[sdiy] Reading holes (voids) on piano paper rolls.. using Photo-transistors and PIC micro..

[Oren Leavitt]

Another option, would be to use a large area light source - LED with a 
diffuser about the size of a single hole.

The thin separator between holes of a continuous will not cover the 
light source enough for the photo transistor to turn off.

On 11/10/22 9:01 PM, Oren Leavitt via Synth-diy wrote:
>
> Using option #2, I would make the software aware of the roll speed - 
> e.g. get pulses/ticks from the roll drive
>
> Use the rate of the ticks to determine a minimum skip time based on 
> roll speed
>
> - Oren
>
> On 11/10/22 7:56 PM, Jean-Pierre Desrochers wrote:
>>
>> Hi all,
>>
>> My Player piano reader project is going fine so far..
>> Some little robotics stuff (stepper motors, sensors, etc..) going on 
>> now..
>> I’m now in the process of reading the small holes scrolling
>> with the music paper rolls ‘sandwiched’ between Infrared leds and 88 
>> x Photo transistors (see the image below).
>>
>> The actual music data appears on the paper as parallel lines of small 
>> successive holes
>> shown in blue below. Because of the need of paper sturdyness for long 
>> duration notes the original paper punches
>> made small successive holes in the same note line instead of a steady 
>> cut in paper
>> that could eventualy be damaged over time..
>> That is shown by the blues dots below (successive holes).
>> Now I need to read these constant note ‘ignoring’  all the occuring 
>> small holes
>> during these long  duration notes..
>>
>> The second line shows what the reading Photo transistor ‘sees’
>> and the third line shows an ideal reading stored in the micro.
>> *So far there are 2 ways I found to get close of the ideal reading :*
>>
>> *#1  Place a capacitor in parallel with each Photo transistors to get 
>> rid of the ‘pulsating holes’ on a continuous note*
>>
>> *#2  Use software with separate counters to ‘skip’ the incoming small 
>> pulses just enough not to miss any ‘real’ short notes.*
>> My challenge here is that the paper roll speed will be a variable one
>> which could be varied from *1feet/min*  up to *13feet/min*.
>>
>> That’s a  1 to 13 ratio !!
>> So method #1 using caps in parallel with the photo-transistors (fixed 
>> RC time)  will not be feasable (I think).
>> Is there another way you could think of to get rid of these small pulses
>> when necessary ?
>> Thanks !
>>
>>
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