C64 Cynthcart Controller

[fredrik]

You can power it with 5 V no problem, and the circuit isn’t using a lot of power so using the C64 supply should be ok.

However, note that the Arduino power is misconfigured; you should supply +5V to pin 27 (+5V), not pin 30 (VIN). See here:

Design glitches: Arduino Nano supply voltage

(thought I’d collect my nano supply notes in one place to make it easier to link to) A common design glitch in circuits that use an Arduino Nano is to connect regulated 5 V to the VIN pin instead of the +5V pin. This results in the Arduino running at a lower internal supply voltage, often 4 V or below, which may be a problem if the design depends on analog inputs or digital output levels. Voltages below 4.5 V are also out of spec for the 16 MHz clock used by the Nano. Details below, but TL;DR …

Using 100k instead of 10k may cause problems, though; the analog inputs on the Arduino have a sample and hold circuit with a small capacitor, and they recommend that the circuit driving the input has an impedance <10k. See here:

Arduino based ADSR

10k is a good default. You can use higher values, but the analog read samples the input by very briefly charging a (tiny) capacitor, so if you go too high it may not charge up properly, and the channels may start affecting each other. The usual fix for that is to add external capacitors. [image] EDIT: Added input circuitry.

EDIT: To clarify, the maximum output impedance of a potentiometer divider is R/4 (half the resistance in parallel with the other half), so a 20k potentiometer would be ok, but 100k is pushing it.