Some Old Dimmers and a DMX cable...

[Dazzler91]

Hi, were in the process of preparing for our annual school production and, unlike most years, we've prepared in advance slightly! (ok: the performance is 3 weeks away) - anyways we have more time that usual and as such have been able to repair and cobble together a sizable number of our lights; around 40-50 in total. Anyways the problem is that we only have a 24ch rig (4 betapack 2's) so it is likely that we are going to run short by a sizable amount even with pairing some together.

 

So we need to get more (probably 2) patch bays! We have around 4 older analogue dimmers however we also have a frog and therefore no way to control them. We also do not have enough cash to buy new dimmers though there's a hundred or so left over for negotiation .

 

We are therefore looking to either renting, or reusing the older bays. Renting however is coming out at around 100-150 for the time we need them for so would it be more sensible to reuse what we have it for the future?

 

From a little research I think were looking for a demux in that case? something like the BOTEX ME-72?, And was wondering A) how reliable such a rig would be once set up, (do you loose any control while fading / is there flickering or do the lights behave like our others do? I'm also wondering how to take the 25 pin analogue from the back and into the 4 old dimmers (they have small circular (kinda midi-ish?) connections - helpfully labeled 'control'. Is this something we would have to solder together ourselves or can you buy an off-the-shelf adapter?

 

I was also looking at the Millford Instruments kits, are these better value or just more trouble than there worth!

 

any recommendations welcome, and thanks in advance,

[mutley]

Hi Dazzler91

 

I have a similar problem with our upcoming production: 4x 6ch dimmers, 3/4 channels dead, massive lighting plan!

 

What I did was buy some old dimmers off ebay £31 for two, plus £5 carriage on each! Since then I've spent some money on repairing them (capacitors explode inside!), servicing them, and upgrading them to have a Socapex output as well as the front sockets. We already have a demux, so I just made another 25 pin D plug (like a printer connector) to 4x 8pin DIN plugs.

 

Unfortunately, your show coincides with ours so I won't be able to lend/hire any of it out!

 

But if you know any friendly electronic technicians who would be prepared to help you, buying an old dimmer and reviving it can often be the chepest way. Plus, you don't have to give it back afterwards!

 

Also, try asking your local community centres, Am-Dram groups, etc, and you may be able to do a deal with them...

[themadhippy]

something like the BOTEX ME-72?, And was wondering A) how reliable such a rig would be once set up, (do you loose any control while fading / is there flickering or do the lights behave like our others do? I'm also wondering how to take the 25 pin analogue from the back and into the 4 old dimmer

Ive used both a botex and a showtec model,which looks and operates exatley the same as the botex, .without any problems The only slight problem is the demux sends all the outputs to full on very briefly when you first turn it on,so you got to remember to turn it on first,then the dimmers.,As for the control cable yes you can buy pre made leads,or buy a fully wired 25 pin d sub lead cut 1 end off and add suitable connectors for your dimmers.

[Dazzler91]

hi mutley, that sound like a great plan for you, but for us we have the dimmers but not the demux! -out of interest what demux are you using and how much was it? I think a demux is going to be the best bet and that way we also get ourselves a extra 24ch portable rig which could be useful on its own. Its just a matter of finding a cheap but reliable demux.

 

The only slight problem is the demux sends all the outputs to full on very briefly when you first turn it on,so you got to remember to turn it on first,then the dimmers.

 

Thanks!

[mark_s]

A more creative solution would be to play around and see what you can/can't pair, what you might be able to get rid of if push comes to shove, and then see how much you're short and make it up with the odd Alphapack and/or creative repatching. Part of the skill of lighting something is being able to work within the limits the space presents you.

 

If you decide to completely ignore that advice however, check how much power you have available before you start buying more dimmers. It'd be a bit silly to buy some new toys and discover they can't be used anyway as you can't power them (you may have already done all of this, but as your post doesn't mention it I thought I should point it out just in case)

[Dazzler91]

A more creative solution would be to play around and see what you can/can't pair, what you might be able to get rid of if push comes to shove, and then see how much you're short and make it up with the odd Alphapack and/or creative repatching.

 

Thanks for the advice Mark and I take your point, but for the moment at least I am going to completely ignore that advice :unsure: at least until I have found how (in)feasible getting our old dimmers working is going to be.

 

I'v also done a little more research on the dimmers...

There Strand Tempus 6 x 10A 5A portable Dimmers Using 8-pin Bleecon (locking DIN connector)

 

Is there a premade adapter that will take the 25 pin serial cable to 4x bleecon? and does anyone know what the deal with the polarity is?! - I know some are 0v to 10v and others 0v to -10v input.

 

Im also a little aware of the power drain adding these to the rig will be, there each currently wired to 13a mains plug, is this safe/desirable for a 6ch dimmer nowadays providing they are connected safely? If they are run off 13a I wouldn't have to worry about 3 phase at all would I? (sorry im not a technician and have little concept of 3 phase implementation) Additionally all our lights are 15a not 5a, does this matter? would we be overloading them plugging in 15a lights?

 

Thanks for everyone's help,

[boatman]

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I'v also done a little more research on the dimmers...

