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multi-phase oscillator

Started by zachary vex, November 21, 2004, 04:31:18 AM

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The Tone God

#40
January 08, 2006, 11:14:32 PM
That is a variation on DSS although limited in waveform flexibility but thats another topic.

Quote from: gez on January 08, 2006, 03:16:35 PM
Any chance of giving me the code of one of these PICs that can do the PWM thing, so I can look at the datasheet and see what's in store? [/gulp]  :icon_biggrin:

I don't have any of my PIC code lying around and most of it is in C anyways. You have learned an important lesson. Treat the datasheet like the bible and that applies to any uC. Make sure you always have the most update to date version too. The datasheet should be explain the principal and operation behind PWM well. Also Google is a good source of info. ;) It sounds complicated but it is really simple once you go through it. Don't be intimidated.

Andrew

aankrom

#41
January 09, 2006, 12:00:47 AM
It's not really the same thing but you could make an analog shift register like they use in analog synths. You could run an LFO waveform of any shape you wanted and have more or less exact copies come out at a phase determined by how fast you clock it.

I made one of these but haven't tested it yet:

http://www.cgs.synth.net/modules/cgs34_asr.html

(Ken Stone's CatGirl Synth site is awesome - also look at the Synthacon filter - killer for guitar with an envelope follower...)

aa

gez

#42
January 09, 2006, 03:48:56 AM Last Edit: January 09, 2006, 04:16:10 AM by gez
Quote from: The Tone God on January 08, 2006, 11:14:32 PMI don't have any of my PIC code lying around and most of it is in C anyways. You have learned an important lesson. Treat the datasheet like the bible and that applies to any uC. Make sure you always have the most update to date version too. The datasheet should be explain the principal and operation behind PWM well. Also Google is a good source of info. ;) It sounds complicated but it is really simple once you go through it. Don't be intimidated.


Ah, I should have phrased that differently, my apologies.  I didn't mean the code to program the thing - I wouldn't ask for that, a it would be cheeky, b it takes the fun out of learning - I meant the name of a chip that does the PWM thing so I can find the data sheet for it, i.e. the PIC equivalent of TL072.

So, could you give me the name of one of these chips please (one that can do PWM)?  :icon_biggrin:  When I googled PIC and PWM I didn't get very far - well, nothing easily identifiable as the method mentioned - so just need to find a chip then I can start learning.
"They always say there's nothing new under the sun.  I think that that's a big copout..."  Wayne Shorter

gez

#43
January 09, 2006, 04:13:00 AM
Double post.
"They always say there's nothing new under the sun.  I think that that's a big copout..."  Wayne Shorter

gez

#45
January 09, 2006, 06:31:30 AM Last Edit: January 09, 2006, 06:39:03 AM by gez
Thanks for the links Ton, but it's a case of information overload I'm afraid, though I'm sure when I know a little more those links will be of use. :icon_smile:

I have a couple of books which cover the basics but there's nothing really about PWM.  I don't know enough about PICs to evaluate the merits of one device over another, so I'd really appreciate it if someone could just gently guide this noob to a single device that will work for the application I desire.  I'm quite happy to do the rest...no matter how long it takes to learn!

I prefer to ask here as you lot understand what I'm trying to do.

Anyone?
"They always say there's nothing new under the sun.  I think that that's a big copout..."  Wayne Shorter

The Tone God

#46
January 09, 2006, 02:39:33 PM
Quote from: gez on January 09, 2006, 03:48:56 AM
Ah, I should have phrased that differently, my apologies.  I didn't mean the code to program the thing - I wouldn't ask for that, a it would be cheeky, b it takes the fun out of learning - I meant the name of a chip that does the PWM thing so I can find the data sheet for it, i.e. the PIC equivalent of TL072.

So, could you give me the name of one of these chips please (one that can do PWM)?  :icon_biggrin:  When I googled PIC and PWM I didn't get very far - well, nothing easily identifiable as the method mentioned - so just need to find a chip then I can start learning.

Ah the next lesson is the vendor's site tries to be as helpful as possible with selecting/using their products:

http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=1031&mid=10&lang=en&pageId=74

Look under the "PWM channels" field. :)

I kind of have an aversion when people say "use a PIC" when they should really be saying "use a micro controller". Maybe ten years ago that would have been appropriate but with the progress of the other vendors in the uC market that thinking is old and busted.

I don't use PICs very often these days. I prefer Atmel AVRs. You might want to look at them instead of PIC. Very easy and cheap to get into. Great support too. MANY of the AVRs have PWM. It has almost become a standard feature on all the new uC.

Andrew

gez

#47
January 09, 2006, 02:59:04 PM Last Edit: January 09, 2006, 03:00:38 PM by gez
Quote from: The Tone God on January 09, 2006, 02:39:33 PMI don't use PICs very often these days. I prefer Atmel AVRs. You might want to look at them instead of PIC. Very easy and cheap to get into. Great support too. MANY of the AVRs have PWM. It has almost become a standard feature on all the new uC.

Perhaps PICs aren't the best choice, but they're probably a good intro (for me) into this murky world of programming!  Once I understand the big picture a little better I'll follow up on your advice, thank you. 

Thanks for the link.  Need to do some research/reading now!  :icon_biggrin:
"They always say there's nothing new under the sun.  I think that that's a big copout..."  Wayne Shorter

The Tone God

#48
January 09, 2006, 03:43:04 PM
Quote from: gez on January 09, 2006, 02:59:04 PM
Perhaps PICs aren't the best choice, but they're probably a good intro (for me) into this murky world of programming!  Once I understand the big picture a little better I'll follow up on your advice, thank you. 

