internal light so that you'll have a complete circuit. This is done with the neutral wire.  Connect the hot (usually black) to lug 2, the neutral (usually white) to lug 3, and the gizmo you are powering to lug 1. If the switch has a ground lug on it, connect the safety ground wire (usually green) to it. Heed all of the precautions mentioned by R.G. and the others.



Edit: the above assumes 120V mains service, appliance and switch. 240V would be similar, but you would have two "hot" wires (one connected to lug 2 and the other to lug 3) and no "neutral".

[antonis]

The heavier appliances, like ovens, clothes driers, and air conditioners, are fed both 120V phases to get 240.

(just for info..)

Is there neccesity for any modification on wall sockets for getting 240V or are there "prefixed" outlets therefor...

[R.G.]

Is there neccesity for any modification on wall sockets for getting 240V or are there "prefixed" outlets therefor...

There are dramatically different outlets for the single-side 120Vac outlets and the two-side 240V outlets. It is functionally impossible to insert a 120Vac plug into a 240Vac socket and vice versa.

The standards for AC power wiring are such that wiring 240Vac to a normal 120Vac outlet is forbidden, and most local governments require electrical safety inspections before allowing occupation of new construction. So the few places in a house that get 240Vac are specially wired, and have special 240Vac only outlets.

If you're interested in the topic, here's one guide to outlets around the world:
http://www.interpower.com/ic/guide.html
Wikipedia has neato pictures.
http://en.wikipedia.org/wiki/AC_power_plugs_and_sockets

[canman]

You need a path back to the power station from the internal light so that you'll have a complete circuit. This is done with the neutral wire.  Connect the hot (usually black) to lug 2, the neutral (usually white) to lug 3, and the gizmo you are powering to lug 1. If the switch has a ground lug on it, connect the safety ground wire (usually green) to it. Heed all of the precautions mentioned by R.G. and the others.



Edit: the above assumes 120V mains service, appliance and switch. 240V would be similar, but you would have two "hot" wires (one connected to lug 2 and the other to lug 3) and no "neutral".

This. is. AWESOME.  Thank you so much!! 

[PRR]

> 240V would be similar, but you would have two "hot" wires ...and no "neutral".

UK/Euro 230, one side is probably connected to a street-level neutral which is safety-bonded to street dirt (usually house-dirt as well).

If UK plugs are correctly wired, you know which it is. On most Shuko plugs, you do not.

Inside applances, you should not need to care which is which. Two black wires, either one live-to-ground, is as good as any other scheme.

Edison-type screw base lamps, we really-really should try to get the less-hot wire to the shell, so that a loose bulb is not a 117V shock through user to plumbing or dirt. This is a fault of this type lamp. (Some decades back they raised the outer shell; I remember sockets where the shell was exposed.)



> 2 phases that swing either side of the neutral?

Tommy Edison's original (DC) power system was +100V, zero, -100V. Zero was grounded and Tommy felt that 100V to ground was not too dangerous (remember good rubber had not arrived). Lamps were wired to one side or the other. If the load on both sides balanced, the zero wire current cancelled ("Neutral"); worst-case a 100V and the zero wire ran warm and the other 100V wire ran cold. Twice the power (and twice the billing) for only 1.5X the copper cost and still "safe" voltages to ground.

The bulk of UK/Euro electricfication happened after good insulators, but with high copper cost, so voltages are higher. UK/Euro do the same multi-wire thing except it is 3-phase power in the street and 1-phase power to most buildings. Houses are staggered over all three phases, so on-average the Neutral wire carries less current. Inside the house the voltage is as expected; but if you run long meter wires to compare your 230v Hot to your neighbor's 230V Hot you are liable to find 400V. (Large facilities get all three phases and can tap large 400V loads directly; such service is also common in US main streets and available to large US customers.)

Another part of the differences: UK/Euro customers tend to be "compact". Many customers in a small area. Urban US is similar, but we have a LOT of low-density development, many miles of wire for very few customers. Then the economics shift to very high voltages for the long-run, dropping to low voltage for each few customers. While UK/Euro wiring must do the same thing, there are generally many-many customers per drop-down transformer; here we may have two houses on one 6,000V:240V transformer.



> modification on wall sockets for getting 240V

There are small US 240V outlets which look a lot like 120V outlets, but the 120V plug can not be forced into them. Several odd sockets were used until 1950. Mostly we only take 230V for LARGE loads with large sockets. My lamp outlets are a little over an inch, my stove or clothes-dryer outlet is 3 inches round, no confusion. IOW, two 120V taps fit in a 2"x4" box, a modern 230V stove/dryer single tap mostly fills a 4"x4" box. 

[Brisance]

In europe, at least in scandinavia, and baltics, the 240V is a live + neutral, but for large ovens etc we get three phases, a neutral and a ground, adding up to 330 or 380V in plugs like this:

There also was an older style plug in ex-soviet countries, which I cannot find a picture of.