Pioneer Proof of concept

[brouhaha]

(01-23-2024 05:01 PM)HP-Collection Wrote:  Even the contacts on the PCB are not copper but black.

The black seen in other places on the PCB is a carbon coating most commonly seen for inexpensive membrane keyboards. It is somewhat resistive so it shouldn't be used in a production calculator for battery contacts, but in principle it would work well enough for a prototype.