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

[Oren Leavitt]

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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