alibongo Posted February 28, 2009 Share Posted February 28, 2009 Hi there, I need to turn some little battery powered lights into something I can run off a dimmer, any advice on how to do this please? I'm gonna assume transformers will be involved! Cheers. Link to comment Share on other sites More sharing options...
tom_the_LD Posted February 28, 2009 Share Posted February 28, 2009 A little bit more information would be helpful. Like what the units are, how many you plan on doing and it may well be worth sticking the dimmer you're going to be using up here too. Link to comment Share on other sites More sharing options...
alibongo Posted February 28, 2009 Author Share Posted February 28, 2009 They're dolls with light up wings. Totally normal thing to run off a dimmer...... Not got them yet just waiting for them in the mail, I'll post again when I have more details then. Thanks! Link to comment Share on other sites More sharing options...
smalljoshua Posted February 28, 2009 Share Posted February 28, 2009 Just get a dim-able transformer with the right voltage and wattage. Josh Link to comment Share on other sites More sharing options...
Davethsparky Posted February 28, 2009 Share Posted February 28, 2009 Just get a dim-able transformer with the right voltage and wattage. Josh Not necessarily. The lights are currently run from a battery so are getting a DC supply, Without more information we can't possibly say whether or not they are capable of working on the chopped-up AC that comes out of a dimmer. If the light source is LED or if there is any electronics at all in the unit then feeding them with AC could cause damage. Link to comment Share on other sites More sharing options...
smalljoshua Posted February 28, 2009 Share Posted February 28, 2009 It is possible to get dim-able DC output transformers. I would have thought if the OP was confident enough to be able to change a Practical from battery operation to mains power he would be able to choose the correct type of transformer. Josh Link to comment Share on other sites More sharing options...
Johnno Posted February 28, 2009 Share Posted February 28, 2009 It is possible to get dim-able DC output transformers...Josh Dim-able transformers are designed to run off the exquisitely perfect sinusoidal waveform that issues forth from the National Grid and might not enjoy a chopped-up input from an electronic dimmer... which itself might not like having an inductive load sitting across its output terminals. Suck it and see? Link to comment Share on other sites More sharing options...
Davethsparky Posted February 28, 2009 Share Posted February 28, 2009 I would have thought if the OP was confident enough to be able to change a Practical from battery operation to mains power he would be able to choose the correct type of transformer. If that is the case then why is he here asking for advice on the best way to do this? I was merely trying to point out that it may not be as simple as just plugging a transformer into it. Although it seems obvious to us, the OP may not realise that the output from the dimmer is nothing like a sine wave as would be expected from a normal hard-power mains supply. Link to comment Share on other sites More sharing options...
themadhippy Posted February 28, 2009 Share Posted February 28, 2009 Erm LED's will quite happily run on A.C. Link to comment Share on other sites More sharing options...
GridGirl Posted February 28, 2009 Share Posted February 28, 2009 Surely it's no different to running par16s (of the 12-volt variety, not the 240-volt variety!) off a dimmer, via a dimmable transformer?! We do this all the time; it's a rare day that the par16s get run off a battery (although I have just finished a show which did do that!). You may find that the lights are under the minimum load which the dimmer needs to work properly (it varies from dimmer to dimmer) but that's easily solved by pairing a spare lantern (hidden somewhere out of sight) with it to create a dummy load - otherwise you may find the lights don't dim all the way down to nothing, they'll glow slightly. Link to comment Share on other sites More sharing options...
Davethsparky Posted February 28, 2009 Share Posted February 28, 2009 Erm LED's will quite happily run on A.C. Really? I was under the impression that they had to be in inverse parallel on an AC supply or else the reverse voltage would be too much for them. Although I admit I have never really thought about it so am happy to stand corrected if they can be run on AC (with the appropriate current limiting of course) Link to comment Share on other sites More sharing options...
jonathanhill Posted March 1, 2009 Share Posted March 1, 2009 Dim-able transformers are designed to run off the exquisitely perfect sinusoidal waveform that issues forth from the National Grid and might not enjoy a chopped-up input from an electronic dimmer... which itself might not like having an inductive load sitting across its output terminals. Suck it and see? Erm no they are not. They are designed to be fed from a triac type dimmer. Otherwise how will they dim? Where has the inductive load come from? Slightly OT, but Mode Lighting do a DMX dimmable transformer that takes 240V and data in and outputs 0-12V. At around £80 a unit, they are not a bad price, but also can be located locally to the output device, thus cutting down the LV supply leads. Link to comment Share on other sites More sharing options...
boatman Posted March 1, 2009 Share Posted March 1, 2009 The DMX - LED9 driver board from Milford Instruments sounds like the ideal candidate for this task. Link to comment Share on other sites More sharing options...
Davethsparky Posted March 1, 2009 Share Posted March 1, 2009 Dim-able transformers are designed to run off the exquisitely perfect sinusoidal waveform that issues forth from the National Grid and might not enjoy a chopped-up input from an electronic dimmer... which itself might not like having an inductive load sitting across its output terminals. Suck it and see? Erm no they are not. They are designed to be fed from a triac type dimmer. Otherwise how will they dim? Where has the inductive load come from? A basic transformer is made of two coils around a core, A coil is an inductor therfore is seen by the dimmer as an inductive load. Johnno was replying to the post about DC output transformers which may very well not appreciate having impure AC input. The DMX - LED9 driver board from Milford Instruments sounds like the ideal candidate for this task. Only if the lights in question turn out to be LEDS and if DMX is available with enough spare channels. Link to comment Share on other sites More sharing options...
KevinE Posted March 1, 2009 Share Posted March 1, 2009 Erm LED's will quite happily run on A.C. No they wont. The need a parallel inverse diode to prevent back-driving and then the correct dropper resistor. High current high brightness LEDs usually have a constant current controller pcb for professional use. Link to comment Share on other sites More sharing options...
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