[sdiy] Alternatives to Faders

[Tom Wiltshire]

Edward,

On 7 Mar 2007, at 20:43, Edward King wrote:
>
>> A final problem that your recycled-mouse idea might have avoided is 
>> that commercial rotary encoders often don't have that many positions 
>> per rotation - 24 pulses per rotation is a common value, although by 
>> no means the only one available. This makes doing large changes of 
>> high resolution controls quite difficult. If the control has a 16 bit 
>> resolution and one full turn takes you from 0 to max (65536) then 
>> each of the 24 clicks represents 2730 units. How then to make a 
>> parameter value jump 2730 units without an abrupt change?
>>
>> Sorry not to offer more positive suggestions, but this is definitely 
>> still a problem for which a really good solution is yet to be found.
>
> I think theres some confusion here about position sensing and rate. 
> Ball mice feed rate data back (the amount that their position has 
> changed since the last 3 byte value) not absolute position.
> Because you're measuring rate of change rather than absolute position, 
> moving the wheel slowly gives you fine control and moving it quickly 
> gives you coarse control.
> If you really want the parameter to jump from 0 to max, just flick the 
> wheel forward and you get the abrupt change you desire.

Yes, I see what you're getting at now. Whilst there are absolute 
position rotary encoders available, I was thinking of the kind that 
output two pulse trains 90 degrees out of phase. I'd been thinking of 
simply counting the pulses to give you relative position information 
(move +5, or move -15, for example) but I can see that measuring the 
_rate_ of those output pulses is in many ways more useful. As you 
suggest, you can map the rate information to the increment, so that 
faster movements take you further, and slower movements steps through 
the values one by one.

Thanks, I'll have to think about this some more...

Regards,
Tom

PS: Btw, it was me mentioned hexadecimal. All I meant was that 255 is 
only a number that has significance in binary/hex/octal - I wasn't 
suggesting anyone would actually display anything in hex. Imagine: Mod 
depth=2C! yurg!


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