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[DPRG] Re: DPRGlist Digest, Vol 54, Issue 14

Subject: [DPRG] Re: DPRGlist Digest, Vol 54, Issue 14
From: Tawit iamtawit at gmail.com
Date: Thu Nov 20 14:01:00 CST 2008

Hi, I use 5KHz freq because this is the highest freq that my motor driver,
L298, can response.additionally, wit this 5KHz you will able to hear
high frequency noise from your motor so you know
that your robot (or your system) is about to run.

On Fri, Nov 21, 2008 at 5:00 AM, <dprglist-request at dprg.org> wrote:

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> Today's Topics:
>
>   1. PWM freq (Duane Brantley)
>   2. Re: PWM freq (Dean Hall)
>   3. Re: PWM freq (Mohit Taneja)
>   4. RE: PWM freq (Randy M. Dumse)
>   5. Re: PWM freq (Paul Burrell)
>   6. Anyone with a key gonna make it to the clubhouse early on
>      Sat? (DeltaGraph at aol.com)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 19 Nov 2008 10:10:40 -0800 (PST)
> From: Duane Brantley <d-brantley at sbcglobal.net>
> Subject: [DPRG] PWM freq
> To: Dallas Personal Robotics Group <dprglist at dprg.org>
> Message-ID: <342175.36545.qm at web82307.mail.mud.yahoo.com>
> Content-Type: text/plain; charset="us-ascii"
>
> If you use PWM to control the speed of your drive wheels, what PWM
> frequency are you using?    Why did you choose that frequency?
>
> Thanks,
> Duane
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> ------------------------------
>
> Message: 2
> Date: Wed, 19 Nov 2008 12:43:16 -0600
> From: Dean Hall <dwhall256 at gmail.com>
> Subject: Re: [DPRG] PWM freq
> To: dprglist at dprg.org
> Message-ID: <2AD90E78-DC54-4406-B2F3-77ACFC9691CE at gmail.com>
> Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
>
> I'm running PWM at just under 2 KHz.  I did not try to hit some exact
> magic number frequency, I just tried a few frequencies at different
> orders of magnitude and went with the one that seemed to perform.  I
> remember I avoided a higher frequency because the motor whine was
> annoying.  It still has whine, but it's not as annoying.  The Timer2
> peripheral in my ATmega103 running at 8 MHz determines the available
> frequencies.
>
>     /* Timer2 in non-inverted PWM mode, prescale by div 8 (1953 Hz) */
>     TCCR2 = (_BV(PWM2) | _BV(COM21) | _BV(CS01));
>
> The math works out like this: 8 MHz / 8 prescale / 2^9 for nine bit
> resolution == 1953.125 Hz
>
> !!Dean
>
> On Nov 19, 2008, at 12:10 , Duane Brantley wrote:
>
> > If you use PWM to control the speed of your drive wheels, what PWM
> > frequency are you using?    Why did you choose that frequency?
> >
> > Thanks,
> > Duane
> > _______________________________________________
> > DPRGlist mailing list
> > DPRGlist at dprg.org
> > http://list.dprg.org/mailman/listinfo/dprglist
>
>
>
> ------------------------------
>
> Message: 3
> Date: Wed, 19 Nov 2008 13:43:44 -0600
> From: "Mohit Taneja" <mohittaneja at gmail.com>
> Subject: Re: [DPRG] PWM freq
> To: dprglist at dprg.org
> Message-ID:
>        <42f969fd0811191143r412819a4w4c6532fe0961757d at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> I think it is a bad idea to use something around 15-20Khz because it will
> make a painful high pitch whine.
>
>
> Look up the data sheet on the motor controller you are using, it should
> list
> a typical PWM frequency.
>
>
>
> Mohit
>
> On Wed, Nov 19, 2008 at 12:43 PM, Dean Hall <dwhall256 at gmail.com> wrote:
>
> > I'm running PWM at just under 2 KHz.  I did not try to hit some exact
> magic
> > number frequency, I just tried a few frequencies at different orders of
> > magnitude and went with the one that seemed to perform.  I remember I
> > avoided a higher frequency because the motor whine was annoying.  It
> still
> > has whine, but it's not as annoying.  The Timer2 peripheral in my
> ATmega103
> > running at 8 MHz determines the available frequencies.
> >
> >    /* Timer2 in non-inverted PWM mode, prescale by div 8 (1953 Hz) */
> >    TCCR2 = (_BV(PWM2) | _BV(COM21) | _BV(CS01));
> >
> > The math works out like this: 8 MHz / 8 prescale / 2^9 for nine bit
> > resolution == 1953.125 Hz
> >
> > !!Dean
> >
> >
> > On Nov 19, 2008, at 12:10 , Duane Brantley wrote:
> >
> >  If you use PWM to control the speed of your drive wheels, what PWM
> >> frequency are you using?    Why did you choose that frequency?
