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Thread: Motor driver

  1. #1
    Senior Member Cyborg sudarshan's Avatar
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    Default Motor driver

    Hi everyone

    i am looking for a solid state motor driver with pwm and ablitiy to drive motor 10A -20A 12V. for my war bots. i am not looking for ready made boards. i am looking for circuit diagrams.

    can anyone suggest me some. i have googled a lot but i dont seem to find simple ones. i find only very complex stuffs.

    thanks in advance.
    BY
    Sudarshan Anbazhagan,
    SuperBotics MultiTech Pvt. Ltd.

    http://www.superbotics.com
    http://www.getahost.in

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  3. #3
    Senior Member Cyborg sudarshan's Avatar
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    thats looks great

    but still one question . will a i be able to reverse the direction when i am using pwm. because i have never worked with pwm for motor controls. The video in thier site shows pwm control in only one direction.
    BY
    Sudarshan Anbazhagan,
    SuperBotics MultiTech Pvt. Ltd.

    http://www.superbotics.com
    http://www.getahost.in

  4. #4
    Senior Member Cyborg sudarshan's Avatar
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    Default pwm

    thats looks great

    but still one question . will a i be able to reverse the direction when i am using pwm. because i have never worked with pwm for motor controls. The video in thier site shows pwm control in only one direction.
    BY
    Sudarshan Anbazhagan,
    SuperBotics MultiTech Pvt. Ltd.

    http://www.superbotics.com
    http://www.getahost.in

  5. #5
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    Default

    yes but for that you will have to use two PWM pins for each motor.

  6. #6
    Senior Member Cyborg sudarshan's Avatar
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    ok thanks still one more question

    how many pwm channels does atmega32 offer ?

    i need to control atleast 2 motors (4 ch pwm) and atmost 4 motors (8ch pwm) . if atmega32 doesnt which can

    thank you
    BY
    Sudarshan Anbazhagan,
    SuperBotics MultiTech Pvt. Ltd.

    http://www.superbotics.com
    http://www.getahost.in

  7. #7
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    Default

    I have never used atmega32 but i think it has 4 pwm pins.
    Atmega328 has 6 pwm pins.

  8. #8
    Senior Member T-1000
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    I don't know where the 2 PWM pins for motor reversing come from, but you could use an h-bridge using discrete MOSFETs. Its not too complicated.

    In Microchip uCs, you have a module called Enhanced CCP. It has 4 pins on one of the ports dedicated to PWM driving of the gates of the 4 MOSFETS of an h-bridge. Check for something equivalent in Atmegas. This module takes care of running the motor, reversing it, inserting dead-band delays while reversing direction, etc.

    You'll also need some some MOSFET drivers to ensure that the MOSFETs are driven hard while PWMing. Because at high switching speeds, uCs pins cannot provide the current needed to ensure that the MOSFETs don't spend too much time in the linear zone.

    See this:
    "http://www.cnczone.com/forums/open_source_controller_boards/18028-discrete_transistors_avr_microcontroller.html"
    --
    Mohit Mahajan,
    www.BioZen.co.in

  9. #9
    Senior Member Cyborg sudarshan's Avatar
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    Default

    check this one
    http://robokits.co.in/shop/index.php...468885998e746a

    it seems to be using tip122 and tip 127 for driving upto 5 amps and they seem to ressemble the above mentioned circuit except they use tip 142 and tip 147 which drives 10 amps.

    so can anyone suggest me how can drive motors bi direction with pwm using 1 ch or 2 ch . 1 ch will be better
    BY
    Sudarshan Anbazhagan,
    SuperBotics MultiTech Pvt. Ltd.

    http://www.superbotics.com
    http://www.getahost.in

  10. #10
    Super Moderator T-1000 docel's Avatar
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    Simply speaking, connect same type transistors in parallel to increase the total current.
    There are limits to this though.
    1. You can easily drive by adding another transistor in parallel
    2. The drive transistor or circuit must be changed to higher current if you add more than 1 transistor in parallel to the existing bridge circuit.
    3. A series base resistor must be added, similar to each transistor. Anywhere from 100ohms to 4.7k ohms depending upon the drive transistor rating. the thing is to use a higher value and keep reducing till you get good current drive.
    4. Mosfets are better than Bipolar transistors.
    5. Bridge circuits are a potential fire makers, more so high current bridge circuits. Be careful or you'll burn the house up. Also , make sure your drive logic is true - 00, 10, 01 ONLY.....dont drive home made bridges with a logic 11.
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

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