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

[Roman Sowa]

If you need Schmitt inputs on shift register, try 74HCS165, having all 
Schmitt inputs.
although I'm not sure if it's available in DIP.

Roman

W dniu 2023-01-11 o 23:39, Jean-Pierre Desrochers pisze:
>
> Winter.. what a good time to work on my electronic projects!
>
> I'm taking the opportunity right now to polish up my old piano roll 
> reader project
>
> for earlier mechanical piano. This project will be able to read the 
> scrolling vintage music paper rolls
>
> containing piano notes and hear them using an external MIDI player.
>
> My prototype takes up a large part of my desktop space,
>
> but it's going well so far.. A big challenge to take up..
>
> From the start I faced 2 problems: First, The IR beams reading 
> strength of each holes
>
> to be read. I managed it using short 2mm ‘light pipes’ between the 
> photo-transistors
>
> and the IR emitting leds to ‘channel’ the light. Second, The SPI 
> parallel to serial
>
> 74HC165’s have no Schmitt trigger inputs so… LOTS of jitter readings 
> making the holes readings
>
> Completely unreliable. The solution.. inserting 74HC14 schmitt 
> inverters between
>
> The photo-transistors and the HC165 inputs. Voilà !
>
> Of Note: The bottom photo shows the paper roll installed and ready to 
> play..
>
> notice the little purple lights above the paper..
>
> these are infrared LEDs invisible to the naked eye but visible to the 
> camera..
>
> Have a nice 2023 beginning everybody !
>
> JP
>
>
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