Electronics Puzzler: Hit the Bulls Eye

By Forrest M. Mims III
Bulls Eye

What is the simplest way to light the LED when a ball strikes the bull's eye?

A fictional engineer we'll call John Archer spent a decade designing hardware and writing code for microprocessor-controlled games manufactured by a toy company. Citing a market for "back to basics" toys, the company president said he wanted to introduce a new line of simple games that would flash a red LED when a target was struck by a rubber band, rubber ball or other reasonably safe projectile. The catch: The game should not use a battery or external source of power. How did Archer solve this very different assignment?

Puzzle Hints
John Archer was so immersed in designing complex hardware, writing code and laying out multi-layer PC boards that his new assignment caught him off guard. While he could think of many ways to solve the problem, they all required a battery or an external source of power. While day dreaming about possible solutions, his watch sounded an alarm to remind him about an important meeting to discuss the project. While entering the security code to open the meeting room door, he suddenly thought of a solution.

What is your solution to this problem?

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