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Effects control

Discussion in 'Special Effects' started by jacobbiljo, Mar 21, 2006.

  1. jacobbiljo

    jacobbiljo Member

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    just thought id ask how people control their special effcets such as a disco balls or normal flouresent tubes, anything elctronically controled. our theatre doesnt have the capability to use our dimmers as relays so weve rigged up control wires in the audio snake (until we run a seperate line) to control a 12v PLC which then controls 120 v relays. Weve built a nice box for it and it is powered by a 240 volt plug so we can run about 4 120v circuits plus 12 v circuits without any concern about blowing fuses. Its a pretty advanced selfmade solution and its only because im very comfortable with electronics and the other guy involved with any type of effects is an elctrician.

    We used to use a simple switch board (made of normal household light switches) controled by a stage hand via instruction over headset from the booth. After a bad preformance where it took almost a minute before the stage hand responded to his cue, we decided we needed control from the booth and rigged this up for the next nights show.

    I was just wondering how others manage
     
  2. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    FX lights or anything else with a transformer is controlled via a switch pack. I have a 6ch rack mounted one as well as a 4ch stand alone one.

    The idea of low voltage to switch high voltage is a good one given that you are using a snake to do so. Keep an eye on those relays however, as over time the contacts will arc and burn out. Opto isolated triac control would be the optimal but is a lot more complicated in terms of construction, although not that much more expensive and will last forever (well almost). Did you use PCB mounted relays or did you get the ones that plug into a socket? The latter will certainly make it easier to swap out bad relays.

    Talking about relays - I actually have a 2ch lighting controller that uses a DPST relay to switch between two lighting circuits. It is controlled by 12V signal that is switched by a guitar foot switch (like the ones to switch between clean/dirty on some amps). I hire it out to small bands that want to have a stage wash but don’t have a lot of money. This way, one of the band members can switch between a cool or warm wash by stomping on the foot controller. This will only work with a DPST (5pin) relay though, as you need one circuit on the NC and the other on the NO. Energizing the relay coil takes the power from the NC and connects it to the NO

    Given that you are only switching on and off the power to such items and that you are not doing it all that frequently (i.e., trying to strobe a pinspot) there is no reason that you couldn't use a house or other mains voltage rated switch. I would place a fuse or breaker on each individual circuit though, as well as a master fuse/breaker.

    The first one that I built was the 4ch one and that uses standard house lighting switches.

    I would strongly advise getting anything that is built "in house" looked at by an electrician to determine that it is safe in construction and application.
     
  3. ship

    ship Senior Team Emeritus Premium Member

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    Second Mayhem's advice but in general think what you have in mind is some good solutions or concepts.
     
  4. AVGuyAndy

    AVGuyAndy Active Member

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    On our (very) old school board, there is an undim secion which is just on off realy control for 6 channels. I put spots and sometimes power for backline on there.
     
  5. jacobbiljo

    jacobbiljo Member

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    we now also have a switching box connected up to half of our dimmers that allows us to switch between 2 completly seperate wiring layouts. this again is controlled by 12v relays but we have not had a use for is and have not yet adapted it to be controled from the booth via the snake, or be controled by any matter so far. It is a self made box by our lighting installer who recently took it out of a dinner theatre which needed it to switch between two seperate show's lighting schemes which each had their own individual sets of lights.
    as of now, we have used the plc to simply give us the 12v power, provide diagnostics lights, a key lock off, variable 12v power for our disco ball and and switch on the relays. These are bolt down type (non socket) relays as i dont personally like using veroboard anywhere near 120v mains.
    our theatre is running on a 0-10v control system so we dont have the luxury of a commercial dmx switching system
    i do agree with mayhem in that anything involved with 120 volts should be looked at by an electrician, but for us, considering my partner is about 2 months away from being a fully qualified electrician and his dad is an electrician and owner of a big commercial electricians company, we do not have that concern. The use of fuses on our original control baord was not much of an option becuase this was built before my time in the theatre, just like all other devices built by my predesesor, the board has been retired.

    a question for mayhem, were you implying on going back to our old system of having someone physically switch a switch, because we have wanted to get rid of this because of shoddy stage hands and the distance problem with running 120volt wires back into the booth.

    This was orginally just a question for others, to find out what they use for controling anything other than lights.
     
  6. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    No - not at all. I think your current situation is a good one and the use of 12V control down the snake is a good way of using this system to meet your needs.

    My comment about the household switches was just to say that it is a safe and usable alternative for anyone who didn’t wish to make a 12V relay system. I certainly wouldn’t suggest going back to a system that didn’t work for you when you have a good one in place that does the job and eliminates the need for additional steps (i.e., cue the stage hand).

    The rest of my post was answering the question of what I use for switching on items that either do not require dimming or are not suitable to run from a dimmer.

    The relays and sockets I spoke of were not the ones that are pcb mounted but rather the socket is bolted to the inside of the box and either has spade connectors or screw down terminals for wiring purposes and then the relay is inserted into that. But in my experience, there is no problem with running 120V on veroboard. I have been using a 24V reticulation timer to switch a 240V bore pump on for over five years and it never had a problem. In summer it turned on and off twice a day, two days a week (sold that house).

    However, switches and relays are mechanical devices and will wear out over time. This is why my next project will be a triac driven switch pack. Circuitry shouldn’t be too hard to figure out and will also be used on a mains load cable tester (only once it has passed a continuity and insulation test at low voltage).
     
  7. jacobbiljo

    jacobbiljo Member

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    the one problem which i have been informed of with the use of triacs, is that they are not compatible with flourescent tube ballasts, even when simply used as switches. do you know if this is true? our theatre uses many of these for things such as blacklights and even sometimes when in a bind, for normal stage lighting
     
  8. soundop

    soundop Active Member

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    we have to make do with every day items
     
  9. jacobbiljo

    jacobbiljo Member

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    so what are those everyday items you make do with?
     
  10. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    From my understanding there should not be any problem when using triacs as a switch when separate from a dimmer. I have never used a dimmer where a channel can be set to switch on/off rather than dim, but I have seen discussions where this was discussed as the power was still routed through the dimming circuitry. Now I don’t know what the difference is other than a possible phase shift or maybe the effect of a choke.

    However, a trial is essentially a solid state relay but without the mechanical components. Provide a trigger voltage, and it allows the mains voltage to flow through it. Remove the trigger voltage and it stops the mains voltage.

    To make it safe, you supply the trigger voltage via an optocoupler, which is activated by a low voltage source, such as you are currently using to trigger your relay.

    The optocoupler is actually a LED and a light phototransistor receiver (PTR) combined in one package. The LED is switched on by the low voltage control circuit and the PTR feeds the mains voltage into the triac.

    Because it is light that makes the optopcoupler work, it provides a physical barrier between the high voltage power circuitry and the low power control circuitry. Hence the term opto-isolation. HERE is a .pdf document on Optocouplers and fig.8 on page 2 is the circuit to use for a trial switch. I just need to find the time to sit down and work out the component values!
     
  11. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Wow. Those are some cool ideas. I've typically used a 100 foot extension cord and a kid with a walkie talkie... but you system sounds a little more reliable.
     

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