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Regen w/ motor mind B or HB-25 — Parallax Forums

Regen w/ motor mind B or HB-25

cabracercabracer Posts: 11
edited 2009-09-19 22:25 in BASIC Stamp
Hi all
does anyone know if you can perform regen using either the motor mind B or the HB-25 and if so can you point me to some example projects or code for the BS2

otherwise can some one point me to a controller that i can perform regen with and exaple projects and/or code for regen

thanks
CAB

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2009-09-11 17:12
    Neither the Motor Mind B nor the HB-25 are designed for regenerative braking.
  • cabracercabracer Posts: 11
    edited 2009-09-11 17:15
    Thanks Mike
    any idea of a controller that is capable of regen?

    CAB·
  • dev/nulldev/null Posts: 381
    edited 2009-09-11 23:18
    You won't find standard solutions for this anywhere, you'll have to build it.

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    Don't worry. Be happy
  • cabracercabracer Posts: 11
    edited 2009-09-12 03:03
    Guys

    thanks for the responses

    i was looking and i found this thing

    http://www.robotpower.com/products/simple-h_info.html

    it says this in the user manual:

    If regenerative braking of an inductive load such as a motor is desired it can be accomplished
    as follows: when slowing or reversing direction supply a low duty cycle drive to the load until
    the load has stopped or has reached a low RPM, then apply a brake or coast stop signal to
    the unit. The low average applied voltage of the low duty-cycle drive will allow the inductance
    of the load to boost the voltage at the battery terminals above the supply voltage and flow
    current back into the battery. Unfortunately the current sensors will not read properly during
    regeneration so the regeneration current level cannot be measured. Do not attempt

    regeneration with a bench power supply only with a battery.





    what do you guys think ?

    thanks

    CAB

  • Mike GreenMike Green Posts: 23,101
    edited 2009-09-12 04:40
    It's garbage. As far as I can tell this controller uses an ordinary H-bridge which has no way to allow current to flow from the motor into the battery. Even the explanation given makes no sense. If you've got a low duty-cycle drive going on, that means that the motor is connected to the battery only briefly and, even if the motor could feed back into the battery, it would only be when the H-bridge is turned on which is only a short time in each cycle.
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2009-09-12 05:02
    As Mike says... It is braking, but it's not re-generative braking.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • TimmooreTimmoore Posts: 1,031
    edited 2009-09-12 05:10
    http://www.dimensionengineering.com/ say their motor controllers are regen.
  • W9GFOW9GFO Posts: 4,010
    edited 2009-09-12 05:15
    dev/null said...
    You won't find standard solutions for this anywhere, you'll have to build it.

    This one claims to be regenerative.

    Sabertooth dual 25A regenerative motor driver.

    attachment.php?attachmentid=63712

    Rich H

    edit; Yeah, what Tim said, this is the same one.

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    The Servo Boss, a 12 channel servo tester kit from Gadget Gangster.

    Post Edited (W9GFO) : 9/12/2009 5:20:17 AM GMT
    Sabertooth.png
    485 x 390 - 226K
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2009-09-12 05:42
    To get honest regeneration you must have some sort of power conversion that will take the voltage produced by a motor (acting as a generator in fly-wheel mode) which is ALWAYS less than the supply voltage unless your going down hill and raise the voltage level so that it can provide an adequate charge voltage to the battery... Any power that your pulsing the coils (of the motor) with to get a back EMF kick above the supply voltage doesn't cut it if you’re claiming to recharge the battery due to energy conservation laws. If there is no voltage conversion, than at best you only have dynamic braking ... no regeneration.

    Note: at the cost of raising the generated voltage to a charge level above the battery supply, you sacrifice current. This means that most of your charging is done in bursts or "pulse charging".

