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Some questions — Parallax Forums

Some questions

SMSM Posts: 3
edited 2006-03-30 16:13 in Robotics
Hi,

I'm a beginner in robotics and want to know some things before spending money.

As far as I know you need a Motor-Controller to connect a DC motor to the Boebot.
-Do I need one too to connect two Servosto the Boebot-board?

-Can I connect the battery pack (from the Boebot) / a DC Motor (540 Motor) / 2Servos / to the Parallax Professional Development Board?

-Is it a good idea to use the Professional Development Board for a robotics project?

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Ps: Thank you for answers

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2006-03-29 15:40
    No, you can drive the BOE-Bot servos directly -- that's how it's designed.

    You can connect things to the PDB, but its not designed to be mounted on anything and you'd need a platform much bigger than the BOE-Bot to hold it.

    The PDB is a great platform for project development. If you have a mobile platform big enough to hold it, then I'm sure you could in fact use it in that manner.

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    Jon Williams
    Applications Engineer, Parallax
  • SMSM Posts: 3
    edited 2006-03-29 18:40
    Hi,
    Thank you for the fast answer.
    I have a plattform big enough to carry the PDB,
    I only need some answers to the second line to confirm what i think, because i'm not totally sure about the specifications
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-03-29 18:52
    SM,

    ·· You will likely need a bigger (more current capacity) battery pack to handle the increased load and current draw.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • LSBLSB Posts: 175
    edited 2006-03-30 01:32
    SM,
    I'd like to add to the answers you've gotton so far because I too am a beginner and eager to share what I've so recently learned.
    All motors require a driver to work with a microcontroller. I imagine the signals that come from the pins of a BS like nerve impulses--they send (or receive) messages, but no power. Servos have 3 wires; two carry power direct from the battery to a circuit inside the servo. The third wire carries the signal that tells this circuit what to do--like a nerve tells a muscle. Servos were developed for R/C applications and have small motors that require only a little power to make them work. Other motors were developed for different applications and have more power, but don't have the internal circuitry. It is necessary to provide an external driver and more or bigger batteries to run them for the same amount of time.

    LSB
  • allanlane5allanlane5 Posts: 3,815
    edited 2006-03-30 16:13
    The really nice thing about a "modified servo motor" is that MOST of the drive electronics are inside the Servo itself. The interface to your BS2 is that 'Signal' pin, which you give a 1.0 to 2.0 mSec pulse to, repeated every 20 to 50 mSec. The modified servo compares your pulse to a 1.5 mSec reference value inside the servo. If your pulse is less than that, the motor runs one way. If your pulse is greater than that, the motor runs the other way. If your pulse equals that, the motor stays still.

    And there's a variable resistor inside the Servo you can 'tweak', to insure it's at 1.5 mSec.

    So, a modified servo makes an inexpensive motor, which requires NO additional external circuitry (besides the BS2 running PULSOUT) to make it work.
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