There Strand Tempus 6 x 10A 5A portable Dimmers Using 8-pin Bleecon (locking DIN connector)

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Have a look at the Strand Archive for more information on this dimmer pack.

 

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Is there a premade adapter that will take the 25 pin serial cable to 4x bleecon? and does anyone know what the deal with the polarity is?! - I know some are 0v to 10v and others 0v to -10v input.

 

Use the "Search the Blue Room" function at the top of the page to find references to "Botex ME-72". There's lots of them.

 

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Im also a little aware of the power drain adding these to the rig will be, there each currently wired to 13a mains plug, is this safe/desirable for a 6ch dimmer nowadays providing they are connected safely? If they are run off 13a I wouldn't have to worry about 3 phase at all would I? (sorry im not a technician and have little concept of 3 phase implementation) Additionally all our lights are 15a not 5a, does this matter? would we be overloading them plugging in 15a lights?

 

Thanks for everyone's help,

 

Search for references to running dimmer packs from 13A ring mains.

[themadhippy]

The tempus are like most older strand gear -10v the botex demux will happily do this..The power issues gets a bit more complicate /c ontroversial and your best geting a sparks in.Me personally would be tempted to put 2 dimmers per existing supply your still limited to a max load of 12kw, per supply but spread over 12 channels not 6 giving you a bit more flexibility to the rig,If you go down the 13A route you'll be limited to about 3kw or 6 500w lamp per pack ,but dont forget to check what else is on the 13A socket circuit

[tom_the_LD]

Im also a little aware of the power drain adding these to the rig will be, there each currently wired to 13a mains plug, is this safe/desirable for a 6ch dimmer nowadays providing they are connected safely? If they are run off 13a I wouldn't have to worry about 3 phase at all would I? (sorry im not a technician and have little concept of 3 phase implementation) Additionally all our lights are 15a not 5a, does this matter? would we be overloading them plugging in 15a lights?

 

Thanks for everyone's help,

Just because the lights have 15A plugs on them, it does not mean the light is 15A. It just means the plug is rated to having 15A drawn through it. Do you know all about Ohms Law and Joules Law and the such?

 

Lets take a PAT 64 with a 1000W lamp running at 240v.

 

1000/240 = very roughly 4.16A. Therefore it is fine to have a 15A plug on it. This also means you can safely run two of these off one channel on the tempus dimmer rack, as each channel is fused to 10A and when added together there is just over 8A of PAR 64.

 

HOWEVER - As each one of these dimmer packs has a 13A plug on the end, it also means that you can't draw more than the plug will allow. Say you are running at 240V.

 

13 * 240 = 3120 so you can only draw 3120W from each dimmer pack in the perfect world. But there is more - if you run all these dimmers on the same ring main, then you could trip the RCD. If the RCD is rated at 32A, it means IN TOTAL across all 4 of the dimmer packs, you can't draw more than 7680W - again working on 240V. This would be two of the dimmer packs running at full with another running just one PAR 64.

 

So if you do decide to run these extra 4 dimmers, then you need to find out stuff like which ring main is which, what the RCD's are rated to etc. Also you shouldn't run LX on the same ring main as sound - so I've always been told!

 

 

You also say you want to rent in another patch bay. I'm not entirely sure what you mean here because the patch bay you have is how many circuits you have end of story. Adding another patch bay wouldn't suddenly increase the amount of circuits you have in the rig. It might be worth looking into hiring some socapex.

 

 

Hope at least some of that makes sense! And if anyone spots a flaw in my electrical formulae, please let me know so I can rectify it!

[mark_s]

I second the suggestion to get a spark in. Assuming said dimmers are being supplied from a ring main, assuming you happen to have everything up at once, that limits you to 300W per lantern ((30x240) / 24). Assuming the majority of your lanterns are something more sensible than 300W - let's say 650W fresnels for now - that means you can (theoretically) have approximately 11 lanterns up at full at once ((30x240) / 650). Adding more dimmers powered from the same circuit won't increase that number as the total available power is the limiting factor here, and not the number of dimmers. Also the numbers are 'best-case' - if other things are plugged in and switched on somewhere else but on the same circuit, the numbers go down.

 

Like themadhippy said, you really need to get an electrician in to have a look for you.

[tokm]

Hope at least some of that makes sense! And if anyone spots a flaw in my electrical formulae, please let me know so I can rectify it!

Looks fine.. apart from the fact RCD's don't trip when you attempt to pull to much current through them :) MCBs or RCBO's deal with over current protection.

 

Moving on...

 

In regards to dsub breakout's. If your not feeling particularly confidant making one yourself, give Paul @ 10 out of 10 a call/email. He sells them, as shown here.

 

HTH,

 

T

[mark_s]

It would be (reasonably) safe to say that according to Tom's and Marks calculations we could run 2 dimmer's off one of the sockets and be able to use 5 of the 6 channels on each of the dimmers to run single 500w lamps?

 

Definitely not. 13A = ~3000W. You could have six 500W floods up at any one time, as 3000/500=6. The way to work it out is with P=IV, where P is power (in watts), I is current (in amps) and V is potential difference ('voltage') in volts. V is constant and theoretically 230, although it may be reasonably safe to assume it's 240. Therefore you end up with I=P/230 and P=I*230. Use those to calculate power requirements, and what can and can't be run off what.