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • cabracercabracer Posts: 11
    edited 2009-09-12 20:55
    wow that sabertooth seems legit

    what do you guys think of it?

    does anyone have a link to some information on philosophy and integration of regen

    or even generators in general so i can get a better idea of what i am up against

    thanks again for all the responses

    CAB
  • Mike GreenMike Green Posts: 23,101
    edited 2009-09-12 21:07
    The sabertooth documentation claims that it does regeneration, but there's not enough information in the documentation to judge. Note that a "proper" regeneration controller also has to have a charging controller so that the battery doesn't get damaged if, for example, you start with a nearly charged battery and the robot runs downhill using the regenerative braking to keep the speed under control.

    For general questions about electronics, try the Wikipedia. Do a websearch for "wiki electrical generator" and "wiki regenerative brake".
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-09-12 21:59
    Beau,

    Couldn't you short the winding briefly, to build up the stored energy, then release it at a higher voltage through a diode back to the battery? This would be the same circuit topology as a boost converter.

    -Phil
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2009-09-12 22:59
    Phil Pilgrim,

    Yes, that's typically how it's done, but the power source is considered part of the inductor or motor coil.

    I don't have any reason to doubt that the sabertooth 'could' be doing that, I was just basically stating what really should be happening.

    The posted circuit is regen in it's most basic form (a boost converter). The duty cycle at which you apply the braking signal determines how quickly you are going to stop or slow down. The frequency of the duty cycle is part of a feedback loop that monitors the output voltage. This circuit basically gets the voltage up and over the battery supply voltage, but you still need additional circuitry to take that voltage and correctly charge the battery chemistry that you will be using.

    Note: If you have a motor controller that allows free-wheeling (motor free spin) , then a regen circuit 'could' be applied as an after thought to any motor controller that meets that criteria.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
    REGEN.JPG
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  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-09-13 00:25
    Beau,

    What is the purpose of the diode on the far righthand side of your schematic?

    -Phil
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2009-09-13 03:41
    Phil,

    "What is the purpose of the diode on the far righthand side of your schematic?" - Well it was intended for the mosfet protection, however... looks like the bridge is doing that at the cost of a diode drop. That should be sufficient. Even though by design, the mosfet transistor has a reverse biased diode, for this type of application I like to bootstrap it with an external diode.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • wkinnewkinne Posts: 6
    edited 2009-09-18 18:58
    Hi Beau,

    I am new to the board here, I just received my Viewport ULT + Prop Proto USB a couple of days ago and just fired it up. I have a Sabertooth 2X25 and hope to drive 4 wheel chair motors with two of them once I learn the basics. I would love a simple schematic of exactly how to wire my Sabortooth to the Propeller board, and just enough spin code (with tons of remarks) to turn the motors both ways at variable speeds. I have downloaded some of the objects for this from Parallax's website but it is still Greek to me. I am a hands on kinda guy and would learn fast with a little head start. I am building a very large Robot and am very excited about my new Propeller with its 8 cogs. I used to program in Turbo Pascal and went to Electronics school way too long ago, so I feel I have the basics. I just need a little jump start. If this request is way out of line for this board, just let me know and I will post a new thread begging for help;-P

    wkinne
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2009-09-19 19:07
    "I would love a simple schematic of exactly how to wire my Sabortooth to the Propeller board, and just enough spin code (with tons of remarks) to turn the motors both ways at variable speeds." - Since I don't have a Sabortooth, the only thing I could give you is what you or I would be able to obtain from the Sabortooth datasheets. I know this isn't much help, but it would be a learning curve for me as well.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • dev/nulldev/null Posts: 381
    edited 2009-09-19 22:25
    This controller is quite versatile, and can take analog input as well as TTL RS-232. If you want detailed control of the motors you need to use the serial protocol.

    The easy way is to generate a PWM (pulse width modulation) signal. I don't know Spin, but this should be a walk in the park. Go to the Prop forum to get help for this.
    The 0V connection goes to Prop ground, and you could also power the Prop from the 5V output.

    The PWM signal needs to be smoothed out, so you need an RC circuit on each of the outputs. This is explained in the documentation, with 10K and 0.1uF cap.
    The motor will move in one direction when the PWM signal's RMS value is below 2.5V and in the other when it's above. Keep frequency above 1000Hz.

    Another option is to use a digital potentiometer, but that's overkill compared to PWM.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Don't worry. Be happy
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