[LAU] Wah update

Folderol folderol at ukfsn.org
Fri Aug 21 18:12:12 EDT 2009

On Thu, 20 Aug 2009 17:21:10 -0700
Ken Restivo <ken at restivo.org> wrote:

> On Fri, Aug 14, 2009 at 10:19:25PM +0100, Folderol wrote:
> > On Fri, 14 Aug 2009 22:43:15 +0200
> > Arnold Krille <arnold at arnoldarts.de> wrote:
> > 
> > > On Friday 14 August 2009 21:59:53 Ken Restivo wrote:
> > > > It sounds great. Now I'm either going to hack together an auto-wah via AMS
> > > > or something and an envelope follower, or build myself an Arduino pedal
> > > > footcontroller.
> > > 
> > > Get a footcontroller or control it from the keyboards modulation-wheel (if not 
> > > used otherwise). Auto-Wah sounds crap.
> > > 
> > > Arnold
> > 
> > Nonono
> > Building an Arduino footpedal will be much more fun :)
> > 
> > Hmmm.
> > Instead of a pot on one of the analog inputs use a cheap shaft encoder
> > and count pulses.
> >
> This sounds intriguing. Right now I have an Arduino, and the reason I haven't used it is  because I tried hooking it up to a volume pedal and the noise was so intense it was spewing out MIDI messages constantly... unusable. I had considered rigging up a passive analog LPF, or maybe doing some smoothing in software on the Arduino, but ran out of time/patience.
> What would be involved in fitting this kind of encoder to a volume pedal? I can find guitar-style volume pedals easily, and they're cheap. The advantage is that I could use a very cheap ATTiny2313 with no ADC instead of an ATMega Arduino. Encoders sound like the way to go.
> > Double Hmmm
> > Fix it so that the index pulse is at exactly the halfway point in the
> > travel, and it will 'silently' re-calibrate itself every time you pass
> > throgh that point.
> > 
> I don't know what an "index pulse" is. If you could point me to some good introductory reading material on dealing with encoders, I'd find it very interesting indeed.
> Thanks.
> -ken

Hmmm. The best 'introductory' reading is probably on the arduino forums!

Basically, any half decent encoder has at least three outputs. A, B &
Z or N

A and B are the running pulses and are timed such that as well as
giving you a count, they can also tell you the direction. N or Z is the
index and occurs exactly once per revolution of the encoder.

So, as an example if you have a 500 pulse encoder and fix it to a
pedal so you have 180deg of movement you'll actually get a useful 250
pulses. Position the encoder shaft so that the index comes at 90deg and
you'll be able to count +/- 125 pulses and seeing as MIDI only gives
you 127 for most operations that's nearly twice what you need.

Hmmm again. I'm used to just handling these and not having to buy
them. Just looked up on RS and the cheapest one that fits the bill is
about 40 squids :(


Will J Godfrey

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