Eye-Controlled LED

Introduction

LEDs (Light Emitting Diodes) are light sources made from a special semiconductor material that converts electrical current directly into light. You can turn an LED on and off by blinking your eye. An EKG sensor is normally used to record the muscle activity of the heart, but it can also record other electrical changes in your body, such as an eye blink. The retina of the eye maintains a charge across its surface giving the eyeball a small electrical dipole moment. The Vernier EKG Sensor is capable of detecting changes in this dipole moment as the eyes blink. When the eyes close a positive voltage pulse is produced in the EKG Sensor and as they reopen a pulse of opposite polarity is produced. As a STEM extension to the “Monitoring EKG” experiment, you will illuminate an LED in the Vernier Digital Control Unit (DCU) when you blink your eye.

Objectives

• Turn on an LED by blinking your eye.
• Control a sensor-based system with the DCU.

Reference Experiment

• “Monitoring EKG” – Experiment 28 from Biology with Vernier
• “Analyzing the Heart with EKG” – Experiment 12 from Human Physiology with Vernier