Hands-On-Physics

Introductory Electronics Unit
Core Project:
INTRODUCTION


Background:

The first part of this circuit, the transformer, reduces the voltage coming from the outlet. However, it is still an alternating current, not a direct current. The bridge rectifier flips the negative voltage to positive;

so the waveform goes from a sine wave:

to the absolute value of a sine wave:

The capacitors smooth out the peaks and valleys to a steady voltage. The voltage regulator chops off the parts above the voltage you want, which is why there is a heat sink attached to it. It is also possible for the voltage regulator to carry a small voltage and give you a small shock. The potentiometer lets you control the voltage.

A Story

You are designing a security system to protect Bill Gates' estate. When triggered, the alarm system sends a message directly to the police. However, you want audible alarms as well, so the intruder knows she is in deep trouble and flees rather than continues on in. You want the alarm loud on the outside speakers, but softer at interior locations. You can achieve this by controlling the voltage to each speaker. You may use a LVPS at the interior locations so the volume of the alarm is adjustable by Bill and his family, depending on where they are.

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