mitchino Posted September 3, 2012 Share Posted September 3, 2012 I've borrowed a mirror ball for a wedding I'm hosting at my studio. I want to slow down and have control over the speed of rotation. Can I route it through my old Arri dimmer rack and use that to adjust the speed? Link to comment Share on other sites More sharing options...
Richard CSL Posted September 3, 2012 Share Posted September 3, 2012 no that wont work as it will be an induction motor which gets it's speed from the freq of the mains.Mirror ball motors come in a variety of speeds normally 1 or 2 rpm.May be best to ask at a local disco shop for a slower one. Link to comment Share on other sites More sharing options...
greenalien Posted September 3, 2012 Share Posted September 3, 2012 You can certainly get variable speed mirror ball motors, but they don't come cheap! http://www.astralonline.co.uk/showtec-mirrorball-motor-DMX-2-channel--50cm10kg-991-p.asp Note that this uses DMX control, so you still can't control it from a dimmer. Link to comment Share on other sites More sharing options...
Jivemaster Posted September 3, 2012 Share Posted September 3, 2012 The standard mirror ball rotator is an induction motor and usually something (motor or dimmer) will die they really don't work even on full power. Please use a real switch with contacts. the typical speeds are 0.5 - 2 RPM and bigger balls look better slower. Light Engineering (Walthamstow) did have a great range of mirror ball related stuff. Link to comment Share on other sites More sharing options...
mitchino Posted September 3, 2012 Author Share Posted September 3, 2012 I notice that earlier/further down on this forum someone had asked a similar question and was told that if they wired a lantern in parallel with the motor then it would work. Is that true? Link to comment Share on other sites More sharing options...
Jivemaster Posted September 3, 2012 Share Posted September 3, 2012 It's likely to work, but the all pervading stink of a burned out motor will be noticed by all and a blown dimmer channel will cost you money so I'd still go for a piece of wire and plug it into a switched 13a socket. For all but the biggest motors I'd be surprised if it consumed 10watts. Link to comment Share on other sites More sharing options...
timsabre Posted September 3, 2012 Share Posted September 3, 2012 I notice that earlier/further down on this forum someone had asked a similar question and was told that if they wired a lantern in parallel with the motor then it would work. Is that true? It may work for start/stop, but you will not be able to control the speed as you originally wanted. And there is a high chance of damaging the motor. Link to comment Share on other sites More sharing options...
mitchino Posted September 3, 2012 Author Share Posted September 3, 2012 Ok, thanks guys for all the info, switched it is. Link to comment Share on other sites More sharing options...
bigclive Posted September 4, 2012 Share Posted September 4, 2012 The synchronous motors in most mirror ball rotators are fixed speed. Their power rating is normally in the 2 or 3 watts area and if you did put a parallel load to try and dim the speed down then it would run at full speed down to a random level and then jitter about with a net speed of approximately zero. Most small rotators go far too fast these days, but if you go for the mirrorball rotators designed for much larger and heavier balls (same motor more gears) then the slower rotation looks much better. Link to comment Share on other sites More sharing options...
dbuckley Posted September 4, 2012 Share Posted September 4, 2012 The synchronous motors in most mirror ball rotators Indeedy, synchronous. Not induction as a few folks have suggested. Of course, syncronous motors are locked to the input frequency, so if you could find mains at 35Hz it'd go slower... Link to comment Share on other sites More sharing options...
greenalien Posted September 4, 2012 Share Posted September 4, 2012 syncronous motors are locked to the input frequency, so if you could find mains at 35Hz it'd go slower... so it should be possible to use a PWM motor speed controller, such as those used in some mains power drills, for example, to vary the speed? Also, even if you don't change the speed, if you stop the motor and wait a second or two for the ball to stop spinning and just start to move in the opposite direction, reapplying the power at that time will result in the ball spinning in the opposite direction. This is more effective with a pair of mirror balls, where having them spin in opposite directions can look good. Link to comment Share on other sites More sharing options...
timsabre Posted September 4, 2012 Share Posted September 4, 2012 so it should be possible to use a motor speed controller, such as those used in mains power drills, for example, to vary the speed? No, drill motors are not synchronous motors. Mains drill speed controllers do not vary the mains frequency (which would be rather difficult), they PWM the mains to vary the power into the motor - basically just a dimmer. Link to comment Share on other sites More sharing options...
bigclive Posted September 4, 2012 Share Posted September 4, 2012 I think the mains drills use phase angle control as opposed to the PWM used in the cordless drills. Neither is suited to changing the speed of a synchronous motor. The hint at using a variable frequency motor drive is viable, but cheap synchronous motors are simple devices (most don't even have a fixed direction as mentioned above) and may require their inertia and mass to provide locked rotation. Now on the other hand... If you found a stepper motor capable of taking a vertically suspended load from its shaft, then you could have any speed you liked, with the chain and mirrorball inertia removing the stepping from the direct drive motor output. In the past small DC motors have been used like this for slow rotation of objects in alternate directions by simply pulsing the motor briefly so it "winds up" the cord to the load and letting inertia and torsion smooth the flow. For those with the knowledge, this technique can be used to make a small BEAM controlled solar mirrorball for your window. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.