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Propeller Stepper Driver — Parallax Forums

Propeller Stepper Driver

GeeksGoneBadGeeksGoneBad Posts: 100
edited 2011-07-03 14:38 in Propeller 1
Hi all! I've had just a little success getting a stepper motor to move with my Propeller - this will probably seem quite simple to most of y'all but I wanted to share anyway :)

I am using the propeller and a L298 and that's about it (there are a couple of caps per the L298 datasheet)

I made a video :)http://www.backyardworkshop.com/blog-posts/electronics/98-parallax-propeller-stepper-driver.html
and this is a second video to one where I was playing with a stepper with some buttons

constructive feedback is encouraged :)

Comments

  • ElectricAyeElectricAye Posts: 4,561
    edited 2010-12-22 06:13
    Very nice! You're stepping up in the world.
    It's liberating when you find out you can make things move with electronics.

    Next thing to try: check out some microstepping techniques to smooth out the stepper motion. :)

    http://forums.parallax.com/showthread.php?126523-Microstepping-a-motor-with-the-Propeller-and-PWM


    Have fun!
  • StefanL38StefanL38 Posts: 2,292
    edited 2010-12-22 07:04
    Hi,

    of course it is fun to create something from scratch.
    Just as an additional option: there is another chip that works together with the L298. It's the L297.
    The L297-chip does two things:

    1.)
    Chopping the current of the stepper-coils on/off with an adjustable current.
    Thruogh chopping the current you can use higher voltages without exceeding the current-limits of the steppermotor.
    The result is more torque and a high maximum rpm where the motor is not stalling.

    2.)
    Simplifying the logic to drive the steppermotor. You just need a step-pulse and direction input.
    All the details in wich sequence the coils have to be switched or change their polarity is done
    by the L297. It also offers halfstep-mode. But this chip can't domicrostepping.

    STM has a app-note
    STEPPER MOTOR DRIVE CONSIDERATIONS, COMMON PROBLEMS & SOLUTIONS

    http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/APPLICATION_NOTE/CD00003771.pdf


    You should by a switchmode powersupply of 500mA for the propeller-chip and one with 2A or 3A for things like motors
    They will pay off after 5 batteries and then save money.

    best regards

    Stefan


    edit: some app-notes about stepperdriving
    http://www.st.com/internet/com/search/search.jsp?q=L297%20datasheet&entqr=3&entsp=a&output=xml_no_dtd&sort=date:D:L:d1&client=ST_COM_PlanA_frontend&ud=1&oe=UTF-8&ie=UTF-8&proxystylesheet=ST_COM_PlanA_frontend&site=ST_COM
  • GeeksGoneBadGeeksGoneBad Posts: 100
    edited 2010-12-22 07:35
    Thanks for the links guys - I will check them out!

    I am looking at some power supplies - you mention a 500ma PS for the prop - do you have any recomendations?

    Thanks!
  • StefanL38StefanL38 Posts: 2,292
    edited 2010-12-22 08:14
    Hi,

    for supplying the propeller the voltage shouldn't be too high. (7.5V)
    with higher voltages the 5V and the 3.3V regulator have to dissipate to much heat.

    So this one from parallax would be good http://www.parallax.com/Store/Accessories/PowerSupplies/tabid/165/CategoryID/39/List/0/SortField/0/Level/a/ProductID/73/Default.aspx
    For the propeller itself it will be eonough to have a 300mA-type. propeller 30-50mA plus some LEDs.
    Any similar type from any other shop with 7.5V 300mA to 500mA will be good too.
    Stabilised wall-plugs of the old type with a transformator will do too.

    If you want to use a power-supply with a higher voltage you should build a cascade of regulators 12V, 8V, to keep the powerdissipation small in each regulator
    caclulation example
    Inputvoltage 12V Outputvoltage 5V (=voltagedrop across the regulator 7V
    0.8A * 7V = 5.6W. This would heat up a 1A TO220-housing regulator a lot even if it's mounted on a cooling-aluminium.
    Guess the regulator will even go into temperature shutdown-mode to protect himself from getting fried.

