Electronics

Electricity is the flow of charge around a circuit carrying energy from a power source (battery) to components such as LEDs and motors.

Electricity (electrons) flow from negative to positive.

Voltage –the force or pressure needed to move electrons or the difference of potential energy that forces electrons to flow in a circuit. The unit of measure is the volt. (lake)

Current – the name given to the flow of electrons or the rate of flow of charge of electrons. Current is like the flow of water. The unit of measure is the Ampere. (River)

Resistance - restricts the flow of electric current. The unit of measure is the Ohm. (dam)

DC Electricity

Electronic ComponentsReview

Electrical Components and Their Characteristics Disclaimer

All electrical/electronic components require voltage and current to make them work. When working with electrical/electronic components it is VERY IMPORTANT to understand that these components will only work properly when the correct voltage and current are supplied to them.

All electrical/electronic components are RATED for a specific range of voltage and current. Exceeding these ratings results in decreased life expectancy or failure of the component.

Supplying Power to Circuits• Electronic components require a Direct

Current (DC) power source to operate. • It is EXTREMELY important to connect

POSITIVE and NEGATIVE up the correct way for components to work.

• Electronic devices such TVs, Stereos, DVD players and computers are plugged into an Alternating Current (AC) source. They require a conversion from AC to DC for them to work.

• This is the symbol for a DC power source that will be used in this class

LED(Light Emitting Diode)

• Gives off light when electricity flows through it. • Has a positive (Anode) and negative (Cathode) side.• Depending on the type of LED and colour, the voltage

drop across it can be anywhere from 1.7v to over 4v.• An LEDs voltage drop is important as you cannot use

Leds unless the power source is greater than its voltage drop.– Diffused red, green, yellow – 1.7-2v– Ultra bright 2-3v– White and Blue 3-4v

• Requires a resistor to limit the current going through it. Max current on standard LEDs is around 25mA. Usually run around 15mA – 20mA.

• Ohms Law – at a later date

Limiting Current using ResistorsResistors are an important part of electronics. They are used to control the amount of current being used in a circuit and specifically by components. Resistors come in different sizes (1/8, ¼, ½, 1, 5, 10watt….etc) and values (1 Ohm – 20M Ohm).

It is EXTREMELY IMPORTANT to match up a resistors wattage to the amount of current that will flow through it in a circuit.

Ohm’s Law and Watt’s Law will come Later

Potentiometer

• variable resistor, as you turn the knob, the resistance changes from 0 ohms (no resistance) to it’s maximum value (lots of resistance)

• Like a dimmer switch in a dining room

Light Dependant Resistor or Photocell• a special kind of resistor that reacts to light. The

more light that hits it, the less resistance it has.

• AN LDR has a maximum amount of current it can handle (depends on size)

• LDRs are rated differently SO you need to know what electrical characteristics they have before you use them.

• To check an LDRs resistance, put it in complete darkness to check its upper resistance (max) and in direct sunlight for its lower resistance (min)

• If its lower resistance is LOWER than the minimum resistance required to safely operate an LED in a circuit, then a resistor in parallel will be required.

Diode

• a diode is a device that allows current to flow through it in ONE direction only. There are two leads. The anode and cathode. The cathode is the silver band side.

Reading the Value on ResistorsResistor Colour Code

Why the Colour Code?

The Colour code was developed to overcome two basic problems;

• Difficult to print and see numbers on a small resistor• Even if you could see the numbers, placement on a

circuit board might hide the number

The Code

• When you read the colour code the resistor should be read with the gold (or silver) on the RIGHT!!

1st Digit

2nd Digit # of zeros

ToleranceGold +/- 5%Silver +/- 10%

1st Digit

2nd Digit # of zeros

ToleranceGold +/- 5%Silver +/- 10%

Black 0

Brown 1

Red 2

Orange 3

Yellow 4

Green 5

Blue 6

Violet 7

Grey 8

White 9

This resistor is read as;1st Digit is 12nd Digit is 3# of zeros is 2

Answer is; 1300 ohms +/- 5%

Acceptable range1235 ohms – 1365 ohms

ExamplesBlack 0

Brown 1

Red 2

Orange 3

Yellow 4

Green 5

Blue 6

Violet 7

Grey 8

White 9

1) Red, Red, Brown, gold220 ohm

2) Blue, Black, Orange, gold 60,000ohmOr 60K

3) Yellow, Violet, Yellow, gold 470,000ohmOr 470K

4) Brown, Black, Blue, gold 10,000,000ohm Or 10M

NOTE: when writing a resistor value, the extra zeroes are dropped in favour of Kilo = 1000 or Mega = 1,000,0001000ohm = 1k

