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12VDC Motor Control Help

Discussion in 'Sensors and Actuators' started by mooginnyc, Apr 12, 2010.

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  1. mooginnyc

    mooginnyc

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    Feb 3, 2010
    Hello,
    For a project, I'm trying to create variable speed for a DC motor at 12V. The motor
    is an EG-530AD-2F. I tried this circuit:
    http://www.eleccircuit.com/wp-content/uploads/2009/08/12v-dc-motor-speed-controller-by-4011.jpg
    and I was able to control a smaller motor using a 9V source (not sure the motor rating), but I was unable to get any speed response using the EG-530AD-2F.

    Does anyone have any idea why this circuit wouldn't work with this motor? I also looked up the EG-530AD-2F on this forum, and saw a post where someone was looking for a replacement motor control IC for a similar motor a couple of years ago.

    Here's the data sheet of the motor I'm using:
    http://www.ewinson.com/image/draw/eg530ad.pdf

    Are there any recommended 12-15v motor control IC's? For sake of real-estate, having a single chip and variable resistor would actually be best. I'm running out of room in the project case with all the other circuits!

    Thanks a lot!
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I'm not surprised it doesn't work. It uses a 1000uF resistor!

    I also don't get how that oscillator works, and I wonder what family it is given the supply rail. Is it 4000 series CMOS? Even with that I'd expect the supply rail would exceed their absolute maximum ratings.
     
  3. mooginnyc

    mooginnyc

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    Feb 3, 2010
    That's funny.. I didn't even catch that about the 1000uF resistor! Yes, it calls for a 4011 IC
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    So, what did you use for the 1000uF resistor?
     
  5. mooginnyc

    mooginnyc

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    Feb 3, 2010
    A 1000uF capacitor :)
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Hmmm, I'm not sure what a capacitor would be doing there. A 1K resistor might make more sense, but I can't figure out how the oscillator osculates.

    Using an even number of gates is poor design. OK, it looks like this. That is definitely the 2 gate oscillator *NOT* recommended by NS. And it confirms the 1000uF resistor is in fact supposed to be a resistor.

    I would not be surprised if the circuit fails to work because the supply voltage is too high (it must be around 18 volts or more when the motor is not running) OK, for 4000B series CMOS the max voltage is 18 volts -- you might just be squeaking it in.

    I'd replace the 1000uF capacitor with what they probably meant -- a 1000 ohm resistor.
     
  7. mooginnyc

    mooginnyc

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    Feb 3, 2010
    Okay, I'll give that a try. There was some oscillation, because I could here it on the first motor. In fact, it sounded (very quietly ) like a modulating pulse wave on a synthesizer. But not on the second motor.

    Also, I realized I posted this to the wrong category! How do I change it? This isn't for a microcontroller.

    So, any single chip solution for a 12VDC motor? I know there are pwm IC's for motor control, but I've never used one.

    Thanks for the help!
     
  8. mooginnyc

    mooginnyc

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    Feb 3, 2010
    So yesterday I came across an L293d, H-Bridge. Looks like it's meant for motor direction, not speed. But what if I send a send a square wave to the logic pins? Could the frequency of the square oscillator govern the speed?
    http://focus.ti.com/lit/ds/symlink/l293d.pdf
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    No, the frequency won't affect the speed. What you want to do is vary the mark/space ratio of the signal.

    Essentially you want to alter how much of the time the motor is turned on, from say 1% to 99%. As you increase this the motor will turn faster and faster.

    A 555 is a good chip for this and you should be able to find plenty of circuits where the mark/space ratio can be altered without changing the frequency The output of the 555 can be used to drive the transistors used in your original circuit. You would have to provide a stabilized voltage for the 555, but you can do that with either a zener diode (and resistor/capacitor) or a low power three terminal voltage regulator (and a couple of capacitors).

    Look on this page.
     
  10. mooginnyc

    mooginnyc

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    Feb 3, 2010
    Oh, like PWM? I do have a bunch of 555's around. Maybe I'll try that. I guess first I'll replace the 1000uF capacitor with the resistor on the other circuit (since it's already breadboarded) just to see if it works. The L293 was given to me by someone yesterday, coincidentally as I was reading about them. Thanks for the help!
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Yeah, that circuit you have is also trying to do PWM, however it's not done a way that I'd do it. A 555 is probably a better approach.

    You should try to ensure that the power to the 555 is regulated a little :) There are many different types, but the datasheet I pulled up suggests a max supply of 16V. You probably need to isolate the 555 from the noise that the motor might put on your power supply.

    Also you'll need a resistor in series with the base of those transistors to limit the current. Try 1K to start off with.
     
  12. mooginnyc

    mooginnyc

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    Feb 3, 2010
    Cool thanks. For the entire project, I have 12V coming in, and then I regulate to 9v and 5v rails for the rest of the circuits. Would powering the 555 from the 9v rail, and the motor on the 12v be adequate isolation? The motor is running off the 12V supply anyway.
     
  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Yes, that should be a good option. The input to your 9V regulator should probably be partially isolated from the 12V rail if the motor is running from it.

    A diode and a capacitor will help ensure that the input to the regulator stays reasonably stable. Just make sure you have sufficient margin to allow good regulation.

    Because the transistor is switching the ground lead of the motor, the reduced voltage for the 555 will not cause any problems.
     
  14. mooginnyc

    mooginnyc

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    Feb 3, 2010
    Hey.. so I finally built the 555 circuit for the motor, and it's doing something weird! I combined the two schematics on this thread. I built the 555 part for the pulse oscillator, but instead of using a BUZ11 transistor between the motor and ground, I used the BC549 and TIP41 darlington pair like on the 4011 schematic. I also used the regulated 9v for the 555 circuit supply rail, and kept the motor on the 12v rail. And I used a 1N4148 diode across the motor instead of the MBR1645.

    It's not changing the motor speed, but it's definitely creating a variable pulse wave. I hear it very loudly through the audio output. I'm measuring a frequency of about 263Hz. Turning the pot sounds like it's changing the pulse width (sounds like pwm on a synthesizer, in fact a pretty good sounding pwm, but not what I want!)

    Any reason this is bleeding to the audio output and not changing the motor speed? Everything appears to be hooked up correctly.

    Thanks for the help!
     
  15. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Just so I don't have to guess, show me the circuit you're using now.
     
  16. mooginnyc

    mooginnyc

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    Feb 3, 2010
  17. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    If you connect a LED and series resistor in place of the motor, does it dim as you adjust the duty cycle?
     
  18. mooginnyc

    mooginnyc

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    Feb 3, 2010
    I'll give that a try..

    I'm curious how the wave makes its way to the audio output? Basically, I'm trying to control the speed of a 12v motor in a cassette player. The motor, and the cassette player run on 12v, and then I have a regulator for 9v off the 12v supply. That's how I'm running the 555 circuit. Also, the motor only operates when one of the cassette buttons is mechanically engaged. The audio output and the 555 circuit do share ground.

    Thanks!
     
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