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View Full Version : Does a 15 Khz 3-phase magic sine wave generator with parallax possible ?



sriliam
09-20-2011, 03:57 PM
Hi,

All is in question : is it realistic to make a magic sine wave generator up to 15 Khz with multi-core parallax microcontroller.

Ordinary PWM from 4 Mhz in give 60 hz out with magic sine wave technics from its own site (http://www.tinaja.com/magsn01.asp) doc.

Does someone worked on this ? Please let me know if so.
Best reagards.
Sril

Tracy Allen
09-21-2011, 08:11 PM
Here are a couple of threads... This is for single phase, but it has the gist of it. A couple of people have asked about 3-phase, but I can't find the threads. I wrote the code just out of curiosity and because the Prop is well suited to the tight timing.
Duty-mode-output-to-drive-Power-MosFET (http://forums.parallax.com/showthread.php?92255-Duty-mode-output-to-drive-Power-MosFET)
magic-sinewaves (http://forums.parallax.com/showthread.php?92317-magic-sinewaves)

The funny thing is, I don't think I have ever seen a definitive, successful application of magic sine waves to motor control or anything else. Not so much as a link on Don Lancaster's site. Does anyone know of one?

tdlivings
09-21-2011, 10:04 PM
Here is a link to Don's site
http://www.tinaja.com/

sriliam
10-22-2011, 12:51 PM
Many thanks for replies.
For hz range : no problem, there is many docs.
For Khz range : nothing about this with magic sinewaves. I wrote to lancaster and he reply me that's was _not_ possible at this frequency range.
So, I was wondering if it could be done by using threads facilities of parallax.
Best regards.

PJ Allen
10-22-2011, 02:11 PM
"realistic" : "magic sinewaves"?
What're "magic sinewaves"?

pjv
10-22-2011, 04:18 PM
PJ Allen:

Follow the links above to find Don Lancaster's explanation of the concept. In essence, it is a method of generating power drive pulses with width and spacing properties such that the harmonics created by one pulse are cancelled by the harmonics of following pulses.

Very clever, but I've never tried it.... hope to someday soon to see if it is ppossible to drive a high speed 3 phase BLDC motor this way.

Cheers,

Peter (pjv)

PJ Allen
10-22-2011, 05:27 PM
"magic" : Don Lancaster
I'm speechless.

ctwardell
10-22-2011, 05:30 PM
I guess the first thing you will need is a Postscript interpreter for the Prop... ;-)

C.W.