ace Posted May 5, 2012 Share Posted May 5, 2012 Hey Guys, Probably a silly question, and I know there have been many discussions about this in the past, but is it safe to dim par36 pinspots? It is something I have always done when used in theatres without even thinking about, but I have recently noticed there are many forum posts on the interweb saying that it shouldn't be done, as dimmers as a general rule don't like inductive loads. I have a small charity event next week were I am using a very cheap dimmer (chauvet DMX-4 led) which is the best I can find to borrow for free. Because of the cheaper build quality compared to dimmers I have used in the past am I likely to have problems using it to dim pinspots? Also which is likely to be damaged the fixtures or the dimmer? It is possible to switch the dimmer to relay mode, but would prefer to fade the pinspots up if it is safe and reliable to do so! Many thanks, Chris Link to comment Share on other sites More sharing options...
pritch Posted May 5, 2012 Share Posted May 5, 2012 The simple answer is to suck it and see; it's not unsafe, but you may end up with weirdness, depending on the dimmer. I've seen it in the past where unusual loads have caused the channel to stick on. Unless the dimmer pack actually does have relays in (which I doubt), then relay mode is going to be a dimmed channel anyway, albeit one that's limited to just 0% and 100% If it behaves strangely, you'll have to go for the tried and trusted technique of putting a load lamp in parallel with the pinspot. Link to comment Share on other sites More sharing options...
ace Posted May 5, 2012 Author Share Posted May 5, 2012 The simple answer is to suck it and see; it's not unsafe, but you may end up with weirdness, depending on the dimmer. I've seen it in the past where unusual loads have caused the channel to stick on. Unless the dimmer pack actually does have relays in (which I doubt), then relay mode is going to be a dimmed channel anyway, albeit one that's limited to just 0% and 100% If it behaves strangely, you'll have to go for the tried and trusted technique of putting a load lamp in parallel with the pinspot. Ok! Well I have tried the dimmer and the pinspots and they seem to work fine. There are definitely no relays in there, as you say each channel is a dimmed channel anyway. I did wonder if it does do anything more clever in the electronics, when you change it from dimmed, to switched mode but I am guessing not! Particularily as the manual states clearly that the dimmed mode should never be used as a switch even if you are only outputting 0 or 255 from the desk, but I guess this is just to avoid people accidentally fading the channel. If this is correct I am assuming that the 3 second fade up at the start of the night is the only time the electronics are under any extra strain, and so not going to cause any long term damage... Many thanks, Chris Link to comment Share on other sites More sharing options...
paulears Posted May 5, 2012 Share Posted May 5, 2012 The problem with transformers is that they don't like waveforms that are not sine shaped - that's all. Some even make loud noises! The dimmers don't really find it extra strain, it's just that some designs behave strangely with unusual loads - and they weren't really designed with transformers in mind. However - many are fine. If they misbehave, add the load lamp. If they work - don't worry. My ancient Strands are very happy driving our low voltage star portals via big transformers. The transformers just making odd noises when used on half - a sort of rattly hum! I have blown one transformer over the years by leaving it on half for two days - and it got hot and died. The fade up of a few seconds really isn't worth worrying about. It is fair to say cheap dimmer designs may work a bit more oddly than more expensive ones. Lots of people discover the real problem isn't the transformer, just the very low power consumption, and the dimmer refuses to come on. The load lamp cures this one. I'd guess the pinspots will work fine - and you don't need to worry at all. Just try them and see? Link to comment Share on other sites More sharing options...
ace Posted May 5, 2012 Author Share Posted May 5, 2012 Thanks Paul! I think that has set my mind at ease! It is always tricky when you are trying to help someone out and have the bare minimum of equipment as there is no budget, the thought "burning out" the only dimmer before the event does make me ask the question! Cheers guys! Chris Link to comment Share on other sites More sharing options...
paulears Posted May 5, 2012 Share Posted May 5, 2012 In the worst case scenario - the transformer in the PAR fitting could overheat. The dimmer wouldn't care too much if it went up in flames, it will try to drive it if it can, and if the fault caused a short, the dimmer protection would work in the same way it would if a lamp shorted on failure. Link to comment Share on other sites More sharing options...
themadhippy Posted May 5, 2012 Share Posted May 5, 2012 The only other problem with single 36's is some dimmers dont like the low load,again a load lamp will work its magic here Link to comment Share on other sites More sharing options...
alistermorton Posted May 5, 2012 Share Posted May 5, 2012 Hey Guys, Probably a silly question, and I know there have been many discussions about this in the past, but is it safe to dim par36 pinspots? It is something I have always done when used in theatres without even thinking about, but I have recently noticed there are many forum posts on the interweb saying that it shouldn't be done, as dimmers as a general rule don't like inductive loads. I have a small charity event next week were I am using a very cheap dimmer (chauvet DMX-4 led) which is the best I can find to borrow for free. Because of the cheaper build quality compared to dimmers I have used in the past am I likely to have problems using it to dim pinspots? Also which is likely to be damaged the fixtures or the dimmer? It is possible to switch the dimmer to relay mode, but would prefer to fade the pinspots up if it is safe and reliable to do so! Many thanks, Chris FWIR ... If they're real transforners, you'll probably be fine so long as the dimmer is rated for inductive loads and the lamp draws enough current. If it's an electronic transformer then you need to check. The "transformer" need to have a marking on it designating it as suitable for use with a dimmer, and with the particular type of dimmer you have.Typical thyristor and triac wave switching dimmers are leading edge or trailing edge - the ones which work with inductive loads are leading edge, trailing edge works better with capacitive loads. Link to comment Share on other sites More sharing options...
bigclive Posted May 5, 2012 Share Posted May 5, 2012 Some of the older dimmers had issues with inductive loads where the triac was turned on by a single trigger pulse and the back EMF could cause it to turn back off. Unfortunately the positive and negative switching characteristics of triacs are usually different and in some instances this caused the transformers to be driven half-wave which made lots of noise and popped fuses. Most modern dimmer systems use continuous gate drive, so it's not such an issue. Disco dimmers tend to be designed with inductive load capability anyway, since pin spots used to be their main load. Link to comment Share on other sites More sharing options...
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