Lights and Sound: LED arguement. Maybe you can help?

LED arguement. Maybe you can help?

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URL: http://www.communitytheater.org/forum/forum_posts.asp?TID=3101
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Topic: LED arguement. Maybe you can help?

Posted By: Lima
Subject: LED arguement. Maybe you can help?
Date Posted: 4/06/08 at 11:39pm

Ok, so a few weeks ago I was rewiring an LED theater light's (well, I actually think it's a dance light, but we're using them as theater lights) plug, to change it from European to an Edison plug. (we buy our LED's in the UK b/c they're cheaper there.)

Anyways, I only have a vague electricity background so I pretty much guessed when my TD asked me if it mattered where I put the hot and neutral wires in the Edison plug. I said no, he said that was right.

I said it didn't, because the plug isn't a polarized plug, and it only matters if the light's plugged in and someone's messing with the theater wiring. Or so I thought.

Because the other day I was rewiring a Stage Pin plug (on a traditional Fresnell), and my TD told me it *did* matter which was hot and which was neutral, and that the only reason he had told me it didn't matter before was because the other light had been a LED.

So I tell my dad this last night (he's worked in theaters, and with electricity), and he says that it absolutely SHOULD matter which wire I put where in the LED's plug, because, by definition, electricity can only flow in an LED in one direction.

So now I'm really confused, and we haven't plugged in the LED in question yet, because the others we ordered haven't come in yet, so I'm worried that something'll short out when they do plug it in.

Can anyone shed some light on this conflicting information? Does it matter with LEDs?

Replies:

Posted By: Gaafa
Date Posted: 4/07/08 at 12:54am

Your dad is correct in as much a a diode only works in one direction and it is DC [Direct Current] but this polarity is from the step down transformer to normaly 12VDC that powers the electronic circuitry inside.

conventionally it is good practise with general power plugs to rewire in a set method. Because where appliances have a single pole on/off switch & on the power point you have plugged into, it is safer to have the switch break the Active [hot] circuit,instead of the Negative side of the power. Rendering the appliance safely switched off with only the negative circuit in tact.

However even though it is an AC [Alternating Current] circuit, the appliance will work no matter which way the power circuit is connected, if the wiring all follows the same conventional method, this makes it safer for everyone.

Here we use the MEN [Mains, Earth,Neutral] system the appliance plugs & the GPO [General purpose Outlet (power point)] are marked in the fixing cable connections and polarity assigned. with the GPO when looking at the outlet front, where you plug into, starting at 11 O'clock the outlet pin receptacles are remembered by the acronym of 'ANE' in a clockwise direction, which of course is anti clockwise on the back of the plug 3 pin connectors. And the Mains power is at 254VAC Single Phase.

But one thing that intrigues me your voltage is surely 120VAC & the Pohmy [UK] is normally 220/240 VAC? Unless you use them in series using a 'twofer'?

I also would think in theatre it would be generally safer to use an Earth conductor on all the lighting equipment, unless the unit is marked as being 'Double Insulated' & an Earth is not to be required &/or used.

DISCLAIMER;- As your Current is double to what it is here on a given wattage, I would suggest that any electrical work as a disclaimer is carried out by a qualified electrician.

It is not the Voltage but the Current that KILLS!

As an aside all Electrical work carried out here on Voltage pressure over 32 Volts, has to be performed by a Licenced Electrician, holding either a Full, Limited or Restricted Licence. This covers everything including changing plug tops. While this is a legal requirement under the Act, it is only now starting to be in forced, also under the State Health Act with minimum fines of $2000 per breach. Which is why I was prompted to start the Technical Advisory Pool to assist Community Theatre Groups, because at this time I believe I am one of about a handfull of fully Licence A grade Electricians working in both Pro & Am theatres within the State at present!

This has taken a lot of years pushing for all techies here to be Licenced, wether they recieve any payment for work or not.

So Lima after all that waffle if you have changrd out the power plug correctly as previously it should not be a problem! Have a look at the Rating Plate on the equipment & see if it is suitable to be used on your Mains Power, as it could be half of the operating voltage. In which case it would need to be placed in series with another Unit of similar operating voltage first {hence the use of a 'Twofer'?]

Well there is always the 'Bang' test, if you have your work checked out, pug it in, stand back & switch on!

-------------
Joe
Western Gondawandaland
turn right @ Perth.
Hear the light & see the sound.
Toi Toi Toi Chookas {{"chook [chicken] it is"}
May you always play
to a full house}