Help with DC motor driver circuit

Discussion in 'The Projects Forum' started by herher, Oct 18, 2011.

  1. herher

    Thread Starter Member

    Oct 18, 2011
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    Hi all the experts here,

    I would like to ask if there is any motor driver or motor driver circuit that can receive +-10V (+10V to -10V) analogue voltage and is able to produce relevant voltage with current amplified?? The signal I stated above is the normal voltage signal, not the PWM signal.

    Please advice, your kind assistance will be much appreciated. Hope to hear from you all soon. Thanks. :)

    Best Regards,
    herher
     
  2. JDT

    Well-Known Member

    Feb 12, 2009
    658
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    There certainly is. How you do it depends on how much current the motor needs.

    For low currents it could be done completely analog. Op-amp, for example.
    For more current, a Pulse Width Modulated "H" bridge would be used.
     
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    ?, is motor reversable?
     
  4. herher

    Thread Starter Member

    Oct 18, 2011
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    Hi, thank you very much for the reply.

    Actually the +-10V signal to the motor driver is generated from a target processor, I call it "microbox". I would like to ask is it possible to rotate the motor in different direction (CW & CCW) by supplying positive voltage and negative voltage respectively (e.g: positive signal to rotate clockwise and negative signal to rotate counterclockwise) without inverting the connection to the DC motor terminal. Because usually if we wanted to reverse the motor rotating direction, we will invert the connection to the dc motor terminal.

    The signal generated from the microbox is a PID controlled loop signal, so there will be positive signal and negative signal. Is there any motor driver circuit or motor driver which can handle these specification? Please advice. Please let me know if the explaination is unclear. Thank you very much. :D

    Best Regards,
    herher
     
  5. #12

    Expert

    Nov 30, 2010
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    6,757
    If the motor will run backwards when the voltage is reversed, this will work. If you tell how much current the motor requires, we can figure out HOW it will work.
     
  6. herher

    Thread Starter Member

    Oct 18, 2011
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    Hi,

    Thanks for the reply. The rated current of the motor is 410mA, but the motor is going to be used to carry some load so I think the best option is motor driver circuit that can draw 2A current or above.

    Please advice. Thank you very much. :)

    Best Regards,
    herher
     
  7. #12

    Expert

    Nov 30, 2010
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    This chip will do it, but it's expensive and this job could probably be done cheaper if we had more information about your skill level and your motors needs.
     
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Here is an outline of a possible interface from input to an H bridge. Logic supply +10 to +12V, ICs are comparotors.
     
  9. herher

    Thread Starter Member

    Oct 18, 2011
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    0
    Hi,

    Thank you very much for the replies and the sources.

    I have tried to read the opa544 datasheet but I wonder whether this chip is suitable for my application.

    From the chip specification, the input voltage for +Vin pin is positive voltage (e.g: +6V) and the input voltage for -Vin pin is negative voltage (e.g: -6V), but the signal that generated from my "microbox" can only produce either positive voltage or negative voltage (that means the +Vin can only receive either positive or negative signal while the -Vin is connected to the ground pin of the microbox). So is this chip still applicable for my project?

    Besides, the analogue +-10V (+10V, +9V......0V.......-9V, -10V) I mean is input signal to the driver not the supply voltage. Sorry if my explaination is unclear.

    Please advice. Hope to hear from you soon. Thanks. :)

    Best Regards,
    herher
     
    Last edited: Oct 24, 2011
  10. ifixit

    Distinguished Member

    Nov 20, 2008
    638
    108
    Hi herher,

    You can use the OPA544 as a power buffer. Your ±10V (low current) signal will not be amplified in voltage, but will have the power boosted to more than 2 Amps if the motor load demands it.

    I think this is what you want... correct? A conceptual circuit diagram is attached to show a times 1 buffer amplifier. ±10V in, ±10V out with much more power available.

    Since you don't want PWM, power disipation in the OPA544 will be high when motor is at full load and higher still under a locked-rotor condition. Mount the OPA544 on a good heatsink and supply forced air cooling if required to keep the case temperature low enough to get 2A you required.

    Quote from the spec...
    The OPA544 has an internal current limit set for approxi-
    mately 4A. This current limit decreases with increasing
    junction temperature as shown in the typical curve, Current
    Limit vs Temperature. This, in combination with the thermal
    shutdown circuit, provides protection from many types of
    overload. It may not, however, protect for short-circuit to
    ground, depending on the power supply voltage, ambient
    temperature, heat sink and signal conditions

    Depending on your application, this device may not be dependable enough under worst case situations.

    Regards,
    Ifixit
     
  11. herher

    Thread Starter Member

    Oct 18, 2011
    53
    0
    Hi,

    Thanks for the reply.

    Ya, you are right, this is what I want. Besides, can I know the range of the input signal? So, despite how much voltage is supplied to the input pin, the output pin will still generate identical signal as input but with higher current right (1V output 1V, -1V output -1V and so on)?

    Apart from this, I have a doubt over here...what is the difference actually between supplying positive voltage and negative voltage to the dc motor. Will the motor rotating direction be inverted as what I expect (I have never try this before, because usually if I want to rotate motor direction I will invert the connection to the motor terminal)?

    I will try to use this chip first, and by the way is there any other alternative chip (just want to compare)?

