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Thread: Need help with PWM signal from Parallax Propeller

  1. #1

    Default Need help with PWM signal from Parallax Propeller

    Ok, so here's the background:

    I am a student of Reykjavík University, Iceland and am working on a project. The project is to make an AUV (autonomous underwater vehicle). There are 4 students in the project, none of whom have any experience with electronics at all. We have bought a Parallax - Propeller Servo Controller USB to use with five Devantech MD22 Motor Drivers to controll the thrusters on the AUV.

    We didn't really know what we were buying (we are really running low on time so we just went ahead and bought them) and now some people are telling us that the Propeller will not send out a PWM signal that can be used to control the thrusters, at least not with the default software on the chip straight from the box.

    What we need to know is:

    Is it possible for the servo controller to send out a PWM signal without changing the software on the chip. If not, then what software do we have to install on it and how :D

    Please forgive, my ignorance :)
    Last edited by ForumTools; 10-02-2010 at 04:54 PM. Reason: Forum Migration

  2. #2

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    Mmm, parallax has all the software written for this to get everything working. All you would need to do is to download the new code and program the chip using the prop tool.

    I believe some one has already done this. Not sure.

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    Nyamekye,
    Last edited by ForumTools; 10-02-2010 at 04:54 PM. Reason: Forum Migration

  3. #3

    Default

    I'd really suggest finding someone on your end that does know about electronics and programming. It is not trivial "off the shelf" stuff you're trying to do, unless you just want to run an umbilical back to some toggle switches and potentiometer dials, and use mode 1 of those versatile motor drivers.

    honestly, without an electronics guru, how do you propose to even get this to be autonomous?
    Last edited by ForumTools; 10-02-2010 at 04:54 PM. Reason: Forum Migration

  4. #4

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    You showed 2 motors controllers , and where are motors ? what the kind of motors ? maybe no need for H-bridge , maybe just some transistors TIP122 and resistors , it depends to your application , send please more information that other member of forum can reply to your need.
    Last edited by ForumTools; 10-02-2010 at 04:54 PM. Reason: Forum Migration

  5. #5

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    The motor driver you're using will accept standard servo control signals (RC mode) which is exactly what the Servo Controller will produce out-of-the-box. On the other hand, the Devantech motor driver is much more versatile than just a servo motor and can accept a variety of control signals. Depending on how you intend to control this vehicle, you may not need the Servo Controller at all or you could use it as the sole controller for the vehicle assuming you wrote the necessary control program for it.
    Last edited by ForumTools; 10-02-2010 at 04:54 PM. Reason: Forum Migration

  6. #6

    Default

    Kye said...

    Mmm, parallax has all the software written for this to get everything working. All you would need to do is to download the new code and program the chip using the prop tool.

    I believe some one has already done this. Not sure.
    I found something called Control of a DC motors with H-Bridge chips (LMD18 (5th one from the bottom), do you think that this is what I'm looking for?

    whicker said...

    I'd really suggest finding someone on your end that does know about electronics and programming. It is not trivial "off the shelf" stuff you're trying to do, unless you just want to run an umbilical back to some toggle switches and potentiometer dials, and use mode 1 of those versatile motor drivers.

    honestly, without an electronics guru, how do you propose to even get this to be autonomous?
    Originally there were supposed to be some electronics guys with us but they dropped out or something ... this is what I kept saying to my professors but they just said that we should just learn to do this ... like it was no problem ...

    At the end of this semester we are supposed to be able to remotely control it, just through an ethernet cable and next semester we will be getting an addition of 10-20 persons, some of whom have an electronic background. So what we have to do this semester, regarding electronics, is basically just to get the controller and drivers working with our thrusters.

    Laserist1984 said...

    You showed 2 motors controllers , and where are motors ? what the kind of motors ? maybe no need for H-bridge , maybe just some transistors TIP122 and resistors , it depends to your application , send please more information that other member of forum can reply to your need.
    We are using SeaBotix BTD150 thrusters (datasheet).

    Post Edited (karirafn) : 11/17/2009 9:14:34 PM GMT
    Last edited by ForumTools; 10-02-2010 at 04:54 PM. Reason: Forum Migration

  7. #7

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    Motors are DC brushed ,i think you need a H-bridge(to control Forward and Reverse) 5A for each motor and 2PWM from Propeller with different duty cycle, have a look to obect exchange motor control
    Last edited by ForumTools; 10-02-2010 at 04:54 PM. Reason: Forum Migration

  8. #8

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    Take a look at the "L293D test code" posting near here.

    It has sample code for motor control with an L293D chip.

    Let me know if you need a circuit to hook it up.
    Last edited by ForumTools; 10-02-2010 at 04:54 PM. Reason: Forum Migration

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