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Control/Dimming Multi-port DMX switching unit

Discussion in 'Lighting and Electrics' started by wah0808, Jun 23, 2009.

  1. wah0808

    wah0808 Member

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    First let me say that I did do a search and didn't find anything that really resembled what I trying to do... or at lease what I searched on didn't lead me to anything that sounded too similar.

    That being said... Every two years I'm TD of an a community Ice Show. The lighting grid is permanently wired with 12 circuits, I have another 3 on the back wall and 3 colour 'bang boards' (ice level marker lights) giving me a total of 18 circuits. Currently these are controlled via two banks of relays connected to a switch box in the booth.

    Since introducing moving head lights a few years ago I now have two control units. One is my laptop via a usb to DMX interface and one is the antiquated control board (mentioned above) build before I was born...

    I'm looking to purchase (or plans to build) an 18 channel DMX controlled switch to replace the current board allowing me to control the existing relays. Everything I've found that is commercially available is a low voltage to high voltage relay (or dimmer), or is just a single switch; that would be rather expensive to replace 18 switches. Also seeing as this is a community skating club (and the show is every other year) I'm trying to do this on a reasonable budget.

    I have the relays I just want to replace the switches...

    Any ideas?

    Thanks...
     
  2. NickJones

    NickJones Active Member

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    So you are looking to DMX control them to control on your computer? This will cost you a few hunderd dollars and take a while. But can be cool if you can do it. If that is what you want to do, I'll give you a write up.
    Nick
     
  3. wah0808

    wah0808 Member

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    That is exactally what I want to do... Basically I have two goals, 1) replace the board of 18 switches, 2) control the moving head lights and relay switched circuits with one board (in this case my laptop, unless I grab a small board off ebay...)

    thanks,

    Alan...
     
  4. epimetheus

    epimetheus Well-Known Member

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    Occupation:
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    What's the coil voltage on the relays? If it's 48V DC or lower you could use one of these. I found these a few months ago and ordered one for some LED projects. I drive it with my laptop and BlueLite X1 Mini.

    If the coil voltage is AC, check this out.
     
  5. wah0808

    wah0808 Member

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    Interesting, I have to double check... but as far as I know one bank is 12V and the other bank is 24V ... So the first board may be the answer...

    Thanks!

    Alan...
     
  6. wah0808

    wah0808 Member

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    After another look at the circuit board I'm not sure that solution would work either. The voltage is already provided in my case... I'm just trying to control the closing of the circuit (ie. just replacing the switch) If I were to use that board I would have to drive another relay to act as the switch... not a huge issue I guess, but it seems like it's over complicating things...

    Please stop me if I'm missing something here. I may have to go back to the drawing board and try to trace exactly what I have. The setup at the arena is over 30 years old so there is no paperwork.

    I don't want to have to replace the relays and I'm certainly not looking at replacing the control cable (as it runs to the other end of the Arena).

    The idea is remove a switch and replace it with a DMX controlled switch * 18 ...

    The more I think of it the more the first solution with separate relays looks like the only answer.

    Alan...
     
  7. Footer

    Footer Senior Team Senior Team Premium Member

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    Whats the load on each of the relays? You might want to look into getting some shoebox dimmers, might be a cheaper solution.
     
  8. Dover

    Dover Active Member

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    Three of these DeMux units from MA Lighting would do what you want. The relay based version comes in a case or as a pc board that you would need to mount them in a case. I would recommend that you go with the pc board units and mount all 3 in the same case. It would make the whole system more reliable to have the connections in a case.
     
  9. wah0808

    wah0808 Member

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    That looks like it would do the job... Only question is how would one daisy-chain 3 together?

    Thanks.

    BTW...

    Here is an image of the switch board I'm trying to replace...

    [​IMG]

    Alan...
     
    Last edited: Jun 23, 2009
  10. epimetheus

    epimetheus Well-Known Member

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    That MA Demux unit is the same type of board as the Blue Point one I linked. If the relay coil voltage is DC you can use the first board I linked without any additional relays. The positive voltage from the system would connect to the LED+ input and the positive side of the relay coils would get commoned together and connected to system positive. The negative side of the relay coils would connect to the LED1 thru LED18 headers. The LED- terminal would then get connected to system negative.

    Whether you can use the 32 channel board I linked is really dependent on what the coil voltage is, AC or DC.
     