    If you want to drive motors hobbyservos, steppers etc. you need more current.
    If you drive steppermotors with a chopper-current-limiting circuit the voltage can be as high as the H-Bridge-Chip can deal with.
    The L298 can do maximum 46V.

    best regards

    Stefan
  • TtailspinTtailspin Posts: 1,326
    edited 2010-12-22 10:48
    Super cool Prop Board setup, all kinds of buttons, dials, and gauge's in one little compact space.
    Now that You have mastered the button's, It is time to make that volume control into a speed control,
    and that fancy variable resistor into a direction control...
  • Cluso99Cluso99 Posts: 18,069
    edited 2010-12-22 11:45
    Pololu have a small stepper pcb based on the Allegro A4983 which will drive the Nema 17s up to 2A 35V as used in the RepRap project. This is even simpler to drive and has a current limit setting. http://www.pololu.com/catalog/product/1201
  • bennettdanbennettdan Posts: 614
    edited 2010-12-22 16:04
    GeeksGoneBad
    The ST has a stepper driver chis that has microstepping and it comes in a DIP format so its easy to breadboard the L6208 it has a max 56 volt input and 5.6a output.
    Here is a App note that shows how to set it up for step half/step and microstep.

    http://www.st.com/stonline/books/pdf/docs/8607.pdf
    Digikey has them but are a little pricey
  • ElectricAyeElectricAye Posts: 4,561
    edited 2010-12-22 18:45
    Cluso99 wrote: »
    Pololu have a small stepper pcb based on the Allegro A4983 which will drive the Nema 17s up to 2A 35V as used in the RepRap project. This is even simpler to drive and has a current limit setting. http://www.pololu.com/catalog/product/1201

    Cluso,
    this is a very interesting suggestion. But I'm wondering about its ability to drive all the way up to 2 Amps. The website says:

    Power dissipation considerations
    The A4983 driver IC has a maximum current rating of 2 A per coil, but the actual current you can deliver depends on how well you can keep the IC cool. The carrier’s printed circuit board is designed to draw heat out of the IC, but to supply more than approximately 1 A per coil, a heat sink or other cooling method is required.

    How would you get a heat sink onto it? Is there some kind of heat sink you can glue directly to the chip? Or is a cooling fan the only way to go?
  • Cluso99Cluso99 Posts: 18,069
    edited 2010-12-22 20:16
    No, head the warning! Trying to cool the chip is not easy although things like this have been done. Fan, tape heatsink, etc.
  • GeeksGoneBadGeeksGoneBad Posts: 100
    edited 2011-06-15 06:10
    Not sure if anyone is monitering this :) but I have switched to the pololu A4983 - I also tried the Easydriver from Sparkfun

    Here's a link to the current (and ongoing) project - but I do have the SPIN code for driving the Easydriver OR the A4983 in my downloads if anyone is interested too :)

    http://www.backyardworkshop.com/blog-posts/electronics/97-homemade-power-drive.html
  • Paul Sr.Paul Sr. Posts: 435
    edited 2011-06-15 09:39
    I have been watching and waiting for your update. How is the Pololu working out in place of the Easydriver?

    Does the code you have for the Easydriver work with the Pololu without change (being lazy, here!!)
  • Cluso99Cluso99 Posts: 18,069
    edited 2011-06-15 13:05
    The pololu A4988 is a better version as it has short circuit protection too. Beware, the A4988 is in short supply!
  • CPWH1CPWH1 Posts: 1
    edited 2011-06-25 22:26
    Has anyone tried using the Step Genie ( http://www.stepgenie.com ) chip with the propeller chip?
  • GeeksGoneBadGeeksGoneBad Posts: 100
    edited 2011-07-03 14:38
    Just another update - Initially the Pololu board was also not enough to drive the lathe - but I figured it HAD to be so I tried out a new stepper motor (bigger) and now it works pretty good

    I bet it would have worked good with the easy driver too and the larger stepper but I'll have to test that theory out

    as it stands the Pololu board and bigger stepper are working good :) - I posted a video here: http://www.backyardworkshop.com/blog-posts/electronics/97-homemade-power-drive.html
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