museum electronics arduino led calculator museum maker lmn impression5

Impression 5 Giant Calculator

March 5, 2020 complete
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Overview

The Impression 5 Science Center in Lansing, MI operates an oversized calculator exhibit that lets visitors perform arithmetic on a human-scale input panel. This project is the Arduino Mega–based electronics replacement for that exhibit’s controller.

The original display electronics wore out and needed a from-scratch reimplementation. The new controller drives a custom LED display panel, reads a physical keypad, and handles big-number arithmetic — necessary because exhibit visitors happily type 15-digit numbers and expect correct results.

Architecture

The firmware is split into focused modules:

  • LEDdisplay — drives the multi-digit LED display, mapping digits to segment outputs
  • Calculator — arithmetic engine; handles addition, subtraction, multiplication, and division
  • BigNumber — arbitrary-precision number representation (wraps a C big-integer library) so the display never overflows silently
  • Mega_Calculator.ino — top-level sketch wiring it all together

Hardware

  • Arduino Mega 2560 — needed for the I/O count (keypad rows/columns + multiple display driver pins)
  • LED 7-segment displays — driven via the custom LEDdisplay module
  • Physical keypad — numeric digits 0–9, operators (+, −, ×, ÷), equals, clear

Companion PCB

The SMASH Shield is the Eagle CAD Arduino Mega shield PCB designed for this and other Impression 5 projects, providing standardized connectors for display panels, keypad wiring, and power.

This project is part of a family of Lansing Makers Network contributions to Impression 5, alongside the Genome Map interactive exhibit.