System for switching circuits of high-wattage devices

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DJ Craig

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Jun 30, 2005, 1:18:41 PM6/30/05
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Forgive me if I've posted this message in the wrong group. I'm not
really sure where I should post this.

I'm a mobile DJ. I often DJ outside people's houses, or at hotels,
camp grounds, appartment blocks, churches, etc. These places usually
will let you draw about 2000 watts from one of their circuits before
you blow the circuit breaker. My equipment requires between 4000 and
5000 watts. The lighting effects, fog machine, etc, requires about
2000-2500 watts, and the audio equipment requires about 2000-2500
watts. I have about 1000 watts-worth of equipment that *must* remain
on througout the event, such as CD players, mixer, amp and speakers.
It is a nightmare trying to distribute my equipment across multiple
circuits so that I dont blow fuses, which I often do. It is not too
bad if the lights and fog machine turn off during an event, but it is
important that my audio equipment keeps running thoughout an event.

I thought that it may be possible to build a gadget that would hook
into 2 circuits, where i would plug my audio equipment into the
"reliable" plug, and the lighting into the "unreliable" plug. If
either of the two circuits blow, then the box would switch the audio
equipment over to the remaining circuit, and turn off the lighting.
Does such a gadget already exist, or would it be possible, and
practicle to build?

One issue is that if my CD players are turned off, even for an instant,
the music will stop and I have to re-cue the music. So a box that just
uses a relay to switch the circuits may not work. I'm not sure, but
the CD players may not be able to handle the delay caused by the relay.
Especially if the voltage from the circuit that is blowing fades
before it goes right out, creating even more delay and causing the CD
player's condensers to empty. Could it be done with a triac instead?
Would a triac be able to handle the high wattage?

Can anyone think of another solution to my problem? I always try my
best to hook into as many circuits as possible, and distribute my
equipment evenly, but I still have trouble.

John Fields

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Jun 30, 2005, 3:10:37 PM6/30/05
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On 30 Jun 2005 10:18:41 -0700, "DJ Craig" <sp...@djtricities.com>
wrote:

---
I like the relay idea to switch the lights and audio stuff, but I'd
get an uninterruptible power supply for the CD players and wire its
input to the audio side of the relay. That way, even if you lose
power and it takes the relay a few tens of milliseconds to switch the
audio stuff to the good line, the CD player would have power supplied
to it all the time and it would just keep playing.

I'd use a DPDT relay with contacts rated for 30 amps and hook it up
like this:

L2>----+----------------------------+
| |
| |
L1>----|----------------+ |
| | |
O-->\ <--O O-->\ <--+
NO \ NC |NO \ NC
O | O--+----[AUDIO STUFF]
| | | |
[LAMPS] [COIL] +--[UPS]---|---[CD PLAYERS]
| | | |
| | | |
NEUT>--------+----------+-------------+-----+

That way, when you plug the thing into line 1 (L1) the relay coil
(120VAC) will be energized and will cause the common contacts to move
over to the normally open (NO) contacts. That will cause the lamps to
be connected to L2 and the critical stuff to L1.

Now, if L2 drops out the lights will go out, but the critical stuff
will keep going. However, if L1 drops out the coil will no longer be
energized, which will cause the common contacts to fall back on the NC
contacts. That will disconnect the lamps from L2 while connecting the
critical stuff to L2, and the UPS on the CD players will keep them
from getting the slightest hint that anything happened, which is what
you want.

There is one small snag though, and that's that there's no guarantee
that neutral and hot won't be reversed on on of the sockets you plug
into, so uless you keep everything separate, nasty shit could happen.
Fortunately, there's an easy way out and that's to use another relay
to switch the neutrals, like this:

L2>----+----------------------------+
| |
| |
L1>----|----------------+ |
| | |
O-->\K1A <--O O-->\K2A <--+
NO \ NC |NO \ NC
O | O----+----[AUDIO STUFF]
| | | |
| +--+----+ | |
| | | | |
[LAMPS] [COIL1] [COIL2] +--[UPS]---|---[CD PLAYERS]
| | | | |
| +-------+--------+-+-----+
| |
O O
NO / NC NO / NC
O-->/K1B <--O O-->/K2B <--O
| | |
N1>----|------------------------+ |
| |
| |
N2>----+------------------------------------+

A good relay would be an OMRON MGN2C AC120, $29.70 each at Digi-Key.