Actually what I was hinting at is that AVRs might be better for a beginner/intro then PIC. The choice is yours of course. Enjoy and good luck. :)

Andrew

gez

#49
January 09, 2006, 05:41:02 PM
Quote from: The Tone God on January 09, 2006, 03:43:04 PM
Actually what I was hinting at is that AVRs might be better for a beginner/intro then PIC.

Ok, I'll bear this in mind.  Thank you for your time Andrew (and everyone else who posted), much appreciated.

QuoteEnjoy and good luck. :)

I'll need it!  :icon_lol:

"They always say there's nothing new under the sun.  I think that that's a big copout..."  Wayne Shorter

TELEFUNKON

#50
January 14, 2006, 05:56:58 AM
gez:
just got the latest "Elektor" in the mailbox:
3-phase PWM motor-control;
maybe tweakable?

Dolly Parton

#51
January 14, 2006, 06:51:44 AM
Thanks for the tipoff Mr Funk On. 

Is it microcontroller based or 'analogue'?  The reason I ask is I have to travel quite a way to pick up a copy these days (local supplier won't stock it any more - not enough nerds in my area!).  :icon_lol:

gez Dolly
gez Dolly

Dolly Parton

#53
January 14, 2006, 08:44:09 AM
I'll pick up a copy next week.  Failing that, I'll pay to download the latest edition (nifty feature).  Many thanks! 
gez Dolly

TELEFUNKON

#54
January 14, 2006, 01:10:53 PM
hold back: at 2nd glance, the motorcontrol is not so suited for you...
the sine generator doesn`t appear in my issue... (?)

sorry for bothering

TELEFUNKON

#55
April 13, 2006, 04:05:32 AM
Quote from: gez on January 08, 2006, 05:49:24 AM
Quote from: TELEFUNKON on January 08, 2006, 04:31:38 AM
IIRC, gez posted a 4phase triangle oscillator himself, a while ago?

Indeed I did Mr Funk-on, but I need a rectified sine in quadrature.

Just did a spell check and apparently I should be called fez...
just wondering here (while tinkering with a new idea, and drawing b**by curves),
whether the purpose for which you`re after it,
really actually asks for 90° separated >rectified sine waves<
(let me call them "hyperbolix" for the moment),
or if the fact that 180° separated "hyperbolix" represent
the same absolute amplitude-relationships like a sine/cosine pair
could fulfill your needs.
(e.g.: absolute max amplitude of the sine coincides with zero amplitude
of cosine, while sine @ zero means max absolute amplitude of the cosine).
You know what I mean!?
(Assuming here, that like me, you don`t need a zero-symmetrical
"hyperbolic" wave, but only positive values incl. 0).
The other question is: whatever is going to happen with the "hyperbolix"
( -  plz don`t tell me - I don`t wanna know - )
will an inverted version "sound"?


Finally: hasn`t this topic crossed the forums` border
to be filed under:
DIGITAL & DSP ?

gez

#56
April 13, 2006, 04:47:38 AM Last Edit: April 13, 2006, 05:18:02 AM by gez
Mr Funk-On!

The terminology I used is a bit confusing, I admit, because when you FWR sine waves in quadrature you end up with only two wave forms, the second starting halfway through the first's cycle; technically they're 180 degrees apart.  In order to get FWR sines in 'quadrature' (basically, what I want is four inverted 'hyperbolic' waveforms equally spaced) you actually need the four sine waves being rectified to be 45 degrees apart, not 90 degrees (if one were doing this in analogue using a 'ring/loop' phase shift oscillator that is).  Also, as you point out, when you invert a 'hyperbolic' you end up with a very different beast indeed, so 'direction' is important, i.e whether the rectified wave form is negative or positive going. 

No big secret here, I've mentioned a number of times (not that anyone seems to listen) that this type of wave form - the inversion of the 'hyper triangle' - sounds best (to my ears) with LFO swept filters.  With triangles and sines, too much time is spent in the 'deep end', especially with the latter wave form, so for a large part of the sweep things just sound muddy.  Although you can compensate by shifting the range of the sweep higher, you then loose some of the impact of the filter - less quack.  With the inverted hyperbolic,  you get a nice sharp attack, which gets you out of the mud quickly, and then it hangs around sweeping majestically through the mids and highs, before dropping briefly back into the mire.  In short, it sounds better. 

Why 'quadrature'?  If you sweep four filters in quadrature, all set up the same and in parallel, you get a pseudo-echo effect.  A lot of work and not worth doing for just this effect, but from the same LFO you can get 'anti-wah' and the straight forward sweep by itself, so you get three sweeps for the price of one.  I've figured out most of the PIC part (though haven't tried it yet), just got waylaid with MIDI now...
"They always say there's nothing new under the sun.  I think that that's a big copout..."  Wayne Shorter

TELEFUNKON

#57
April 13, 2006, 05:23:51 AM
Quote...you actually need the four sine waves being rectified to be 45 degrees apart

yes, you pointed me to my former misinterpretation in a PM a while ago  :icon_redface:

it was only my simplistic new thingy, (which in fact does only need the min/max relation of 2 hyperbolix 180° apart, plus their inverted pairs), that reminded me of this old thread,
and made me wonder again if the 90° hyperbolix  is really what you`re striving after...
:icon_wink:

Mr. ZVex: it seems you have an acrobat reader problem (old version?),
if you can`t view those .pdf files. They do work here.
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