Tim Wescott wrote:> Jerry Avins wrote: > >> Richard Owlett wrote: >> >>> Jerry Avins wrote: >>> >>>> knheman206 wrote: >>>> >>>>> help!i need to program a DSPTMS320LFA) using C for a bRUSHLESS DC >>>>> motor. [snip] >>>> >>>> >>>> >>>> >>>> DSP or not DSP, do you know enough about brushless motors to write a >>>> description of how to drive one? You'll more likely succeed if you do. >>>> >>> >>> Never having heard of a "brushless _DC_ motor", I went to Google. >>> The descriptions reminded me of stepper motors. >>> >>> Is there an intrinsic difference? >>> How did "DC" end up in the name? >> >> >> >> It's exactly like a stepper except for causes the steps. In a stepper, >> steps are commanded by a controller that sets the rate. In a brushless >> DC motor, the steps are determined by the rotor position, usually >> sensed by Hall-effect devices. Another way to look at that structure >> is as a permanent-magnet motor with an electronic, not a brush, >> commutator. It's a motor. It runs off DC*. What would you call it? >> > I would call it a permanent-magnet synchronous motor -- but the world > calls them "brushless DC" so that's what I call them."Permanent-magnet synchronous motor" applies equally to steppers. "Synchronous motor" implies AC. ("Slo-Syn" s originally applies to a low-speed synchronous motor: 72 RPM at 60 Hz that, with a simple change of winding impedance, happens to make a dandy stepper.) Were I to search for a better name, I would probably settle on "solid-state-commutated motor" Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Using C to program DSP TMS320LF2407A
Started by ●February 25, 2005
Reply by ●February 26, 20052005-02-26
Reply by ●February 26, 20052005-02-26
Jerry Avins wrote:> Tim Wescott wrote: > >> Jerry Avins wrote: >> >>> Richard Owlett wrote: >>> >>>> Jerry Avins wrote: >>>> >>>>> knheman206 wrote: >>>>> >>>>>> help!i need to program a DSPTMS320LFA) using C for a bRUSHLESS DC >>>>>> motor. [snip] >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> DSP or not DSP, do you know enough about brushless motors to write >>>>> a description of how to drive one? You'll more likely succeed if >>>>> you do. >>>>> >>>> >>>> Never having heard of a "brushless _DC_ motor", I went to Google. >>>> The descriptions reminded me of stepper motors. >>>> >>>> Is there an intrinsic difference? >>>> How did "DC" end up in the name? >>> >>> >>> >>> >>> It's exactly like a stepper except for causes the steps. In a >>> stepper, steps are commanded by a controller that sets the rate. In a >>> brushless DC motor, the steps are determined by the rotor position, >>> usually sensed by Hall-effect devices. Another way to look at that >>> structure is as a permanent-magnet motor with an electronic, not a >>> brush, commutator. It's a motor. It runs off DC*. What would you call >>> it? >>> >> I would call it a permanent-magnet synchronous motor -- but the world >> calls them "brushless DC" so that's what I call them. > > > "Permanent-magnet synchronous motor" applies equally to steppers. > "Synchronous motor" implies AC. ("Slo-Syn" s originally applies to a > low-speed synchronous motor: 72 RPM at 60 Hz that, with a simple change > of winding impedance, happens to make a dandy stepper.) Were I to search > for a better name, I would probably settle on "solid-state-commutated > motor" > > Jerryto-mah-to, to-may-to -- the motor itself sees AC, so implying it isn't a bad thing. The two big differences between steppers and brushless motors is that in a stepper cogging is a good thing vs. brushless motors where it's undesirable, and steppers are generally designed with enough winding resistance to happily withstand being energized without moving where your average high-performance brushless would be dripping copper if you gave it rated voltage in stall. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●February 26, 20052005-02-26
Tim Wescott wrote: ...> to-mah-to, to-may-to -- the motor itself sees AC, so implying it isn't a > bad thing.Always. But the fan on your CPU connects to a DC power supply with the two wires coming out of it, and a commutator-and-brush motor's armature coils also see AC.> The two big differences between steppers and brushless motors is that in > a stepper cogging is a good thing vs. brushless motors where it's > undesirable, and steppers are generally designed with enough winding > resistance to happily withstand being energized without moving where > your average high-performance brushless would be dripping copper if you > gave it rated voltage in stall.That's simple: just change the rating! Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●February 27, 20052005-02-27
Jerry Avins wrote:> That's simple: just change the rating!For a state-of-the-art example, see here: http://www.tip.csiro.au/Machines/success/sc.html It's >98% efficiency, and they've even got a thermal model so Jerry can work out how to change the rating :) A downside of this type of motor (ironless) is the really low inductance, which makes the power electronics difficult. -- James Kennedy Electronics Design Engineer Tritium Pty Ltd Brisbane, Australia