--
John Fields
Professional Circuit Designer

me

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Jul 1, 2005, 8:54:43 AM7/1/05
to

>Can anyone think of another solution to my problem? I always try my
>best to hook into as many circuits as possible, and distribute my
>equipment evenly, but I still have trouble.
>


I find your power requirements unlikely at best. But if true, buy a
portable 5kW+ generator...

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Vidar Løkken

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Jul 1, 2005, 9:30:22 AM7/1/05
to

If you where to design anything, I'd suggest ensuring that multiple
outlets was right regarding to hot/neutral, and connect all of them to
the input of a UPS. Some of APC's UPSes accept multiple inputs,but they
weigh above 100kg, and costs accordingly, but provides power for a while...

--
MVH,
Vidar

www.bitsex.net

awright

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Aug 19, 2005, 12:35:17 PM8/19/05
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Can anybody tell me what I'm missing or doing wrong? When schematics
are shown in posts, I only see meaningless stuff like:

L2>----+----------------------------+
| |
| |
L1>----|----------------+ |
| | |
O-->\ <--O O-->\ <--+
NO \ NC |NO \ NC
O | O--+----[AUDIO STUFF]
| | | |
[LAMPS] [COIL] +--[UPS]---|---[CD PLAYERS]
| | | |
| | | |
NEUT>--------+----------+-------------+-----+

Apparently the rest of you can see a schematic diagram. What do I
need or have to do to see the actual schematic? (Do you see a
schematic above or a meaningless 13-line listing starting with
L2>, and ending with "NEUT> followed by a dashed line with +
signs and ending with a +?)

Thanks

awright

JeffM

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Aug 19, 2005, 3:00:23 PM8/19/05
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>When schematics are shown in posts, I only see meaningless stuff
> awright

Set your newsreader to use a monospaced font (Courier)
or cut the text
and paste it into a text editor that uses a monospaced font.

Many folks add a note to the ASCII art specifying this.

redbelly

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Aug 19, 2005, 3:30:04 PM8/19/05
to

JeffM wrote:

> Set your newsreader to use a monospaced font (Courier)
> or cut the text
> and paste it into a text editor that uses a monospaced font.
>
> Many folks add a note to the ASCII art specifying this.

I think awright's problem is that multiple spaces are being truncated
to single space by some editor used by his newsgroup service. In that
case, switching to a fixed-space font won't solve the problem.

The only solution I can think of is for awright to use a different
service to access newsgroups.

Mark

JeffM

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Aug 19, 2005, 10:35:36 PM8/19/05
to
>When schematics are shown in posts, I only see meaningless stuff
> awright

::Set your newsreader to use a monospaced font (Courier)


::or cut the text
::and paste it into a text editor that uses a monospaced font.

:: JeffM
:
:I think awright's problem is that multiple spaces


:are being truncated to single space
:by some editor used by his newsgroup service.
:In that case, switching to a fixed-space font won't solve the problem.
:
:The only solution I can think of
:is for awright to use a different service to access newsgroups.

: Mark (redbelly)

OK. Another idea.
Use this link
http://groups-beta.google.com/groups/dir?lnk=gh&sel=33580724
to access any of the sci.electronics.* groups from the Usenet Archives
(including the defunct sci.electronics.[nada]).

Bring up the thread, find the post, then click **show options**.
The **Show original** link will give a monospaced display
(including headers).
.
.
Another twist:
At the top of the Thread page is a **Fixed font** link.

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