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From: "Frank Bemelman"
References: <email@example.com> <firstname.lastname@example.org> <3DA05D28.CC5530C1@webaccess.net>
Subject: Re: steppermotor as encoder -> presto, moterized pot.
Date: Sun, 6 Oct 2002 19:20:02 +0200
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
Organization: EuroNet Internet
NNTP-Posting-Date: 06 Oct 2002 17:20:10 GMT
"Chuck Simmons" schreef in bericht
> Frank sent me an email that I answered. At least part of my thinking
> that went into the answer might be appropriate here. Frank's idea boils
> down to using the BEMF from the stepper to sense motion whether by the
> motor or by turning the knob. Since steppers usually have enormous
> torque constants compared to spindle motors, this idea has considerable
> merit. I could come up with a long list of problems but I think that
> they all could be solved in the application without much cost. It takes
> thinking it through and experimenting a bit.
> I could take this on. I would use an AVR because I can usually wangle a
> free AT90S8515 and the lowest grade seems to run at 10MHz (the specs say
> it won't but I do it anyway). Thus the processor power is through the
> roof for this application. It looks like a fun project however futile.
I sent my reply as an email by accident. Here's my reply again, with
> That last characteristic would perhaps be an advantage, volumeknobs often
> have these detents on purpose. During the moments the stepper needs to
> works as an encoder, I intended it to be disconnected from the drivers,
> and use the coils as pickups. I measured a small stepper motor here,
> and when giving it nice turns, it generates rather nice pulses. When
> it slow, it all looks a bit shabby. Not to worry about, after all it
> was just an idea, intended to be carried out by others ;)
Not a bad idea. If people want to learn how to control anything, they
need to learn to use the components. In your suggestion, you are
proposing using the BEMF of the stepper. I haven't seen that done
(though it is done with brushless DC motors) but since most steppers
have high torque constants, it should work pretty well. It's a nice idea
that just requires a little immagination and experimentation to fill in
the details. BTW, I can get clean BEMF from a brushless DC motor PWM
driven from about 100RPM up. Talk about ragged coil voltage! This says
your stepper having at least 10 times the torque constant has a lot of
potential for very low speed application like a volume control.
To get a 100% tight interpretation of the stepper used as an encoder
might be difficult, but to make it serve as a volume control, it may
give enough satisfaction. Now we only need a volunteer that examines
this. I don't have the authority to call in Tony, perhaps Will can
pick this up.
Hahaha, I love you guys picking up on silly ideas ;) Martin can
do the analog stuff, the real volume controlling bit...
(remove 'x' & .invalid when sending email)
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