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The Almanac

Rules of thumb, earned at the bench.

Our lessons and our mistakes, written down and shared, so the next project goes better than the last.

Vol. I · 2026Published by Verduzco Systems

Symptom

An indicator LED on a 5 V GPIO flashes bright once, then stays dark for good.

Root cause

Nothing limits the current. The LED pulls far past its rating and fails open.

Fix

Add a series resistor sized from (V supply − V forward) / I forward, with margin for the GPIO’s drive limit.