[sdiy] Pots vs Encoders, was Re: [sdiy] dave smith *instruments*

[cheater cheater]

Amos,
you can get away with one pwm per led ring. 0 means the 'lower' led, 1
means the 'higher' led. Then you'd need some way of switching which
leds are being addressed. But once you have this in place you would
notice that when you arrive at the second led, i.e. the pwm signal is
all 1's, then you'd have to synchronize the switch of which led is
addressed by a 0, with changing the pwm to constant 0. So maybe an
even better idea would be to start out on the first led and assign 0
to it, and assign 1 to the second led, then slowly rise the pulse
width value towards the signal being constant 1. Once this happens,
switch the led addressed by the value 0 to the third led. This way
every second led is only ever addressed by value 0, and every second
by the value 1. This is a big improvement from the 'trivial' way I
described in the beginning which required each value to address each
diode (except for the first and last diode). This means that for 32
leds, 16 of them would have to be addressed from the 0 and 16 from the
1, they are switched around separately, which would allow you to keep
the complexity down to a similar level as with just switching around
one lit diode across all 32 possible places. This would be, I think, a
good idea.

HTH
D.

On Thu, Feb 4, 2010 at 01:34, Amos <controlvoltage at gmail.com> wrote:
> Very interesting idea!  You could do the "interpolation" idea with no
> extra hardware requirements.  The brightness idea is interesting also,
> but you'd need to be creative... 15 pwm channels (one for each LED in
> a ring) just for feedback from one pot, would be a bit extravagant.
> :-)
>
> You could use one PWM for the whole ring assuming you still only have
> one LED lit at a time... But what would brightness mean in this
> context? It would make more sense to have a dim LED next to a bright
> one, but the you're back into a more hardware-intensive situation.
>
> Excellent food for thought...
>
> -Amos
>
> On 2/3/10, Tom Wiltshire <tom at electricdruid.net> wrote:
>> If you used PWM to control the brightness of the LEDs, the 'extra'
>> resolution would be the resolution of the PWM - 8 or 10 bit is easily
>> possible.
>>
>> You wouldn't be able to tell much beyond 16 or 32 levels though, I'd
>> have thought. The effect would just get smoother looking. Still, it's
>> a good idea.
>>
>> T.
>>
>>
>> On 3 Feb 2010, at 23:39, cheater cheater wrote:
>>
>>> I wonder what is actually the maximum bit depth available with this
>>> sort of approach. Anyone know what the accuracy improvement with this
>>> sort of... hmm.. how do we call this? Anti-aliasing? Interpolation?
>>>
>>> D.
>>>
>>> On Wed, Feb 3, 2010 at 21:26, Ingo Debus <igg.debus at t-online.de>
>>> wrote:
>>>>
>>>> Am 02.02.2010 um 15:22 schrieb Tom Wiltshire:
>>>>
>>>>>  you typically get 15 or 31 LEDs around the ring, which is 5-bit
>>>>> accuracy
>>>>> at best
>>>>
>>>> Only if you allow only one LED lit at a time. If you allow one or
>>>> two lit
>>>> (one = spot on, two = value is in between) you get almost twice the
>>>> resolution. If you can control the LEDs' brightness you can get
>>>> even more.
>>>>
>>>> Ingo
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