what do i need to make a motor turn cog 360 degrees

Discussion in 'Electronics & Electrics' started by Gooliez, Apr 17, 2015.

  1. Gooliez

    Gooliez Member

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    Ok, so simply put, i have 2 cogs, 1 460mm in Diameter, second about 130mm

    i would like to set up a motor that when i press a button ( momentary ) it will rotate the small cog enough to have the large cog do a single 360 degree rotation...

    electronics, i have very basic idea on, so simple explanation would be appreciated. just need a list of what i would need and if you have links on the exact item would be even better....

    the cogs are made out of pine ( cut with a CNC) so they are pretty light.

    thanks for your help !
     
  2. paulvk

    paulvk Member

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    Very simple you need one micro switch, a push button and a switch for on-off
    Put a little bit of wood on the cog when this hits the micro switch it turns off the power to the motor
    The push button goes accross the micro switch so when you push it it starts the motor which takes the wooden block past the micro switch so it continues to rotare until it again reaches the micro switch
    The other switch is to turn it off/on.
     
  3. rainwulf

    rainwulf Member

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    Yea this could be done with a micro switch, and a normal switch. The micro switch is normally on, but can be turned on with a peg in your gear.

    The normal switch is across this micro switch.

    Press the normal switch, the motor turns, allowing the micro switch to release and stay ON, until it gets hit by the peg again.
     
  4. 2xCPU

    2xCPU Member

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    I can think of lot way to solve a problem like this depending which parameters are important, starting with the precision of the "360°".

    For a low precision solution, you could just use a timer to cut power after an elapsed time.
    A stepper motor controlled by a string of decade counters or a small micro.
    You could drill a hole through the gear and mount an LED on one side and a photo-receptor on the other (or use a reflective strip and do it all from one side). Similarly you could drive a nail into the gear and use a hall effect sensor to detect it going past.

    However, without a doubt, the suggestions above will get you going much faster and probably much more reliably.

    A microswitch with a roller-follower is probably what you are after.

    2.
     
  5. @rt

    @rt Member

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    It looks best to have options.
    Depending on the rest of the machine and motor, and the speed it runs,
    I can imagine the easiest solution possibly overshooting the microswitch
    and powering the motor again, able to repeat forever.
     
  6. 2xCPU

    2xCPU Member

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    An easy way around that problem is to use a double pole relay to prevent the possibility.

    2.
     
  7. paulvk

    paulvk Member

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    If you use a micro switch with a leaver it should not over shoot.
     
  8. OP
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    Gooliez

    Gooliez Member

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    ok great start...

    i forgot to mention that the large cog will be enclosed. so i cant really attach anything to that.

    so i'm guessing a timer will be the best ?
    the large cog doesnt have to turn at a ridiculous speed, maybe take around 5 seconds to do a full turn.

    so what motor would i be looking at ? something like a CNC motor ?
     
  9. RobRoySyd

    RobRoySyd Member

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    A timer controlling a simple DC motor could be the best or worst possible solution because you haven't revealed the most important factor. How accurately does the big cog have to complete one revolution i.e. does it have to stop at a fixed position each time or is that not important?
     
  10. SLATYE

    SLATYE SLATYE, not SLAYTE

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    And how consistent is the load on the motor, and the power supply?

    A timer will probably do a fairly good job if the load on the motor is constant and the power supply is consistent. On the other hand, if you set it up with no load and then hang a big fan off the end of the gear, it'll only go half as far. If you run it from batteries, then it'll travel less distance as the batteries go flat.

    If you need consistency regardless of power supply and load, then a timer won't work well. The two standard options are a stepper motor (a bit tricky to drive, but can provide exact positioning fairly cheaply) or a normal DC motor plus an encoder (easy to drive, but relatively expensive and potentially hard to control).
     
  11. OP
    OP
    Gooliez

    Gooliez Member

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    ok, i'm home now, taken a photo of the cogs.... now i can explain better.


    Click to view full size!


    i'm experimenting on making a "Paintball counter" the large cogs has 100 holes in the middle for the paintballs to drop into. this rotates and when it reaches a certain point, say 340 - 360 degree part.... there will be a hole below, where the paintballs drop.

    i want to replicate this, ( something a lot cheaper )
    https://www.youtube.com/watch?feature=player_detailpage&v=3AKrzgUSsoA#t=254

    so as you can see, it doesnt have to be flat out speed wise, and i dont want a continuous running, just press a button and counts out 100 balls then stops.
    but it will have to technically go back to a reset position. otherwise it will end up being inaccurate and miscount balls

    if i can run it without the small cogs, even better. the timber is pine, so nice and light, may need to get some bearings for it ( when i can get the initial setup running)

    hopefully all this info can help you guys with what you need to know
     
    Last edited: Apr 18, 2015
  12. RobRoySyd

    RobRoySyd Member

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    You can easily put a reflective sticker on the big cog and use an optical detector to stop a DC motor at a fixed position.
     
  13. OP
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    Gooliez

    Gooliez Member

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    so do i need a stepper motor, pcb board ? like i said, i know very little and hardly know what you guys are talking about....

    links would be great...

    i do actually have a microswitch with rollover laying around left over from my CNC kit... so that would be a start
     
  14. paulvk

    paulvk Member

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  15. SLATYE

    SLATYE SLATYE, not SLAYTE

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    How are you planning to drive this? If it'll be using an Arduino (or similar), it might be worth just using a 360 degree servo (or redesigning it to use a 180 degree servo, or a standard 90-ish degree one). That avoids having to build any high(ish) current motor driving hardware.

    The other easy option I can see is something like this. Put the big cog on one shaft, put a cam/microswitch on the other shaft.
     
  16. OP
    OP
    Gooliez

    Gooliez Member

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    like i said, i have no idea, thus coming to you guys.

    that 90 degree geared motor, would that be strong enough to rotate the cog ?


    can i buy a board of some sort, attach everything to it... eg, Power / motor / button and then program it. is there a board that exists like this ? or do i have to but multiple boards to do it....( like project below )

    i found this, kinda the same theory... press a button, the machine finishes off the command, then resets and ready to go next button press.
    https://www.youtube.com/watch?v=Pz8hdHnlGOk

    project here
    http://www.instructables.com/id/Robot-Foam-Cutter/

    this is the closest to electronic wise i can find of what i'm after ( not that i really know what i'm looking for )
     
  17. OP
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    Gooliez

    Gooliez Member

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    i just weighed the large cog, it weighs 1kg.... obviously if it was on bearings etc, the motor wouldnt be supporting the full weight
     
  18. imgod22222

    imgod22222 Member

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    actually, recently sparkfun released a product they call a servo trigger--that may do exactly what you want without an arduino.
     
  19. RobRoySyd

    RobRoySyd Member

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    I'd look into using a lazy susan bearing to support the large cog.
     
  20. OP
    OP
    Gooliez

    Gooliez Member

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    checked it out
    https://www.sparkfun.com/products/13118
    looks good, i'd have to redesign the whole cog though, and i think the return to start ( going back the same way it just came from ) might slow the process down too much

    Great idea !
     

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