Power Supply 40v 2a

Discussion in 'The Projects Forum' started by xmen33, Aug 27, 2011.

  1. xmen33

    Thread Starter New Member

    Aug 27, 2011
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    Hi

    I went to design a 40V 2A power supply to run 3 stepper motor 3A.
    i used L298 to deal with motor, the max volt can drive is 50V with 2A " i get this from datasheet L298 is this right? ".

    so i went to design this power supply with regulator .
     
  2. SgtWookie

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    Jul 17, 2007
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    The L298 is outdated and inefficient. Internally, it uses Darlington pairs both as saturated switches and emitter followers. At 2A current, you will drop around 4v-4.5v across the L298 itself, and so it will dissipate a lot of power as heat. Unless you have a very large heat sink on the L298, you will burn it up.

    You usually don't need a regulated supply when using a chopper driver.
     
  3. xmen33

    Thread Starter New Member

    Aug 27, 2011
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    what should i do about power supply.

    example: i design a 40v 5a power supply and connect it with 3 L298 and 3 stepper , if one of this stepper run only so the current will be 4 - 5A and will burn the L298 and the stepper .
    is this right?
     
  4. SgtWookie

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    The L298 needs to be used with the L297. The L298 is the power Darlington portion, the L297 is the chopper driver portion.

    The L297 monitors the current flowing through the sense resistors, and switches the H-bridge on and off to keep the average current flow at a preset value.
     
  5. xmen33

    Thread Starter New Member

    Aug 27, 2011
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    i will use pic with L298.
    so i think that 40v with 10 a is ok.

    can u help me with design this power supply , i know that i need transformer , bridge , some cap and regulator .
     
  6. SgtWookie

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    Do you understand how a chopper driver works?

    If not, you better read through the datasheet and whatever application notes that you can find for the L297/L298 before you start writing programs.

    If you "forget" to monitor the current across your sense resistors at any point in time, you will fry your L298 in nothing flat.

    You keep saying regulated. You really don't need regulated. You could build an unregulated supply that output perhaps 36v, and just let the chopper drive take care of the rest.

    If you obtained a transformer with a secondary rated for ~24vac @ 6A-10A, that would likely do it. If you are in a place that has poorly regulated mains power, you should state that.
     
  7. xmen33

    Thread Starter New Member

    Aug 27, 2011
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    i read about L298 and design circuit with Proteus.

    1) power supply circuit:
    [​IMG]

    2) pic with L298 circuit:
    [​IMG]

    are there any mistake in this circuits?
     
  8. SgtWookie

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    Jul 17, 2007
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    It's obvious that you do not understand how the L297 controls the L298.

    Here is a datasheet for the L297:
    http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000063.pdf
    The basic connection schematic for the L297/L298 is on page 1.
    The logic functional diagram is on page 2.
    The pin functions are on pages 3-4.
    The functional description begins on page 4.

    You will need to programmatically duplicate the functions of the L297 in the PIC. If you don't do that, you will fry the L298 or your stepper motors.

    In order for you to duplicate the functionality of the L297 in the PIC, you must first understand how the L297 works.

    Read the documentation.
     
  9. xmen33

    Thread Starter New Member

    Aug 27, 2011
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    I use the pic to send

    there are 3 way to control the 6 wire stepper " torch only , speed, torch with speed " .
    in the bast , i run the stepper with uln2003 but this ic deal with small volt and ampere .
    if there are problem in pic circuit tell me to fix it , what about the other circuit ?
     
  10. SgtWookie

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    The L298 is a dual H-bridge driver that can be used for either bipolar stepper motors, or two DC motors that you may wish to drive in both forward and reverse directions.

    The ULN2003 can be used to drive unipolar motors, but not bipolar motors. So, you must have unipolar motors then? Five or six wires?

    Do you have a manufacturer part number and data sheet for your stepper motor(s)?

    I don't want to have another 10 exchanges without having that information in front of me.
     
  11. xmen33

    Thread Starter New Member

    Aug 27, 2011
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    yes i have unipolar 6 wire call " sanyo denki 103h6707 "
     
  12. SgtWookie

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    Do you have a datasheet for these motors?

    It's taking me too long to find them.
    I don't think you provided the entire part number.
     
  13. xmen33

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    Aug 27, 2011
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  14. SgtWookie

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    Well OK, but that datasheet does not cover your particular model as far as the voltage rating.

    Can you measure the windings using an ohmmeter to determine the DC resistance, and post what you measure?
     
  15. xmen33

    Thread Starter New Member

    Aug 27, 2011
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    it 2.3 -> 2.4 ohm
     
  16. SgtWookie

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    OK, so 3A @ 2.3 Ohms; about 6.9V would be the normal operating voltage. 4x or 5x would probably be a decent target operating voltage; roughly 27.6v to 34.5v.

    If you were going to run those motors in bipolar mode, you would need twice the supply voltage.

    If you're going to use full step or half step, you will need ~6A per motor; 3A per phase that will be active.

    Full step:
    0011
    0110
    1100
    1001
    0011
    ...etc

    Half step:
    0011
    0010
    0110
    0100
    1100
    1000
    1001
    0001
    0011
    ...etc

    You would be better off to use some logic-level N-ch power MOSFETs and gate drivers for them.

    You also need some method to control the current. You may be better off to have a dedicated chopper driver circuit; if you ever forget about controlling your motor current, you will burn something up very quickly.
     
  17. xmen33

    Thread Starter New Member

    Aug 27, 2011
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    sorry if i Bother you .
    what is better bipolar mode or unbipolar mode, because i went speed and torch.
    and what the best ic to do that? " i will use pic to send step ... "
    edit:
    i use pic in my project to receive data from serial port and make some operation with it, so the pic will have alot of pin dont use so i went to use it ...
     
  18. SgtWookie

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  19. SgtWookie

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    You're not bothering me. If I sound irritated, I apologize; I have several things going on both on the board and where I am.

    Bipolar is harder to understand than unipolar. Have a read through that Application Note I linked to if my last reply.
    Running your unipolar steppers as bipolar steppers means that you'll need twice the voltage to get the same speed/torque as you would in unipolar mode. That's because instead of operating your coils independently (center tapped), you would ignore the center tap; so the windings would have twice the inductance. The higher the inductance, the longer it takes to get current flow to its' desired level. Low current flow= low torque at speed, thus lower top speed.

    It depends on a number of things. Have you looked over at CNCzone.com? Lots of folks on there using various software packages, might even be some that have your motors.

    Hmm - have you looked at Roman Blacks' LiniStepper project?
    Google that name.

    Roman Black has some very interesting things about stepper motors and their control on his site.
    http://www.romanblack.com
     
  20. xmen33

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    Aug 27, 2011
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