I took apart a DVD-ROM drive for the heck of it and the control LSI is amazing stuff.
The driver chip has everything to directly drive all the mechanical parts in a CD-ROM drive from loading tray, focus, tracking, sled and the spindle motor. I find the spindle motor control the most fascinating.
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The chip controls the spindle motor using three phase PWM and reading the controller documentation leads me to believe the thing can be controlled somehow with pin 24.
The range is rather wide 230RPM while playing back audio CD at outer diameter and about 10,000RPM at 48x CAV mode. The chip can also apply reverse torque to quickly bring the disc to stop.
Is it difficult to make a variable speed drive using the spindle motor and the LSI pulled from a DVD-ROm drive to let me run the motor anywhere from 280 to 10,000RPM outside of the original drive? It would surely make a cool project part.
If this sophisticated control can be built into a $20 DVD-ROM drive, how expensive would it be to integrate a similar controller with beefier drive circuit to drive a motor in few hundred watt to a few kilowatt range?
You are in the 19th century.The germans have used this since 1990.The ICE train (InterCityExpress) has 13,000 HP, probably 8 traction motors and 2 "locomotives" (see
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if you can read german).The motors are asynchronous, three-phase squirrel cage and of course they must have sufficient torque to pull the train at stop and enough rpm to reach the maximum speed of 200 km/h.The cetenary system is 15 kV 16 2/3 Hz.Of course, there's such a drive as in the DVD.In normal electric locomotives there's a motor with brushes and excitation in series (like the one your drill has or your mixer, the one you make the ice-cream) and a transformer with 18 taps.To start the train, you need high current and low voltage.For maximum speed, you need high voltage and sufficient current.These motors are directly coupled on the wheels.
-- Dimitris Tzortzakakis,Iraklion Crete,Greece major in electrical engineering freelance electrician dimtzort AT otenet DOT gr ? "~Dude17~" ?????? ??? ?????? news: snipped-for-privacy@posting.google.com...
The major player in answering this question is "volume" Because the manufacturer can expect to sell millions of thses things,( DVD rom Drives) The development cost can be split, a few dollars over each item with no major impact in the overall price. After the development costs have been covered the manufacturer can then turn a reasonable profit before market saturation.
Not so with larger drives. The thing is there are a lot more "Players" in the motor drive market and in reality, if a maunfacturer goes to market with say a 2KW Drive there are probably more then 30 manufacturers out there each trying for their share of a rather limited market, so the prospective sales will be maybe only in the 1,000's and not the millions that the DVD rom makers have at their disposal.
another factor is PC users tend to have a rather "Geeky" approach to their equipment, with a fair market wanting the Latest and greatest, So they would be perfectily willing to throw away a perfectly good "Widgett" to replace it with another widgett of similar cost but more functions or better specifications. Usually in the industrial drive market, once a device is up and running, There it stays until it breaks or the whole machine is ready for an upgrade.
The other thing is the DVD Rom Drives are a dedicated application, Known Supply Voltage, Known load inertia, One job description. as we all know the application of Variable speed AC Drives has about as many diferent jobs and supply voltages as you immagination can put together. any reputable drive maker must design his drive to be as adaptible as possible so that it can be applied to any of these aapplications. This all adds Cost to the development.
Having said that, there, is no reason why the cost of drives will not fall as time progresses, as we learn how to do things more cost effectively and new technology either takes away some of the obsticales or makes them easier to contend with.
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