Power Stations House

Generators

Alternating Current & Voltage

AC Power (Wikipedia)

• In a three-phase system, three circuit conductors carry three alternating currents (60 Hz) which reach their instantaneous peak values at one third of a cycle from each other. This makes it possible to produce a rotating magnetic field in an electric motor.

• Three-phase systems have a neutral wire. A neutral wire allows the three-phase system to use a higher voltage while still supporting lower-voltage single-phase loads.

• Most household loads are single-phase.

2 Phase Y Configuration

120/240 AC Volts

The Standard 3 prong outlet.

Wiring the

Outlet

Electrical Lab Safety1. Electricity can kill you, especially alternating

current!

2. Current can pass from your hand through your feet to ground, or through your heart to your other hand.

3. Capacitors can hold kilovolts of charge for years.

4. Static electricity, generated by your feet on a carpet, can produce kilovolts that can fry solid state electronics.

5. Wear shoes on a dry floor, use one hand.

DC Circuit Components

Voltage Sources

Bio-Electronics for Scientists 1

Batteries and Source Resistance

Batteries• An electric battery is a device consisting of

one or more electrochemical cells that convert stored chemical energy into electrical energy.

• Each cell contains a positive terminal, or cathode, and a negative terminal, or anode.

• Electrolytes allow ions to move between the electrodes and terminals, which allows current to flow out of the battery to perform work (wiki).

• Batteries convert chemical energy directly to electrical energy.

How Batteries Work• Each cell consists of two half-cells connected in series by a

conductive electrolyte containing anions and cations. • One half-cell includes electrolyte and the negative electrode,

the electrode to which anions (negatively charged ions) migrate; the other half-cell includes electrolyte and the positive electrode electrode to which cations (positively charged ions) migrate.

• Redox reactions power the battery. • Cations are reduced (electrons are added) at the cathode

during charging, while anions are oxidized (electrons are removed) at the anode during discharge.

• The electrodes do not touch each other, but are electrically connected by the electrolyte. (wiki)

Battery Types: Primary• Primary batteries, or primary cells, can

produce current immediately on assembly.

• Disposable primary cells cannot be reliably recharged, since the chemical reactions are not easily reversible and active materials may not return to their original forms.

• In general, these have higher energy densities than rechargeable batteries.

• Common types of disposable batteries include

zinc–carbon batteries and alkaline batteries. (wiki)

Battery Types: Secondary• Secondary batteries, also known as secondary cells, or

rechargeable batteries, must be charged before first use; they are usually assembled with active materials in the discharged state. Rechargeable batteries are (re)charged by applying electric current, which reverses the chemical reactions that occur during discharge/use. Devices to supply the appropriate current are called chargers.

• The oldest form of rechargeable battery is the lead–acid battery: the modern car battery can deliver a peak current of 450 amperes.

• Mobile phones and laptop computers use (in order of increasing power density and cost) nickel–cadmium (NiCd), nickel–zinc (NiZn), nickel metal hydride (NiMH), and lithium-ion (Li-ion) cells. (wiki)

The Oscilloscope

Multimeter (digital)

Power Supply & Function

Generator

Unit Analysis• One of the most important things to do in

manipulating equations involving physical entitites like power and energy (and everything is science) is unit analysis.

• Unit analysis means putting the correct units of various quantities in your equations, and making sure that the unit type carried through the equation is correct.

Unit Analysis: An example• The watt (symbol: W) is a derived unit of power in the

International System of Units (SI), named after the Scottish engineer James Watt (1736–1819) measures the rate of energy conversion or transfer.

• One Watt is defined as one joule per second.• One watt is the rate at which work is done when one ampere

(A) of current flows through an electrical potential difference of one volt (V).

• Typical large power plants generate about 1000 megawatts.• In your electric bill you pay for kilowatt hours at a rate of about

5 cents per kilowatt-hour.• Given that watts is joules per second, and you pay for watts

time hours, you pay for joules, or total energy.

Analog vs. Digital Circuits

• Analog circuits usually have continuous values and are ‘analogs’ of what they control. For example, a knob varies a resistance which varies the current through a light bulb, dimming it.

• Digital circuits implement Boolean logic functions with all or none states corresponding to 0 or 1. While there were once analog computers, now virtually all computers are digital, such as TTL and CMOS.

• The interface between the world and digital circuits is done via analog to digital and digital to analog converters.

Devices for Analog Circuits• Analog circuits use:

1.Operational amplifiers (opamps, which are composed of transistors and resistors)

2.Transistors

3.Resistors

4.Capacitors

5.Inductors (rarely)

Digital Logic Gates

Implement Boolean

Functions such as these

Transistor–transistor logic (TTL)• Transistor–transistor logic (TTL) is a class of digital circuits

built from bipolar junction transistors (BJT) and resistors. • It is called transistor–transistor logic because both the logic

gating function (e.g., AND) and the amplifying function are performed by transistors (contrast with RTL and DTL).

• TTL is notable for being a widespread integrated circuit (IC) family used in many applications such as computers, industrial controls, test equipment and instrumentation, consumer electronics, synthesizers, etc.

• The designation TTL is sometimes used to mean TTL-compatible logic levels, even when not associated directly with TTL integrated circuits, for example for the properties of the inputs and outputs of electronic instruments.

TTL NAN

D Gate

TTL Interface Properties• TTL is a current-sinking logic since a current must be drawn

from inputs to bring them to a logic 0 level. • At low input voltage, the TTL input sources current which must

be absorbed by the previous stage. The maximum value of this current is about 1.6 mA for a standard TTL gate.[17]

• The input source has to be low-resistive enough (< 500 Ω) so that the flowing current creates only a negligible voltage drop (< 0.8 V) across it, for the input to be considered as a logical "0".

• If a TTL inputs is simply left floating it will provide a logical "1", though this usage is not recommended.

• Standard TTL circuits operate with a 5-volt power supply. A TTL input signal is defined as "low" when between 0 V and 0.8 V with respect to the ground terminal, and "high" when between 2.2 V and 5 V.

CMOS• Complementary metal–oxide–semiconductor (CMOS) is a

transistor technology for constructing integrated circuits. • CMOS technology is used in microprocessors, microcontrollers,

static RAM, and other digital logic circuits. • CMOS is also sometimes referred to as complementary-

symmetry metal–oxide–semiconductor (or COS-MOS).[1] The words "complementary-symmetry" refer to the fact that the typical digital design style with CMOS uses complementary and symmetrical pairs of p-type and n-type metal oxide semiconductor field effect transistors (MOSFETs) for logic functions.[2]

CMOS Characteristics• Two important characteristics of

CMOS devices are high noise immunity and low static power consumption.

• Since one transistor of the pair is always off, the series combination draws significant power only momentarily during switching between on and off states.

• CMOS also allows a high density of logic functions on a chip, primarily for this reason that CMOS became the most used technology to be implemented in VLSI chips.

Interfacing TTL & CMOS

The Diode (rectifier for power)

LEDs (light emitting diode)

How Things are Made: The Lathe

How Things

are Made:

The Milling

Machine

Series Resistors

Parallel Resistors

Current Sources

AC Circuits

Capacitance

AC Circuits & Energy Storage

Capacitance

Cable properties

Electronic (Resistive) Noise

Resistive Noise