> >>
> >> Thanks,
> >> Duane
> >> _______________________________________________
> >> DPRGlist mailing list
> >> DPRGlist at dprg.org
> >> http://list.dprg.org/mailman/listinfo/dprglist
> >>
> >
> > _______________________________________________
> > DPRGlist mailing list
> > DPRGlist at dprg.org
> > http://list.dprg.org/mailman/listinfo/dprglist
> >
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> ------------------------------
>
> Message: 4
> Date: Wed, 19 Nov 2008 13:52:47 -0600
> From: "Randy M. Dumse" <rmd at newmicros.com>
> Subject: RE: [DPRG] PWM freq
> To: "'Duane Brantley'" <d-brantley at sbcglobal.net>,      "'Dallas Personal
>        Robotics Group'" <dprglist at dprg.org>
> Message-ID: <15867EF82B0A48D286B678806423475C at RMDSONY3>
> Content-Type: text/plain; charset="us-ascii"
>
> I tend to prefer 20KHz, because it is just out of audio range.
> Some motors with lots of iron in them won't operate well at
> those rates, they have so much inductance, much less effective
> current passes through.
>
> On the other hand, the nicer coreless motors have almost no
> inductance. PWM rates of 40KHz or even 80KHz are appropriate for
> them, as lower rates turns into saturated cores and wasted heat.
>
> Randy
>
>
>  _____
>
> From: dprglist-bounces at dprg.org
> [mailto:dprglist-bounces at dprg.org] On Behalf Of Duane Brantley
> Sent: Wednesday, November 19, 2008 12:11 PM
> To: Dallas Personal Robotics Group
> Subject: [DPRG] PWM freq
>
>
> If you use PWM to control the speed of your drive wheels, what
> PWM frequency are you using?    Why did you choose that
> frequency?
>
> Thanks,
> Duane
>
>
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> ------------------------------
>
> Message: 5
> Date: Wed, 19 Nov 2008 12:27:51 -0800 (PST)
> From: Paul Burrell <peburrell at yahoo.com>
> Subject: Re: [DPRG] PWM freq
> To: rmd at newmicros.com, Duane Brantley <d-brantley at sbcglobal.net>,
>        Dallas Personal Robotics Group <dprglist at dprg.org>
> Message-ID: <603015.16954.qm at web30703.mail.mud.yahoo.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> But then there is the tradeoff of FET switching losses at higher
> frequencies.   You lose it somewhere or another.
>
> I prefer to run mine higher too (20KHz) and use good quality motors (Escap,
> Maxxon, etc).
>
> Paul
>
>
>
>
>
> ________________________________
> From: Randy M. Dumse <rmd at newmicros.com>
> To: Duane Brantley <d-brantley at sbcglobal.net>; Dallas Personal Robotics
> Group <dprglist at dprg.org>
> Sent: Wednesday, November 19, 2008 11:52:47 AM
> Subject: RE: [DPRG] PWM freq
>
>
> I tend to prefer 20KHz, because it is just out of audio range. Some motors
> with lots of iron in them won't operate well at those rates, they have so
> much inductance, much less effective current passes through.
>
> On the other hand, the nicer coreless motors have almost no inductance. PWM
> rates of 40KHz or even 80KHz are appropriate for them, as lower rates turns
> into saturated cores and wasted heat.
>
> Randy
>
>
> ________________________________
> From: dprglist-bounces at dprg.org [mailto:dprglist-bounces at dprg.org] On
> Behalf Of Duane Brantley
> Sent: Wednesday, November 19, 2008 12:11 PM
> To: Dallas Personal Robotics Group
> Subject: [DPRG] PWM freq
>
>
> If you use PWM to control the speed of your drive wheels, what PWM
> frequency are you using?    Why did you choose that frequency?
>
> Thanks,
> Duane
>
>
>
>
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> ------------------------------
>
> Message: 6
> Date: Thu, 20 Nov 2008 10:11:14 EST
> From: DeltaGraph at aol.com
> Subject: [DPRG] Anyone with a key gonna make it to the clubhouse early
>        on      Sat?
> To: dprglist at dprg.org
> Message-ID: <ca9.3b462e02.3656d812 at aol.com>
> Content-Type: text/plain; charset="us-ascii"
>
> Hey Folks,
>
> Anyone with a key going to be able to make it to clubhouse with a key
>  before
> me at about 11:00.
> Paul was asking so he could do some work with tankbot to get it running for
> the contest.
>
> Ron
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> End of DPRGlist Digest, Vol 54, Issue 14
> ****************************************
>



-- 
Tawit Uthaicharoenpong
iamtawit at gmail.com
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