AC/DC Power Supply

Direct vs. Alternating Current

Graph of AC voltage over time

Period and Frequency

One cycle of a wave is one complete evolution of its shape until the point that it is ready to repeat itself.

The period of a wave is the amount of time it takes to complete one cycle.

Frequency is the number of complete cycles that a wave completes in a given amount of time. Usually measured in Hertz (Hz), 1 Hz being equal to one complete wave cycle per second.

Frequency = 1/(period in seconds)

Mutual inductance

Whenever electrons flow through a conductor, a magnetic field will develop

Mutual inductance is where the magnetic flux of two or more inductors are “linked”

A transformer is a device made of two or more inductors, one of which is powered by AC

If the second inductor is connected to a load, power will be electromagnetically coupled from the first inductor's power source to that load.

Transformer “transforms” AC voltage and current.

Able to step voltage up or down

The AC voltage induced in the unpowered (“secondary”) coil is equal to the AC voltage across the powered (“primary”) coil multiplied by the ratio of secondary coil turns to primary coil turns

AC Rectification

Rectification is the conversion of alternating current (AC) to direct current (DC).

A half-wave rectifier is a circuit that allows only one half-cycle of the AC voltage waveform to be applied to the load.

A full-wave rectifier is a circuit that converts both half-cycles of the AC voltage waveform. The resulting DC delivered to the load doesn't “pulsate” as much.

DC regulated power supply

110/220V switchable LED indicator Offers 3V, 9V and 12V regulated DC Maximum output current, 200mA

Voltage Divider

Breadboard Practice

Breadboard a voltage divider and measure voltage drops

Place a load on the voltage divider and measure voltage drops

Voltage Regulating ICs

LM 7805

Voltage Regulating ICs

Function: Generate a fixed output voltage regardless of changes to input voltage or load

Three main configurations

• BUCK (Step-down)

• BOOST (Step-up)

• BUCK-BOOST

Parts ListParts You Will Need

An Altoids Chewing Gum tin

A 9V battery (151095)

A 9V battery clip (109154)

A 7805 voltage regulator (51262)

A USB socket (161024)

A small switch (109171)

A 22kΩ Resistor (691180)

Two 27kΩ Resistors (691201)

A 39kΩ Resistor (691243)

~ 2 ft hook-up wire (36792)

Electrical tape (285464)

Metal shears (to cut the Altoids tin)

USB Charger

7805 Pinout