Linear Motor driver Circuit

Discussion in 'The Projects Forum' started by zohonie, Dec 2, 2010.

  1. zohonie

    Thread Starter New Member

    Dec 2, 2010
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    Hi All,

    I'm trying to building a device that would move back and forth with controllable frequency and magnitude. I'm would like to use either a servo or a linear actuator to do this (Firgelli Automations have decent onces). The linear actuators that I looked at so far would move forward if a postive voltage is applied and backward with change in polarity. Since I would like to make my device work for days, I would like to either purchase a circuit or an IC to do the change of polarity for me. I came across a circuit called a H brdige that would do that, but at this point I'm not sure how I can modulate how often the circuit would change polarity. If you know where I can buy such a circuit or if you would like to sugguest a better way to do what I'm trying to do, that would be great!!!


    Thank you very much.
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    How exactly do you want to control the linear motor?
     
  3. zohonie

    Thread Starter New Member

    Dec 2, 2010
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    what do you mean exactly?
     
  4. mik3

    Senior Member

    Feb 4, 2008
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    Remove the word exactly and answer. :p

    I mean what do you want to do with the motor?
     
  5. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Motor specs would help in picking an H bridge IC. A 555 timer can control modulation frequency, to drive a toggle flip-flop which controls input polarity to an H bridge. To control travel , vary motor speed by controlling V to h bridge, analog or PWM.
     
  6. zohonie

    Thread Starter New Member

    Dec 2, 2010
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    the linear motor would be connected to a piston that would move inside of a cylinder to create suction (negative pressure). I hope that helps
     
  7. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    What is the length of travel?

    A "threaded rod" type setup, with the piston mounted on the "nut" would work, many DIY lathes use this approach for X/Y/Z movement.

    What force does the piston need to push or pull against in each direction?
     
  8. zohonie

    Thread Starter New Member

    Dec 2, 2010
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    the lenght of travel is will vary from 1-4 cm. The force is also very small. I didn't do to much calculations, but i would imagine it being in the range of 5-10 newtons.

    I'd like to find something that wouldn't require too much construction from my part, which is why i think the linear motor (actuator) is the way to go. what do you think?

    I was also thinking about some sort of pulsed vacuum generator, but I can't find anything of use so far.
     
  9. thatoneguy

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    How much vacuum do you need to create?

    What size enclosure will be evacuated and use this to stay at xx bar?
     
  10. zohonie

    Thread Starter New Member

    Dec 2, 2010
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    I would need to create about 0.196 bar in a 120 ml enclosure. Again, I would need to vary the pressure in a sine wave manner with 200 cycles per minute.
     
  11. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Instead of a linear motor could you use a regular motor with a offset crank pin and connecting rod to the piston? Kind of like a tiny engine with a electric motor running at the required RPM,to create the pulse frequency needed. The piston would move in and out of a cylinder creating the vacuum pulses you need, a small valve could be use on the chamber to adjust the vacuum pressure on with out changing the stroke of the crank.
     
  12. thatoneguy

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    This would work well. The way a jigsaw blade works, or a car engine piston. This would also give you a better approximation of a sine wave.
     
  13. shortbus

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    Maybe a better way instead of using a piston is to connect the motor to a rubber diaphragm sealed to the chamber. When the connecting rod push es the diaphragm in it gives the positive pressure wave. when the con - rod pulls out it gives the negative/vacuum part of the sine wave. The motor speed still controls the frequency.

    Using a diaphragm instead of a piston will eliminate the problem of getting the piston to seal in the cylinder.
     
  14. Bernard

    AAC Fanatic!

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    Not listed as a requirement by PO. Use a disc for crank with spaced tapped holes to vary crank throw. Or drive diafram with hi power speaker.
     
  15. shortbus

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    Why? One valve to set the '0' level of the pressure/sine wave. then the valve is closed. Then the in - out of the diaphragm would give the high/low pressure of the wave. Without worry of leakage past a piston or wear/scuffing on the cylinder.

    Mechanical fuel pumps on cars have used a diaphragm since the beginning of fuel pump use on cars. When used as a pump you need the valves, but not for this.
     
  16. beenthere

    Retired Moderator

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    Let's keep this the active thread, please.
     
  17. GetDeviceInfo

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    Best suggestion yet, a subwoofer sealed chamber.
     
  18. thatoneguy

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    Yes, I just noticed the 200Hz part. A sub is the perfect Linear Actuator for that frequency.
     
  19. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    200 cycles a minute equals 200 / 60 = 3.33333 Hz.

    Bertus
     
  20. shortbus

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    Plus with a speaker how do you create the vacuum the O/P needs?
     
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