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

[Oren Leavitt]

I use those now and then - they are SMT only but work great for that 
kind of stuff.

https://www.ti.com/lit/ds/symlink/sn74hcs165.pdf

Nice work, Jean!


On 1/12/23 3:56 PM, Roman Sowa wrote:
> 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
>>
>>
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at synth-diy.org
>> http://synth-diy.org/mailman/listinfo/synth-diy
>> Selling or trading? Use marketplace at synth-diy.org
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org