DC Motor direction controller help

Discussion in 'General Electronics Chat' started by jayci, Jul 19, 2009.

  1. jayci

    Thread Starter New Member

    Jul 19, 2009
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    Hello people, I am looking for some advise in building a DC Motor controller.

    What I would like to happen is when power is applied to the motor, it will rotate in one direction. Then when the power is removed for up to 3 minutes and then re-applied the motor rotates in the oposite direction. I want this to happen every time power is removed and then re-applied.

    Thanks in advance for reading my post.
     
  2. jayci

    Thread Starter New Member

    Jul 19, 2009
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    sorry, forgot to mention that it will be a 12 volt DC motor.

    spec'ed as
    SPECS:
    • Torque: 12.0kg/cm
    • Rated Voltage: 12.0V
    • Operating: 4.5 - 18V max
    • Current - No load: 70mA
    • Current - Full load: 1380mA
    • Gear Ratio: 244:1
    • Shaft Speed: 36RPM
     
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Here's an outline. A 555 is configured as a one shot and fires when power comes up. The three minute pulse output from 555 triggers a flip-flop on the leading edge and can not be retriggered for 3 min. The flip-flop changes state for every power on, so that Q out changes every other on, which controles a DPDT relay via a driver.With relay contacts cross connected , the motor will run one direction with relay on, and opposite direction when off.
     
  4. AdrianN

    Active Member

    Apr 27, 2009
    97
    1
    You need to invert the power applied to a DC motor if you want it to rotate in the opposite direction. Some logic could make this happen. You need an H-bridge. Then you need some logic and drivers to command each leg of the bridge to control the motor direction.

    With the H-bridge you can remove the power applied to the motor as well. Just command all the transistors to shut off.

    Do you know what an H-bridge is?
     
  5. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    You need a continuous 12V for logic to preserve " memory". What turnes the power off?
     
  6. AdrianN

    Active Member

    Apr 27, 2009
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    Indeed. And the logic can apply 12V to the motor in one direction, then turn off the power to the motor, then change polarity. As I understand it, the power needs to be turned off at the motor level, not at the controller level. Jayci, please clarify the project requirements.
     
  7. millwood

    Guest

    this can be easily done with a mcu: upon brown-out, the mcu will write its current direction into memory (eeprom or flash), and upon power up, it checks the prior direction and picks it up from there.
     
  8. millwood

    Guest

    alternatively, in the non-mcu world, you can use a capacitor to indicate direction. if the motor runs in one direction, you charge up the cap. if the motor runs in another direction, you discharge the cap.

    so if upon start, you check that capacitor to decide which way to rotate.

    just need to select the capacitor big enough to hold the charge over a period of time, during power off.
     
  9. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
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    If you give us details about the problem you're solving, there also may other strategies for solving the problem that are simpler, more reliable, and/or have smaller parts count.

    Thus, for example, I'm building a door opener/closer for our chicken coop (we have predation from foxes and raccoons) and I'm using a DC motor for the door (I'd much prefer an old reversible Bodine AC gear motor, but I haven't been able to find one). The way this thing will work is a 110 VAC timer will turn on in the morning to open the door. This will energize a DPDT relay; the motor runs until it activates the SPDT stop switch. Then, in the evening, the timer will turn off the relay; this causes the DC motor to run backwards, closing the door until another limit switch is hit. If I had an AC gearmotor, the total parts count for this would be: one DPDT relay, two SPDT switches, the timer, and the motor. Very reliable. Everything would come out of my junk box if I had the motor.
     
  10. AdrianN

    Active Member

    Apr 27, 2009
    97
    1
    Nice project Someonesdad. Please post some pictures when the project is done. Or, some pictures with the progress. I am contemplating to build something similar for my cat's door.
     
  11. jayci

    Thread Starter New Member

    Jul 19, 2009
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    Thanks for the input people. The motor is on a 1metre track. When it hits one end of the track, i am wanting the motor to stop for a user defined period of up to 3 minutes and then carry on to the other end of the track and repeat.

    The current setup is using a AC Synchronous motor and using the fact that when the motors stills at one end it will change direction. I don't think the Synchronous motor will last long with that kind of abuse.

    Burnards example seems good for my situation, becuase I already have the 555 timer doing the pusle to a relay. I just need to know about the flip-flop thing, is it a circuit or a component.

    And I don't really know what a H-bridge is.
     
  12. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    The plot thickens. The FF is an integrated circuit [IC], like a CD4013BC, a dual D type FF. An H bridge is something like a solid state DPDT cross-strapped relay, lots of information in AAC. Does the " cart" obtain power from track or a dangling coil cord. Do you want all control on "land" and only motor on cart, with reversal of track polarity?? Last question-WHY?
     
  13. jayci

    Thread Starter New Member

    Jul 19, 2009
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    The cart is getting it's power from dangling coil cord. But when I upgrade to the DC motor, I'll have a battery, motor and cart all in one. All control on the cart is best. The cart is for a promotional display that goes back and forth on the track all day.
     
  14. knaaphix

    New Member

    Apr 1, 2009
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    IS it for a washing machine direction controller ?
     
  15. jayci

    Thread Starter New Member

    Jul 19, 2009
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    No, it is not for a washing machine direction control. It is for a cart with DC motor going back and forth with user predefine stop period of up to 3.5 minutes at each end of the inert track.
     
  16. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    'Missed your post yesterday, link was down all day; but all is not lost, print shows logic on land, but it can all be shoved in cart, including SW 1 & SW 2. The delay time is controled by C2, R4 & R5.[ R5-1k, R4-1M,C2-3μF, etc].Each time that a switch is bumped the 555 is given a start pulse, the inverted output inhibits gates C & D for 3 min.The state of the FF[IC-F]is determined by which SW was bumped, which then determins direction of cart. Outputs A & B go to an H bridge which drives motor.Now someone will come along and say that ICF not needed, you have spare NOR gates to make a R-S latch. An example of an H bridge is @ http://www.solarbotics.net/library/circuits/driver_4varHbridge.html It would need to be beefed up to handle your motor, maybe HELP! will be forthcoming.
     
  17. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    On a 1 meter track, probably not a verry large cart, so motor is not likely to be heavily loaded-maybe 100 mA? The referenced H should work as it stands..
     
  18. jayci

    Thread Starter New Member

    Jul 19, 2009
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    Thank you for your help Bernard. What would the value of R1 and R2 be? And also is IC A NOR Gate and IC B, C, D are NAND gates. Would a 74HC00 Quad 2-input NAND Gate IC be suitable?
     
  19. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Looks like R1,R2 got lost, I'd use 9.1k because my bag is full of 'em, any thing 10k to 47k should work. 74HC00 is good. I would replace 4013 with two NOR's, IC-B with NOR, parallel two sets of NAND's[ like IC-B with IC-C, pin 1&4; pin 2&5; 3&6 ]. The paralleled outputs will give greater drive capability.
     
  20. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Revised version.
     
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