    Please advice. Hope to hear from you soon. Thank you very much. :)

    Best Regards,
    herher
     
  12. ifixit

    Distinguished Member

    Nov 20, 2008
    638
    108
    Correct. However the range of the input is limited to approximately 5 Volts less than the power rails. My example uses ±15V rails so the output will safely go to ±10V. If you tried to drive the input with ±15V, the output would not follow but would limit itself to something less depending on the current and temperature.

    Both methods have the effect of reversing the current through the motor. Since you have a ± supply it easier to change the polarity to the motor than to reverse the connections to the motor.

    The LM675 from National Semiconductor is an older version the the OPA544. It has lots of history so there are good application notes you can refer to when using this kind of part.
    Here is a link to power amp modules. More money, but less design work. I looked at the site briefly and they look like a solution for your application.
    http://www.powerampdesign.net/poweropamps/railtorailmodels.html

    Regards,
    Ifixit
     
  13. herher

    Thread Starter Member

    Oct 18, 2011
    53
    0
    Hi,

    thanks for the reply.

    I am not going to use the power amplifier model that you have shown me because I have to build my own circuit with the Op-amp. By the way, still thanks a lot for the information.

    Anyway, I still have some questions here regarding to the power supply of the chip. In order to enable +-signal, the chip must be supplied with dual power supply (+15V and -15V). I have read the op-amp article in your site, http://www.allaboutcircuits.com/vol_3/chpt_8/2.html, can I apply the dual power supply connection that shown in the third image?

    Besides, in fact I am going to use two dc motor for my project instead of one. Thus, is there any counterpart of OPA544 which can handle two dc motors?

    If there is no such chip then I will have to use two OPA544. But is it possible to satisfy the power demand of two opa544 by just using a +-15V regulated power supply?

    Please advice. Thank you very much.

    Best Regards,
    herher
     
  14. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
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    If you have +&-V supplies capable of powering two motors in parallel[?],then a 1/2 H bridge could be used, ss a P-ch FET & N-ch FET. What is motor operating voltage?
     
  15. ifixit

    Distinguished Member

    Nov 20, 2008
    638
    108
    Hi Herher,

    Yes.

    Use two OPA544 opamps, one for each motor

    Yes. Use a power supply that can supply enough power for at least two motors. If each motor could use up to 2 Amps each, then use a dual output regulated power supply (±15V) that can supply 5 Amps. A little extra doesn't hurt. It would be best if the current could can be set to limit at 4 Amps. This would help to protect the motors and the OPA544s from damage if there is a fault which causes the motors to stall with too much load.

    Regards,
    Ifixit
     
  16. herher

    Thread Starter Member

    Oct 18, 2011
    53
    0
    Hi,

    Thanks for the replies.

    Bernard, I am going to use two signals generated from the microbox to control two dc motors respectively. The motor operating voltage is 12V.

    Ifixit, the attached file is the image of the regulated power supply that I am going to use. It provides three output ports: +5V/10A, +15V/3.5A and -15V/1.0A. The output current of the +-15V supplies are different so I wonder if this supply could be used for powering up the OPA544? Besides, does the +15V and -15V power supplies in the dual power supply circuit (that I have shown you in the previous reply) share the same common?

    Please advice. Thank you very much. :)

    Best Regards,
    herher
     
    Last edited: Oct 29, 2011
  17. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    The -15 supply is insuficient to operate the OP Amp or 1/2 H; +15 just marginal for full H bridge.'might be time to measure motor current at expected load.
     
    Last edited: Oct 30, 2011
  18. herher

    Thread Starter Member

    Oct 18, 2011
    53
    0
    Hi,

    thanks for the reply.

    I have another question here. Actuallly, besides using the +-15V power supply to power up the two opa544, I still need another two +0 to +10V analogue signal (used with potentiometer) to used as measuring signal to return back to the microbox.

    So, in short I need +-15V to power up two OPA544 and +10V for two potentiometer which are used as voltage divider. Thus, I would like to request for some suggestions on how to handle these power supplies efficiently.

    Please advice, thank you very much. :)

    Best Regards,
    herher
     
  19. ifixit

    Distinguished Member

    Nov 20, 2008
    638
    108
    Hi Herher,

    So long as the signal has very little load on it from the microbox input then you can use a voltage divider from the +15V supply you allready have. See diagram. Change the resistors to suit the value of pot you have if required.

    Good Luck,
    Ifixit
     
  20. herher

    Thread Starter Member

    Oct 18, 2011
    53
    0
    Hi,

    Thanks again for the reply.

    "So long as the signal has very little load on it from the microbox input then you can use a voltage divider from the +15V supply you allready have."
    Sorry, I don't really understand this, doesn't it the more important thing is the amount of power/current that the microbox can sustain from the signal generated from the voltage divider?

    So you mean I can use the +15V produced from a regulated power supply to power up 2 OPA 544 and and supply voltage to 2 voltage divider simultaneously? Actually I got think of that before but I am not sure the maximum input current or power that the microbox can sustain. Apart form this, I wonder the power supply has sufficient power to supply all these. So, what is the output current should the power supply have in order to fulfill all the demands?

    I just want to consider and confirm everything before purchasing anything. Please advice. Thank you very much. :)

    Best Regards,
    herher
     
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