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System for switching circuits of high-wattage devices

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.

Reply to
DJ Craig
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--- 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-->\ \ --------+----------+-------------+-----+

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 \K2A /K1B /K2B ----|------------------------+ | | | | | N2>----+------------------------------------+

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

-- John Fields Professional Circuit Designer

Reply to
John Fields

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

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Reply to
me

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
Reply to
Vidar Løkken

Can anybody tell me what I'm missing or doing wrong? When schematic are shown in posts, I only see meaningless stuff like

L2>----+----------------------------+

| | | | L1>----|----------------+ | | | | O-->\ \ --------+----------+-------------+-----+

Apparently the rest of you can see a schematic diagram. What do

need or have to do to see the actual schematic? (Do you see schematic above or a meaningless 13-line listing starting wit L2>, and ending with "NEUT> followed by a dashed line with signs and ending with a +?

Thank

awrigh

Reply to
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.

Reply to
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

Reply to
redbelly

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