RPN-duino

[Chasfield]

I have just completed a third RPN-duino calculator design. This is implemented using a full sized Arduino Uno board with a SainSmart 1602 keypad/LCD shield installed on top. Another Rockwell 4-function calculator was plundered for its excellent modular keyboard (I keep getting these weird e-mails from the RUG, whoever they are, saying they know where I live). The case was hand-built around the Arduino stack and keyboard, from hardwood strip, sandwiched between a base and bezel of 2mm plastic sheet.

There are a couple of advantages to this approach. The unit is more compact, despite the full size Uno board being used, instead of the Nano of previous designs. Wiring the thing up was trivial by comparison, requiring only 9 keyboard lines, a battery clip and switch.

The main drawback is increased current consumption. The Uno/SainSmart combo needs around 65 mA, so ten hours of battery life is expected. My previous Arduino Nano based calculators only pulled half that.