AC voltage dimmer with Triacs

Discussion in 'The Projects Forum' started by Jstuyfzand, Apr 13, 2016.

  1. Jstuyfzand

    Thread Starter New Member

    Apr 13, 2016
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    Hello,

    I am making a ball mill, and I am using a vacuum cleaner motor for the tumbling of the can.

    The can is directly connected to the axel of the motor, and I need something to control the speed, because
    30000rpm is not going to mill anything.
    I wanted to buy a voltage regulator along the lines of this:
    http://www.ebay.com/itm/220v-AC-200...478686?hash=item541f4e4f5e:g:8QsAAOSwpDdVXc27

    But I cant wait for 30 days shipping, not only ebay, and I want to learn things myself.
    I live in the netherlands and I can buy parts from conrad.nl, they have things like triacs, diacs, capacitors and potentiometers for cheap and
    fast shipping.

    I have seen multiple triac circuits, but always low powered, I need 1500-2000watts for my vacuum cleaner motor to be on the safe side.
    I am still a newbie to electronics, so I cant modify such circuits to fit my needs, and I was wondering if anyone of you had a high powered circuit design
    lying around :)

    The component on ebay looks very easy, but I cant find the exact components anywhere.
    I think and hope turning something low power into high power is just changing some components, any help is greatly appreciated!

    (I have 230V ac)

    Thanks in advance

    Jstuyfzand
     
  2. Marley

    Member

    Apr 4, 2016
    144
    40
    You are going to need some sort of reduction gearing or belts. Even with a triac speed control the motor still needs to be going at least 25% of full speed to get any power out of it.

    I would go on ebay and find a motor with a built-in gearbox.
     
  3. Jstuyfzand

    Thread Starter New Member

    Apr 13, 2016
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    0
    I want to make a voltage dimmer in general, also for other motors.
    I have a limited budget and I cant use a gearbox or something because that would make everything more complicated.
     
  4. SLK001

    Well-Known Member

    Nov 29, 2011
    818
    228
    We have a language problem. This is a ball mill:

    balll.png

    What do you mean by "tumbling of the can"?

    Also, what vacuum cleaner turns at 30,000 RPM?
     
  5. tcmtech

    Well-Known Member

    Nov 4, 2013
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    A small ball mill takes low RPM (60 - 100 RPM) and high torque (mass of load and radious of drum dictate torque) whereas a high speed vaccumm cleaner has almost no torque but very high RPM.

    Use the correct motor for the job is what I and others are saying becaseu thre is no electroinic circuit that can make a 30,000 RPM high speed low torque motor work at 100 or less RPM while providing high torque.
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,547
    2,371
    Actually a Universal (series) motor has high torque characteristics of most series field motors, this is why your car starter motor is a series motor, also wood routers etc.
    The reason is that when a load reduces the RPM it correspondingly increases the field current and torque.
    The problem is it operates in a run away condition and requires some kind of load to regulate the RPM.
    Using Triac control on a Universal motor that runs 20Krpm+ will result in a minimum practical rpm of around 5k, and for constant torque will require a feedback element to monitor rpm.
    Many home CNC's use a Router style motor in conjunction with a feedback controller such as SuperPID, but still 5krpm min.
    http://www.vhipe.com/product-private/SuperPID-Home.htm
    If you want high torque at low rpm, maybe look at a treadmill DC brushed motor.
    Max.
     
    Last edited: Apr 13, 2016
  7. Jstuyfzand

    Thread Starter New Member

    Apr 13, 2016
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    Wow! I did not except this much replies! Thanks!

    First of all, I just need a voltage limiting circuit, not just for the vacuum cleaner motor, lots of other projects!
    I can see that that wasnt clear.

    The ball mill, that I plan(Plans change :D) on using the vacuum cleaner motor with requires minimal torque.
    The can that will tumble (I mean slowly rotate with that @SLK001) is very small, not larger than a soup can.
    I am always on the lookout for new motors, but lets focus on the circuit, this is all about circuits, not all about ball mills :)
     
  8. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,800
    1,103
    Even if you could use a triac-based controller with a vac motor you are unlikely to get below about 10% of the max speed, i.e. 2000rpm. That is still way too high for a ball mill, but is no doubt usable for other purposes. An old windscreen-wiper motor, with its gearing, would be more suited to use with a mill.
    There are plenty of circuits online for triac-based dimmers.
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,547
    2,371
    With the item referenced in the OP, you are limited in motor, it is no good for a AC induction motor or a DC motor, about the only AC motor commonly available is the Universal motor.
    I would look for an ex treadmill DC brushed P.M. motor.
    You can get the PWM controllers like the triac you ref. or build one is fairly simple.
    Max.
     
  10. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That would be one exception to control with Triac as it is shaded pole motor.
    The only thing it is 110vac.
    Max.
     
  12. Jstuyfzand

    Thread Starter New Member

    Apr 13, 2016
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    I understand that the vacuum cleaner wont do, but could we focus on the circuit? :S

    And one thing with normal motors is that their axl is smooth, I need something that I can put a bolt on or something.
    Im going to the scrapyard soon.

    But anyway, how do I transform a triac circuit for low wattage into a high powered one?
     
  13. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    At about 5 bucks it would be a perfect slow rotating motor for his miniature ball mill (soup can full of ball bearings).
    Let him learn about triac dimming on a project for which it appropriate.
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Use a triac in the circuit that is rated for your expected load, there should be little or no change to any other component for the range you want.
    Max.
     
  15. Jstuyfzand

    Thread Starter New Member

    Apr 13, 2016
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    Thank you, I was worried about that the Capacitors and resistors would change as well.
     
  16. Jstuyfzand

    Thread Starter New Member

    Apr 13, 2016
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    triac-lamp-dimmer-circuit.jpg
    I was thinking about this, it seems like the most simplified circuit.
    I guess I just have to get a capacitor that has a voltage above the activation voltage of the diac?
    En then just get a high powered triac.

    Is this circuit appropiate for inductive loads? If not, what changes should be made?
     
  17. MaxHeadRoom

    Expert

    Jul 18, 2013
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    For inductive loads RC snubbers are often included.
    Max.
     
  18. tcmtech

    Well-Known Member

    Nov 4, 2013
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    Well this is about the simplest phase angle firing control circuit I know of that has a full phase angle (0 - 180 degrees per half wave) range and stable control plus can work well with inductive loads with minimal changes or additional components other than a optocoupler and a properly sized Triac OR dual SCR type power circuit.

    Basically, all you need to do to make it scalable on voltage and power is to omit the lamp and replace the SCR on the right side with an optocoupler that fires a much larger Triac or SCR set on the AC power side of whatever you are trying to control.

    ujt-trigger.jpg
     
  19. Jstuyfzand

    Thread Starter New Member

    Apr 13, 2016
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    I need to let that circuit sink in for a while, Im still very new at this.

    I heard about Triacs having built in inductive load protection, would that still require altering a circuit for inductive loads?
     
  20. tcmtech

    Well-Known Member

    Nov 4, 2013
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    Let it soak in and do some reading on phase angle power control of inductive loads and ten tell us what you think after that. :eek:

    BTW when sizing a thyristor-based control system for inductive loads consider the basic rule of sizing the devices at a minimum of 2X the peak voltage and 4X the anticipated amps.

    The rest you have to figure out. ;)
     
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