DC motor turns both ways

Discussion in 'The Projects Forum' started by Adamf001, Oct 27, 2011.

  1. Adamf001

    Thread Starter Member

    Sep 5, 2011
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    Hi guys just wanted to know how can I get a DC motor spin clockwise then counter clockwise automatic in a circuit, I need this to be quite simple because I'mm going to use this for a Christmas decoration. is it doable? :confused:
     
  2. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    What is the motor's voltage and current requirements?Do you intend the direction of spin to be changed after a period of time, or by the position of whatever the motor is turning (i.e. limit switches). What is the motor turning? Does it need to stop before changing directions?..as motors don't like suddenly reversing directions under load.

    Ken
     
  3. chrisw1990

    Active Member

    Oct 22, 2011
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  4. Sparky49

    Active Member

    Jul 16, 2011
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    I don't think it would be very simple to do, but I would see about using relays to switch the current flow through the motor.

    I'm sure those who are more experienced than myself can help you more, but I'll see what I can do.:)

    Sparky
     
  5. chrisw1990

    Active Member

    Oct 22, 2011
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  6. samin

    Member

    Oct 14, 2011
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    There is a much-simpler way.. you can make the project with a double-pole double-throw switch and not use any relays at all. The only problem is the motor is constantly turning in one direction or the other. The alternative is to use two double-pole push switches or 4 switches as shown in the following diagram. You need to push both of the forward switches at the same time. By pushing the reverse switches very briefly you will get braking when travelling in the forward direction.
     
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  7. BMorse

    Senior Member

    Sep 26, 2009
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    Depending on the size and current ratings of your motor ( I am assuming this is a small decoration?? maybe a Tree ornament??) It can easily be done with a couple of NPN and a couple of PNP transistors (setup as an H-Bridge), coupled with the all too famous low power NE555 timer IC in an astable setup, you can set the delay (or how long it rotates in either direction) by just using 2 capacitors and 2 resistors.....

    Or

    You can still use a 555 timer to switch a DPDT (Double pole, double throw) relay via a transistor and just have it swap the leads of the motor to reverse the motors direction...
     
  8. BMorse

    Senior Member

    Sep 26, 2009
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    It is going to be used as a decoration, meaning it would be kind of tedious to keep having to push a switch or 2 to get it to move....
     
  9. chrisw1990

    Active Member

    Oct 22, 2011
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    only issue is, when your using switches is the cost, its ok, its simple, makes sense, but you dont really want a 10quid/dollar/(insert currency) motor with a 30quid/dollar.. switch?
    hence h-bridge, relays etc.
     
  10. Adamf001

    Thread Starter Member

    Sep 5, 2011
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    Well Im not sure about the motor, its a smnall one used for Toy cars, i wanted the motor to turn a arm on a santa decforation. i need the motor to turn one way for a second or two then stop, pause. then turn the other and then repeat the turns.
     
  11. BMorse

    Senior Member

    Sep 26, 2009
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    Well, in this case I would just use some mechanical attachment to move the arm, you can just have the motor turn one way without switching directions..... basically build a cam system that would move the arm back and forth if the motor is just left on, but then couple that with a 555 timer IC and a relay to turn on the motor say every 2 seconds to move for 1 sec, using simple machine techniques to build the arm cam should not be too hard, and you would only require a few components for the circuit to keep it simple....
     
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  12. chrisw1990

    Active Member

    Oct 22, 2011
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    555 slow oscillator? doesnt have to be precision.. could hook up a little transistor circuit or buy an hbridge ic.. should be fairly cheap for that size motor, and then get the 555 to toggle the direction? :)
     
  13. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Instead of a cam like BMorse, it would be easier to use a offset crank pin. Look at how windshield wiper motors work. http://auto.howstuffworks.com/wiper1.htm
    Then you just have to slow the motor down to the right speed.
     
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  14. BMorse

    Senior Member

    Sep 26, 2009
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    actually, (as I said) those widshield wipers DO use a cam to actuate :rolleyes:

    here is a quote from your link:

    FYI: Here is what wiki says about CAM's and Cranks:

    CAM
    CRANK
     
    Last edited: Oct 27, 2011
  15. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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  16. Adamf001

    Thread Starter Member

    Sep 5, 2011
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    Thank you guys, making a cam for the arm will be my best bet, thanks for all the help.
     
  17. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Not to argue with you but look at the animation in the link or the wiper motor in your car and see if it looks like a cam or a crank. The text is some times written by some one that doesn't really know what their talking about. :)
     
  18. BMorse

    Senior Member

    Sep 26, 2009
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    Not trying to argue either, but to turn a rotary motion to linear you use a cam, and to turn linear /reciprocating motion into a rotating motion, you still use a crank.... and by looking at the picture and my windshield wiper setup, it uses a cam to move my wipers (regardless if it it just a small rod coming off of the motor shaft), anything coming off of a rotating shaft that converts rotary motion into linear is a cam regardless if it looks like a crank..... that is just my understanding of it, and it is the only logical explanation for those terms. If you find a different meaning somewhere else I would be glad to say you I was wrong....;)
     
  19. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Any cam I've ever saw has a follower. Any crank has a connecting rod. A crank also has a pin that changes the rotating motion to another motion by the connecting rod. Since a windshield wiper uses a pin and connecting rod to make the movement and not a follower it where for is a crank mechanism. :)
     
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  20. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    IMHO...

    I tend to agree with Shortbus. a cam requires a follower; a crank is used to convert linear to rotary motion or vice versa.

    How big is your Santa?
     
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