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Thread: Lumia Motor Speed Controller Wanted

  1. #21
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    Quick PWM primer:

    You need your PWM controller to be rated for the input voltage you're going to feed it, or higher. You can use a module rated 24V on a 12V motor without hurting the PWM module, so long as the specs don't list a minimum voltage. You have a 12V motor, so I imagine you'll use a common 12V power supply. Your PWM module cannot be rated any lower than that.

    PWM modules control speed by turning the power to the motor on and off very quickly, usually somewhere between 8kHz-20kHz depending on motor size and power. I have a treadmill controller whose PWM rate is ten hertz (yes, ten!) but yours should be above 16kHz to avoid an audible whine. There can be some interaction between the inductance of the motor coils and the drive frequency that affects power transfer and noise level. When the PWM signal is ON, the full voltage is applied, so you get all of your torque, but it's not applied for very long, so you don't get up to speed. The width of the pulse (on time vs. off time) controls how much speed the motor can build up. Because the pulse rate is very fast, it smooths out to a stable speed. If you set the speed with no load on the motor, and then load it down, the speed will change, but with PWM you can adjust things so that you have slow speed AND lots of torque.

  2. #22
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    Jem,I've gutted simple dmx lights for an easier way round of controlling mirrors plus you have dmx control over speed,rotation direction and in some you have 'shake' features (martin destroyers) where the motor will bounce as well as rotate.Plus all the mounts are ready made,It's just a case of motor assembly and dmx board,remove the reflector/gobo wheel and mount your mirror/grating.Control via a cheap dmx controller,the good thing about using dmx is you can add to it and still have independent control of each motor.
    Hope this can get you thinking in an easier direction
    lighting the way since 89

  3. #23
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    ^^^ Great explaination Tribble, many thanks

    Steve (Laserhobbit) has kindly offered to pop by tomorrow, so i'll have a better idea as to how good these will work after his visit.

    @Clearblu... Yes, Dave at Lasershowparts sent me a PM a short while ago explaining a little about controlling by DMX. In actual fact I purchsed a DMX controller from him a while ago for this project but didn't realise i'd be able to use it to control motor speed etc. I think I need to do some reading about his analogue control board... Thanks for your input though, i'll get this cracked one day

    Cheers

    Jem
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001

  4. #24
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    Hi Jem

    I thought I'd wake up this old thread as I'm in a similar situation now to the one you were in. Did you have any luck finding an easy solution in the UK?

    I have just bought a Futaba S3003 servo for £7 and an Etronix 3 mode servo tester for £2.99 before reading this thread and plan to mod it so that it turns 360 deg and see how slow it can turn with a lumia wheel attached directly. If it isn't slow enough or is too jerky, I am hoping it has the torque to drive some pulleys.

    I also ordered a similar synchronous motor to the one you have pictured above but as noted, building an inverter to change frequency is a pita (plus I've lost most of my electronics knowledge over the years).

    Keith

  5. #25
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    I've pretty much come to the conclusion that smooth movement overules everything else where lumia is concerned.

    I've tried supplying lower than rated voltage to motors (they stall & have no torque), i've tried PWM controllers (either noisy or jerky) and in the end i've decided that gearing or pulleys is the way to go. Get a nice smooth slow motor ~1RPM or less and slap a series of pulleys on it with a final drive to the lumia wheel(s).

    This is the route i'm now taking as i've pretty much tried all other alternatives and haven't been really satisfied with the results.
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001

  6. #26
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    Cheers Jem. Yes, the smoothest and slowest I've seen so far are Swamidog's wheels which are belt driven. I was trying to avoid that as I don't have a workshop or many suitable tools - but where there's a will and all that.

  7. #27
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    Keith,

    Servos and lumia were discussed several years back on PL. Even with a continuous rotation servo and a low-speed mod, it was still too fast as confirmed by both Stuka and myself. While it may be more expensive than an AC synchronous motor, why not consider a DC gearmotor instead? This will give you both slow, smooth speed and direction control, without building anything mechanical or electrically complicated. Dave at lasershowparts.com has a DMX/analog control board that should be able to control a DC gearmotor either directly or with a simple circuit. The DC gearmotors can be found a www.servocity.com - these are as good, if not better than the Hankscraft motors that were popular early on.

    If speed or direction control isn't needed (or is too expensive), you can simply lower the voltage to the gearmotor if it's too fast and let it run. It's still a bit of money for these gearmotors with shipping, but servos can be used for most other rotating effects you may want.

    Greg
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  8. #28
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    I am going to be using one of these http://www.ebay.com/itm/181196313764...84.m1423.l2649 with some 0.6 RPM DC gearmotors. The PWM should be in the khz range so it should be pretty smooth. I am only going to be using the "dimming" feature and not the other channels. It is also DMX so I can activate it via software. I have posted in a few other threads about these gearmotors. I have a few of them and they are pretty quiet. http://www.ebay.com/itm/171020215599...84.m1423.l2649. I will put it this way, the fans in my projector are louder and with those running, I can't even hear these motors.
    If you're the smartest person in the room, then you're in the wrong room.

  9. #29
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    Thanks Greg. I'm in the UK and have been struggling to find DC gearbox motors with quoted RPM. They often just have ratios of the gear box which doesn't usually help.

    No Hankscraft motors on the bay without paying £26 postage

    I'm going to keep the search up!

    Keith

  10. #30
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    swamidog is online now Jr. Woodchuckington Janitor III, Esq.
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    let me know how those work out.

    Quote Originally Posted by absolom7691 View Post
    I am going to be using one of these http://www.ebay.com/itm/181196313764...84.m1423.l2649 with some 0.6 RPM DC gearmotors. The PWM should be in the khz range so it should be pretty smooth. I am only going to be using the "dimming" feature and not the other channels. It is also DMX so I can activate it via software. I have posted in a few other threads about these gearmotors. I have a few of them and they are pretty quiet. http://www.ebay.com/itm/171020215599...84.m1423.l2649. I will put it this way, the fans in my projector are louder and with those running, I can't even hear these motors.
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

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