Motor Control, and a few more ?s.

ALIBEALIBE Posts: 299
edited 2006-04-03 - 12:43:17 in Propeller 1
So, based on the little bit that I have seen, read and exchanged in this forum and no hands-on (yet), I am sold that Propeller is the best there is and will be out there and I'm personally very excited abt the chips and upcoming dev-board, etc.

I have a few implementation questions:

1. Motor Control
·· 1.1 Is Propeller capable of this inherently
·········· I might be wrong, but, I did not see threads on that and think that it does not support motor control inherently.
·········· One will need a H-Bridge circuit to hook up to propeller?
·· 1.2·Is there a MotorControl spin object in the pike

2. Battery voltage/power sensing
·· 2.1 Is this supported inherently
········I saw in the spec somewhere that there are power saving modes - but not sure

3. stepper motor
·· same questions as in 1.1, 1.2

4. Chip form factor and header board question
··· sorry about the following attached picture, but, I thought this would be a good example:
··· 4.1· Is parallax going to come up w/ something like this - a header board w/ propeller chip, crystal, voltage regulator, pins access - that can be plugged into our circuits.

5. Voltage Regulator
·· 5.1 Is this inbuilt.
···5.2 details on how to hook one up if it is not built in

thanks in advance

ALIBE

Comments

  • GadgetmanGadgetman Posts: 2,436
    edited 2006-04-02 - 13:55:16
    Well...

    1. I read somewhere that the I/O-pins can source/sink 50mA each(no mention of how many pins can do that at the same time, though) so in THEORY at least, you could use two pins as a H-Bridge to power one of those small DC-motors used for the vibrator-function in cell-phones. (They run at as low power as 20 or 30mA)

    I also don't see any problem of driving Steppers using just a ULN-type chip as you have the processing-power to spare to step it directly.

    4. As the Propeller is also available as a DIP, which only needs a 3.3V Voltage regulator (assuming that you're OK with the inbuilt oscillator, and I certainly am... ), there's not much need of such a module, is there?
    Besides, it will be difficult to place any of the SMT models on a DIP-like PCB, which would be the preferred choice as 40-pin IC-sockets are easy to place in any project, as the chip is too big for the width of the PCB.

    Of course, there might be a (small) market for a 'tower' design(additional PCBs on top) with a DIP40 footprint which has 3.3V-to-5V logic interface chips and is pin-compatible with the BS2p40?
    (A DIP24 to fit instead of a BS2/BS2e/BS2sx/BS2p24/BS2pe would be rather a waste of pins, unless the remaining 16 I/O-pins could be made accessible in some way, right?)

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  • Jon WilliamsJon Williams Posts: 6,491
    edited 2006-04-02 - 15:47:15
    Inherently is a loaded term.· Keep in mind that the Propeller is a general-purpose controller -- albeit a very special one.· Anything you can program in Spin or Propeller assembly is inherently built into the chip.

    1. You could use the cog counter modules for set-and-forget PWM; in fact, you could create an object that allows to to specify duty cycle AND frequency for best motor performance.· Andy and I have talked about this a bit.

    2. You can change the clock speed on-the-fly for power conservation.· With some simple interfacing, you would be able to detect a change in the outside world to initiate this change.

    3. Again, the Propeller is a general purpose controller -- doing stepper control would be very easy.· I can imagine an object that runs in its own cog that allows you to set a step rate for constant run, or another method that allows you to specify a number of steps, direction, and timing between steps.· Super easy -- heck, stepper control is easy with a BASIC Stamp.

    4. We're offering DIP, LQFP, and QFN -- the first two are hobbyist friendly, especially the DIP40 package.· You could make a module like the one you've pictured using the LQFP and the appropriate components ... might be a nice little side business for you!

    5. You must supply regulated 3.3v to the Propeller.· There is no magic to this, 3.3v regulators are common.

    Finally, despite the sink/source capability of the Propeller, I would NEVER connect any kind of motor directly to it.· Why risk a $25 microcontroller for a $2 motor when a $1 interface (ULN, L293, etc) will prevent problems....

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    Jon Williams
    Applications Engineer, Parallax
  • ALIBEALIBE Posts: 299
    edited 2006-04-03 - 12:43:17
    Jon, thanks for the detailed notes.
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