gareth Posted January 24, 2009 Share Posted January 24, 2009 Got a production coming up which requires many (20+) circuits of 12v lamps - birdies and so on - substage. Doing it the 'traditional' way would tie up a lot of dimmers, and because of the way our space works would involve the running of an awful lot of cable. So I got to wondering ... is there such a thing as a low-voltage dimmer pack? By which I mean, something which will take a hard mains input and a DMX signal, and spit out multiple dimmed 12v outputs for feeding MR16s and so on? I don't remember ever having seen such a beastie, but that's not to say that it doesn't exist. Anyone ever seen anything like this? Link to comment Share on other sites More sharing options...
dbuckley Posted January 25, 2009 Share Posted January 25, 2009 The old NJD four channel install dimmers (the one I have is non-DMX) describe how to do this in their instructions, but you need to supply the 12V AC yourself. Pretty much any simple dimmer (like a Betapack) could be modified the same way, but installation dimmers are "better" as they dont have 15A sockets all over them... Link to comment Share on other sites More sharing options...
danjshelton Posted January 25, 2009 Share Posted January 25, 2009 Hi Gareth, The option that I've thought of isn't really the perfect answer, but thought it deserved a post as may solve other people's low voltage problems? There is a product from Avolites (Which you may be aware of) that is a 4 channel 12v dimmer, unfortunatly it is designed to be powered from batteries (12, 24, 36 or 48 volts) and has wireless DMX built into it, so a bit overspec for what you require, although it may be worth a call to avo to see if there is a way that this can run from mains? I doubt it though as it runs off DC on the input side. Anyway the link is here for the Art DC Dimmer. Cheers Dan Link to comment Share on other sites More sharing options...
Ben Posted January 25, 2009 Share Posted January 25, 2009 Hey The Light Processor Paradims can have a low voltage PCB fitted so they will do exactly what you need. Ben Link to comment Share on other sites More sharing options...
Tomo Posted January 25, 2009 Share Posted January 25, 2009 City Theatrical also have a 3-channel extra-low-voltage dimmer "ShowDMX 5620" (Direct link to PDF) I've had a chance to play with one and it's quite cute, and very tiny to boot. Like the Avolites dimmer, it does need an external 12VDC power supply. Link to comment Share on other sites More sharing options...
musht Posted January 26, 2009 Share Posted January 26, 2009 Slight catch with triac dimmers and 12V A.C. is 1.4V drop across triac, very visible with 12V lamps. Current is till quite high 4A for a 50W lamp so they also run hot. LV I/O on some dimmers better used at 24V for things like stair nosing, V drop not so noticeable and underunning extends lamp life. Things like ART use bipolar outputs, can get very low on resistance, and DC PWM. High density low power dimmers and electronic trafos near the lites 25 * 220W 230V channels http://www.theater-technisch-lab.nl/framflat.htm Link to comment Share on other sites More sharing options...
Andrey Posted January 26, 2009 Share Posted January 26, 2009 Hi, Gareth.I never tried but think it is possible to use DMX dimmable power supply units for LED’s. For example from Ledelec solutions provided by Electron, such as CDS.055( 9 x 80W channels per 2 units rack mounted device). Link to comment Share on other sites More sharing options...
slipstream Posted January 26, 2009 Share Posted January 26, 2009 I know I will get shot down in flames but if you are running no load whatsoever (for a dimmer) why not put a beta or similar rack local to all the 12v stuff and supply the mains feed with a single line- if the 12v load will all run from a 13A / 15A supply, you save the cable run and and ETC 12 way can be found much easier than a specialist 12v unit Sam Link to comment Share on other sites More sharing options...
gareth Posted January 26, 2009 Author Share Posted January 26, 2009 We have a quantity of 18-way touring racks (three Act6+ in each) which would do the job at a push - but something much lighter (easily tourable) and much smaller (will fit underneath the rake) would be infinitely preferable. Link to comment Share on other sites More sharing options...
Ynot Posted January 26, 2009 Share Posted January 26, 2009 May be a simplistic answer, but what about a handful of those 4-ch Showtec type IEC outlet dimmers? As the load is all low current, you'd likely get by with just daisy chaining a single mains feed to all you need... Link to comment Share on other sites More sharing options...
neilalexrose Posted January 26, 2009 Share Posted January 26, 2009 Along the same lines as the Avolites product, this offering from theatrewireless.com. RC4 wireless dimmer It's a 4 channel low voltage dimmer, again you do have to feed it between 6v-30vdc, but it seems like quite a nifty little product. Received one of the two dimmer options, which I have to install into an oil lamp, so we can have a flickering practical controlled from the Lx Desk. The unit itself is just a bit bigger than a matchbox. Very cute! May be barking up the wrong tree for what you exactly want, probably alot more expensive than a showtec dimmer, but the product seems pretty nifty to me, and cheaper than some of the other wireless DMX options on the market at the moment. Link to comment Share on other sites More sharing options...
musht Posted January 27, 2009 Share Posted January 27, 2009 May be a simplistic answer, but what about a handful of those 4-ch Showtec type IEC outlet dimmers? As the load is all low current, you'd likely get by with just daisy chaining a single mains feed to all you need... Multidims work well with LV trafos, both wound and electronic, depending how long run is, purchase possibly cost comparitive with hire rate for a big rack. Link to comment Share on other sites More sharing options...
dbuckley Posted April 18, 2009 Share Posted April 18, 2009 *Bump* I suddenly find myself with the requirement for a bunch of 12V channels, so I've repurposed an earlier dimmer design, and I now have 16 PIC outputs needed to be connected to a controlling device. Given the loads are incandescent lamps they dont care much if its AC or DC, so my control device choices are triacs, thyristors, or something like power darlingtons. In my old age I seem to have become somewhat indecisive, so I would appreciate some advice, with (I think) the parameter needing optimisation being voltage drop acreoss the controlling device, and the limitations of the phase control signal, which is about 6.25mA at 5V, ie one pin of a PIC. (yes, PICs can source more current per pin, but for this design the sixteen phase shift outputs are on ports C and D of a PIC17C44, and the spec sheet gives the maximum combined source current of ports C,D and E as 100mA) Link to comment Share on other sites More sharing options...
jonathanhill Posted April 18, 2009 Share Posted April 18, 2009 So I got to wondering ... is there such a thing as a low-voltage dimmer pack? By which I mean, something which will take a hard mains input and a DMX signal, and spit out multiple dimmed 12v outputs for feeding MR16s and so on? I don't remember ever having seen such a beastie, but that's not to say that it doesn't exist. Anyone ever seen anything like this? Mode Lighting do a transformer/dimmer which would be ideal. AC Lighting stock them. They take hot power and DMX and provide a dimmed 12V ouput. Dimensions are probably 12"x3"x1.5", although I can find out exactly if you need when I go into the loft later. List is around £80 for a 105VA. Link to comment Share on other sites More sharing options...
Tomo Posted April 20, 2009 Share Posted April 20, 2009 In my old age I seem to have become somewhat indecisive, so I would appreciate some advice, with (I think) the parameter needing optimisation being voltage drop acreoss the controlling device, and the limitations of the phase control signal, which is about 6.25mA at 5VMost Triacs and SCRs (thyristors) want more current than that to reliably turn on. If you can go DC, then your best bet is a logic-level N-Channel MOSFET.Insertion loss is in the <0.5 ohm range, and gate current draw is essentially zero. (They are internally capacitors) 1-Ohm resistor between PIC pin and MOSFET gate, 1 Meg-Ohm pull-off resistor. Link to comment Share on other sites More sharing options...
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