controlling a motor

Discussion in 'General Electronics Chat' started by kirit, Oct 14, 2008.

  1. kirit

    Thread Starter Active Member

    Sep 9, 2008
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    Given a motor, say from a cd player, how hard would it be for me to control it from a breadboard?
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. scubasteve_911

    Senior Member

    Dec 27, 2007
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    kirit,

    There are many flavours of motors, most of them require different methods to control them. I would assume a CD player contains, depending on model and what is being actuated, PMDC motors, brushless motors, or stepper motors. You need to identify what you are dealing with first, then figure out how to control it based upon what it is.

    Steve
     
  4. kirit

    Thread Starter Active Member

    Sep 9, 2008
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    Thanks you 2. Im going to dissect the cd player and tell you what I have. I guess it might be worth while to say what I want to do. Im going to slowly build a robot to take over the world!!!!!!! <insert evil laugh>

    Ok, maybe thats too ambitions, lets start as simple as possible.

    Build a breadboard that moves. Once we get that going, we can go further. Should I be looking at some particular type of motor? Id like to accomplish building a robot(breadboard robot) out of things that I have a round the house. THis will quickly be impossible as soon as I try to add some sort of programming. But that is down the road, I need to first accomplish movement.

    So you think initially using this type of motor a good idea?

    thanks.
     
  5. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    Small un-geared motors are pretty much useless for most robotic applications. Why not buy/ salvage a few motors and play around with them to get a feel for their characteristics. In terms of value and ease of use, small RC servos are pretty versatile. Either use as is or convert for continuous rotation.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Small pancake stepper motors can be had pretty inexpensively, and aren't terribly complicated to drive using a microcontroller.

    Jameco has a PF35T-48L4 stepper motor; they'll sell you 10 of them for $1.95/ea.
    http://www.jameco.com/webapp/wcs/st...=10001&pa=171601&productId=171601&keyCode=WSO
    You can drive them unipolar or bipolar; for beginners stick with unipolar mode.
    I've seen these same motors selling for $5 at other places.
     
  7. scubasteve_911

    Senior Member

    Dec 27, 2007
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    Actually, Small stepper motors are, in fact, quite useful for small robotics applications. Stepper motors are constant power and are designed for relatively small motions. The downfall of course, is that they will draw a constant power regardless of what is being used. This is inefficient for battery operation, but is definitely useful for proof of concept, etc.

    Gear motors can be quite inefficient too, since they usually rely on many reduction stages. Nothing is perfect :p

    Steve
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    Steppers have their highest torque at their lowest speed; as speed goes up, torque falls off rapidly. However, they're great for robotics - unless you want a sprinting speed demon; then it's time for a universal-type motor (brushed) and an H-bridge.

    Interfacing these low-voltage steppers to a microcontroller is easy - all you need is a single driver IC such as a ULN2803, which contains eight Darlington transistor drivers. One of those driver ICs could be used to control two of those stepper motors; and the ICs themselves are inexpensive. Jameco has them for $0.76/ea:
    http://www.jameco.com/webapp/wcs/st...toreId=10001&catalogId=10001&productId=34315&
    Then it's programming your uC to issue the stepping commands.
     
  9. kirit

    Thread Starter Active Member

    Sep 9, 2008
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    How much work/effort/time is involved in programing the uC? Any special equipment?
     
  10. scubasteve_911

    Senior Member

    Dec 27, 2007
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    Varies by microcontroller! I spent about 3 weeks learning the ARM Cortex microcontroller, but only 3 days to get started with the PSoC microcontroller. It also depends if you have any programming background, whatsoever.

    I can do a simple microcontroller project in a day, so once you get it down, it isn't a big deal.

    Equipment wise, you at least need a programmer. This programs the flash on-board and allows your microcontroller to run the program. A debugger is a handy tool to visualize what is going on inside the micro and to allow 'stepping' through code.

    I bought this a while back :
    http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=428-1585-ND

    A little bit pricey though for what it is. Something like the following might be fun to play with, and it is more current than the PSoC stuff. Apparently, PSoCs are supposed to have a bunch of new stuff coming out, it needs it bad.

    http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=DV164121-ND

    Steve
     
  11. kirit

    Thread Starter Active Member

    Sep 9, 2008
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    Yeah, thats a bit expensive. I dont have a problem spending it, as long as it will last me for awhile (1-2years).

    Eventually I want my breadboard robot to grow. I want it to have sensors (for example a camera), some way to control it through wifi/ethernet by a computer program.

    Will these programmers help me there?

    As a side node. Im not expecting to build this robot immediately. I figure that this is an excelent platform to help keep me motivated during my EE degree. Id love to have this become a robot I can enter in a competition in later next year. I was thinking the problem out and a robot really has 3 systems:movement, sensors, control. I think the movement part is the easiest. Im not looking to build the next best thing. Just start with A to B. Then I can add sensors, and later a control system. Then I'll upgrade the different systems as needed.

    So first things first, getting the breadboard to move. So it looks like we need 2 stepper motors, a uC, and a programmer. Im going to check with the EE tech for the labs and see if there is anything I can borrow/have to make it easier on my wallet.

    also, thanks for all the great input. I really appreciate all the help.
     
  12. scubasteve_911

    Senior Member

    Dec 27, 2007
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    kirit,

    I sadly went through many of my younger years in debt because of electronics. Although it would sound much cooler if I said it was spent at the bar picking up girls or something. It actually was one of the greatest investments I have ever made though!

    One thing about doing projects is that you learn a ton and don't forget the lessons learned very easily. You get used to the way design should be done and the general process. I ended up scoring a great job because of a summer work term I had. They were amazed that I was churning out the PCBs and code, which wouldn't have been possible if I hadn't spent the time and, unfortunately, money into the many projects I had attempted.

    That's cool that you want to enter a competition. I have always wanted to do this one, but haven't had time.

    http://www.trincoll.edu/events/robot/

    Are you going to buy a development kit? Try to get something modern, I'd stick with the PIC. Anways, we'll be around to help you out when you get your stuff.

    Steve
     
  13. SgtWookie

    Expert

    Jul 17, 2007
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    A camera would be very ambitious. Try starting with a line-following robot, using IR emitters and receivers.

    Camera data will require a huge amount of bandwidth to send frames at a reasonable rate. You would need a powerful uC dedicated to just that task alone.
    Consider it an "educational tool". Don't try to take on too much at first. Just getting a stepper motor to run forwards and backwards at a predictable rate for the first time can be a challenge.
    OK, so you have your three major functional blocks. Now you can start expanding on those blocks.

    Two steppers will get you rolling, if you use tricycle gear with the 3rd wheel a caster.

    Don't forget the driver IC's. ULN2803. You can also use ULN2003's, but those only have 7 outputs; so you'd need two of them to drive up to three steppers.
     
  14. bertus

    Administrator

    Apr 5, 2008
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  15. scubasteve_911

    Senior Member

    Dec 27, 2007
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    hey Bertus,

    May I kindly ask you if you have stock in "educypedia"? :p

    Steve
     
  16. bertus

    Administrator

    Apr 5, 2008
    15,645
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    Hello,

    No, but it is a handy site for all kinds of things.
    It has a lot of links and not only electronics.
    http://www.educypedia.be/
    There are pages for computer,electronics,hystory,human science and science.
    The pages in general and resources are mainly dutch.

    Greetings,
    Bertus
     
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