I am building a MIDI merger / filter in order to mix MIDI data from an old Ibanez MC1 - guitar to MIDI converter with data from the Arduino MIDI controller shown last video.
The idea is to expand the control change messages available and also allow the use of expression pedals and potentiometers.
When I was about to build the MIDI circuit on the breadboard, I remembered that the last appropriate optocoupler I had was already used in the Arduino MIDI controller.
So, I decided to try some old 4N25 optocouplers I have dozens here in stock.
It is a six pin IC, just the LED and a photo-transistor with base, collector and emitter pins.
In terms of performance, the 4N25 is a bit on the slow side.
It works without problem with just a 1K pull-up resistor on the collector, and the emitter grounded, but there are ways to make its transitions faster using the available base pin.
Or I could just follow it with a Schmitt trigger IC, if I had one here...
A quick search on the internet showed me a variety of circuits, from which I chose two for this experiment.
The tests were conducted using the MIDI output from the Arduino MIDI controller connected to the 4N25 circuits (one at a time), and finally to the RX1 pin on an Arduino Mega2560.
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Thanks for watching.
