PASCO EM-8656 AC_DC ELECTRONICS LABORATORY - Manual (Page 61)

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012-05892A AC/DC Electronics Laboratory
®
Experiment 15: Diode Lab – Part 1
EQUIPMENT NEEDED:
– Computer and Science Workshop™ Interface
– Power Amplifier (CI-6552A)
– (2) Voltage Sensor (CI-6503)
– AC/DC Electronics Lab Board (EM-8656)
– (2) Banana plug patch cords (such as SE-9750)
Purpose
In this experiment, the properties of various type of diodes are investigated.
Theory
A diode (or p-n junction rectifier) is an electronic device which only allows current to flow in
one direction through it once a certain forward voltage is established across it. If the voltage is
too low, no current flows through the diode. If the voltage is reversed, no current flows through
the diode (except for a very small reverse current).
A light-emitting diode emits light as current passes through the diode in the forward direction. A
red-green diode is actually two diodes connected together antiparallel so that the red diode
allows current to flow in one direction and the green diode allows current to flow in the opposite
direction. Thus, if DC (direct current) is applied to the red-green diode, it will be only red or only
green depending on the polarity of the applied DC voltage. But if AC (alternating current) is
applied to the red-green diode (bicolor LED), the diode will repeatedly blink red then green as
the current repeatedly changes direction.
A bicolor LED is an example of a Zener diode. A Zener diode allows current to flow in one
direction when the forward voltage is large enough, and it allows current to flow in the opposite
direction when reverse voltage (called the “breakdown” voltage) is large enough (usually a few
volts).
Overview
There are several units to the Diode Lab. You will complete the first two units in Part 1 (this
experiment). You will complete Unit Three and Unit Four in Part 2 (the next experiment).
Unit Activity
One diode properties
Two LED’s and Zener diode
Three rectify a sine wave
Four basic power supply
In the first unit you will investigate the general properties of a diode. In the second unit you will
investigate different types of diodes, including light-emitting diodes (LED’s) and a Zener diode.
In the third unit you will rectify a sine wave generated by the Power Amplifier. In the last unit
you will setup the basic circuitry for a power supply.