  11. NickJones

    NickJones Active Member

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    Looking at the photo you have no need to dim by looking at that, on older lighting consoles the board is plugged into the wall and by sliding up and down the faders you dim the 12v Output that goes to the dimmers. Can you get a voltameter on and find out the voltage (without killing youself) this will help. As for egtting them all linked, you may need a DMX splitter as most only have DMX inputs no DMX output and therefore cannot be dasy chaned input-output as most dimmers & MLs can.
    Nick
     
  12. NickJones

    NickJones Active Member

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    Presumabley this would be of some help to you, feed it between 7-15v depending on how much power you need, connect it to each of the relays & hook it into your DMX universe?
    Nick
     
  13. dramatech

    dramatech Well-Known Member

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    Occupation:
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    Check with Northlight systems. He has some funky email, but there are links somewhere on the CB forums, Or Google Northlight Systems in Tempe, Arizona. The website had several options, from DMX to relay, or DMX to Analog. once you find the website, call and talk to James Cart, tell him your problem and he will lead you in the right direction. He is the least expensive of all the circuitboard tye devices, and will give you very personal attention. I just looked up his number, and it is 480-429-0577. I have at least one of almost every board that he makes, and they are great and inexpensive.
     
  14. wah0808

    wah0808 Member

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    Not sure that I follow... I know I don't need a dimmer, hence the reason I asked if there was a DMX controlled switch. The board pictured is just a bank of switches, it provide no power at all to the relays it merely allows for completion of each circuit. The top row of switches open/close the 12V relay circuits in the booth, and the bottom row of switches open/close the 24V relay circuits at the other end of the arena.

    I think the solutions provided should work, I'll investigate further.

    Thanks,

    Alan...
     
  15. wah0808

    wah0808 Member

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    Excellent, I will look in to this... Thanks!

    Alan.
     
  16. epimetheus

    epimetheus Well-Known Member

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    The TTL outputs of the unit Nick linked will probably not be able to drive the relays directly. The relay coils would have to draw less than 20mA each. You need a board that can translate DMX to either relays or power transistors on board that will then drive your relays.
     
  17. wah0808

    wah0808 Member

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    Maybe I'm not explaining myself properly... Here is a simple schematic of what I have today...

    [​IMG]

    I just want to replace 'Switch A', everything else in the circuit should remain the same. The low voltage source is provided from a transformer located at the two relay banks (one 12V and one 24V) and not from the board (located in the booth). I didn't design this system, I'm merely trying to make it easier to work with. :)

    Maybe we are all on the same page and I'm just in a confused state (it happens from time to time). It's not like I don't have an understanding of electronics, I just can't seem to wrap my head around this one...

    Alan...
     
  18. Chris15

    Chris15 CBMod CB Mods Premium Member

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    Given that you're telling us that the switch box is only switches and the power supplies to drive the relay banks are external, you need a dry (voltage free) contact as the output from DMX. Basically this will be the output of a relay. Any other solution is going to apply a voltage as the output.

    You might be able to set the system up so that your new controller is not relay based, but rather uses electronics to connect the grounds on the installed relays. Were the supply voltage on both relay banks the same, you could consider controlling the +ve...

    I think that going relay based will give you the most likely chance of success without need to reconfigure everything.

    If you were to use Nick's board, you'd be probably needing a drive transistor arrangement per channel.
    However, if you pick your relays carefully, something like this will only draw about 11mA at 12v and so could be directly controlled...

    So yes we are kinda all on the same page without knowing it, basically the contacts of the relays we are talking about replace Switch A... (Of the schematic that wasn't included)
     
  19. epimetheus

    epimetheus Well-Known Member

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    I understand what you're looking to do here. You want to replace 'Switch A' with a DMX controlled relay, correct? If the relay control voltage is 12VDC, then the Celestial Audio board I linked earlier in this thread will work, assuming you operate the channels only at 0 or full. The Celestial Audio board is designed for dimming LED clusters. It creates pulse width modulation that allows you to dim LED's. A simpler solution here would be the Blue Point Eng. or MA Demux boards, as they are just relay output, no dimming capability. Details vary, but generally the relays are de-energized for DMX values 0-127 and energized for DMX values 128-255. Depending on the particular settings, the relay can be set to be energixed for any DMX value greater than 0.

    None of the solutions I've suggested require anything more than the controller board itself. The biggest variable I see here is the relay coil voltage. You say the low voltage source is provided by a transformers at the relay banks. Is there a rectifier and ripple capacitors between the transformer and the relays? If there is then you low voltage source is DC. If there isn't then it's AC. The direction I going with this is if the coil voltage is DC, you can use a simple single transistor switch to control the relay (the Celestial Audio board) and you only need one control board. If the coil voltage is AC, you need a relay or SCR/triac for a switch and you need multiple boards to cover all 18 of your channels. (I haven't seen any DMX relay boards that have more than 8 channels.)
     
  20. wah0808

    wah0808 Member

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    Chris15, I think you win the prize... :grin: So if I decided to use one of the devices mentioned above (because for the most part they're cheap) and 18 relays (I think I though of this in an earlier post) then I could build the interface I want... Correct?!?

    I'm just surprised that no one has had this situation before and / or has come up with a single board solution... Oh well...

    Alan...
     

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