Reply by ●February 28, 20052005-02-28
James Kennedy wrote:> Jerry Avins wrote: > >> That's simple: just change the rating! > > > For a state-of-the-art example, see here: > http://www.tip.csiro.au/Machines/success/sc.html > > It's >98% efficiency, and they've even got a thermal model so Jerry can > work out how to change the rating :) A downside of this type of motor > (ironless) is the really low inductance, which makes the power > electronics difficult.The shape of the design is reminiscent of printed servo motors of 20 or 30 years ago. (No surprise. Does PMI still exist) Google shows no "Printed Motors Inc", but there is "PML FlightLink Ltd (Formerly Printed Motors Ltd)". Oh, well! Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●February 28, 20052005-02-28
Jerry Avins wrote:> The shape of the design is reminiscent of printed servo motors of 20 or > 30 years ago. (No surprise. Does PMI still exist) Google shows no > "Printed Motors Inc", but there is "PML FlightLink Ltd (Formerly Printed > Motors Ltd)". Oh, well!Yes, it's possible to make these motors with standard PCB techniques (usually, multiple boards stacked togther) but the copper density just isn't enough for the higher performance designs. They're good for 'cheap' though. FYI, the CSIRO motor I linked to is *not* cheap, and sold for around $10k or so - but that price seems to be acceptable for solar cars... Even more OT, it's interesting to note that one of those motors (1.8kW i.e. toaster power levels) is enough to run a solar car at well over 100km/h (65mph). -- James Kennedy Electronics Design Engineer Tritium Pty Ltd Brisbane, Australia
Reply by ●February 28, 20052005-02-28
James Kennedy wrote:> Jerry Avins wrote: > >> The shape of the design is reminiscent of printed servo motors of 20 >> or 30 years ago. (No surprise. Does PMI still exist) Google shows no >> "Printed Motors Inc", but there is "PML FlightLink Ltd (Formerly >> Printed Motors Ltd)". Oh, well! > > > Yes, it's possible to make these motors with standard PCB techniques > (usually, multiple boards stacked togther) but the copper density just > isn't enough for the higher performance designs. They're good for > 'cheap' though. > > FYI, the CSIRO motor I linked to is *not* cheap, and sold for around > $10k or so - but that price seems to be acceptable for solar cars... > > Even more OT, it's interesting to note that one of those motors (1.8kW > i.e. toaster power levels) is enough to run a solar car at well over > 100km/h (65mph).Most cars have much more power than they need, anyway. When starting, I can throw so much weight to the rear that my front-wheel-drive breaks traction on dry pavement. With 110 hp*, that was hard to to. With 135, I have to be careful not to. Even so, my station wagon gets to 60 mph* from a standing start in 11 seconds with 4 passengers and 100 lbs of tools. Ads for cars with double that horsepower and more leave me wondering who's nuts. On the road, most of those overpowered vanity buggies end up in my way. Jerry ______________________________________ * Lower case! -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●March 19, 20052005-03-19
The good stuff I miss by not being a regular participant... I feel lucky I caught this thread: On Sun, 27 Feb 2005 23:36:30 -0500, Jerry Avins <jya@ieee.org> wrote:>James Kennedy wrote:>> For a state-of-the-art example, see here: >> http://www.tip.csiro.au/Machines/success/sc.html >> >> It's >98% efficiency, and they've even got a thermal model so Jerry can >> work out how to change the rating :) A downside of this type of motor >> (ironless) is the really low inductance, which makes the power >> electronics difficult. > >The shape of the design is reminiscent of printed servo motors of 20 or >30 years ago. (No surprise. Does PMI still exist) Google shows no >"Printed Motors Inc", but there is "PML FlightLink Ltd (Formerly Printed >Motors Ltd)". Oh, well!The "printed motors" concept sounds familiar. A few months back I saw this Slashdot story: http://science.slashdot.org/article.pl?sid=04/11/25/1331227 which points to this story of a "Microgenerator:" http://www.gatech.edu/news-room/release.php?id=490 If you click on the pic links, specifically the one labeled "300 dpi JPG = 1.42 MB", you get a pic of these things, about one-inch diameter PCB patterns of three-phase "windings" with six pads for connections. This is activated by a spinning magnet over the traces, and the magnet will allegedly be driven by a tiny turbine being developed at another university, and the whole thing will allegedly power laptops and cellphones of the future. While I'm posting vaguely-related things, here's another webpage I recently stumbled across: http://www.otherpower.com/17page1.html>Jerry----- http://mindspring.com/~benbradley