1,000,000ohm = 1M

5) Grey, White, Red, gold 8900 ohmOr 8.9K

Examples

• Red red brown• Green, blue, red• Orange, black, black• Yellow, violet, orange• Green, grey, yellow• Blue, white, red• Violet, red, black

• Brown, black• Red, red, green• Grey, white, yellow• Orange, orange, blue• Yellow, orange, red• Red, grey, green• Green, blue, brown

Capacitors• A device used to store energy much like a

battery. Can be charged and discharged over and over.

• There are different types;– Electrolytic

– Ceramic Capacitors

– Film Capacitors

– Polyester Film Capacitors

– Tantalum Capacitors

Electrolytic Capacitor• It is easy to find the value

of electrolytic capacitors because they are clearly printed with their capacitance and voltage rating.

• The voltage rating can be quite low (6V for example) and it should always be checked when selecting an electrolytic capacitor.

Disc CapacitorsReading a Disc Capacitor• A number code is often used on small

capacitors where printing is difficult: – the 1st number is the 1st digit, – the 2nd number is the 2nd digit, – the 3rd number is the number of zeros to

give the capacitance in pF. Just like Resistor Colour Code.

– letters indicate tolerance and voltage rating.

• For example: • 103Z means 10000pF = 10nF (not 103pF!)

and the Z means -20 + 80% tolerance).

Film CapacitorsCan be read the same as electrolytic or disc capacitors depending on the size of it. Sometimes the multiplier is used in place of the decimal point:

For example: 4n7 means 4.7nF.

When all else fails

http://library.solarbotics.net/pieces/parts_elect_pass_cap_code.html

USE a Multi-meter

Converting UnitsmicroFarads (µF) nanoFarads

(nF) picoFarads (pF)

0.000001µF = 0.001nF = 1pF

0.00001µF = 0.01nF = 10pF

0.0001µF = 0.1nF = 100pF

0.001µF = 1nF = 1000pF

0.01µF = 10nF = 10,000pF

0.1µF = 100nF = 100,000pF

1µF = 1000nF = 1,000,000pF

10µF = 10,000nF = 10,000,000pF

100µF = 100,000nF = 100,000,000pF

Tolerance Codes

Tolerance Code ToleranceC +/- 0.25pFD +/- 0.5pFF +/- 1%G +/- 2%J +/- 5%K +/- 10%M +/- 20%Z - 20% +80%

SCRSilicon-Controlled Rectifier

• allows current to flow through it ONLY after a positive voltage is applied to the gate. It will continue to conduct until the power is CUT to the circuit.

• The SCR is like a Diode and LED in that the Anode and Cathode have to be connected the correct way for electricity to flow through it.

Switches

Toggle Switch Push Button

NPN Transistors• the transistor works as a current amplifier. It uses

a small amount of current to control a larger current.

• When the emitter of the transistor is connected to ground, and the base is connected through a resistor to positive, a small amount of electricity flows. When this electricity flows, it opens up the collector to allow an amplified current to flow from the emitter to collector.

• Transistors can be used as switches to turn on/off other devices

• The size of a transistor limits the amount of current that can flow through it.

NPN Transistors• A transistor is typically connected up like the

one to the right. As the base current flows from the emitter (negative) through the base, it allows current to also flow from the emitter through the collector.

• The more current that flows through the base, the more current flows through the collector. However, at some point the transistor is fully turned on (saturated).

• If too small a value of resistor is used, TOO much current can flow through the base and you will burn out the transistor!!

Material Code

Marking Material

MKT, MMK, MDK Metallised Polyester (PETP)

MKC Metallised Polycarbonate

KT Polyester Film / FoilKS Polystyrene Film / Foil

KP Polypropylene Film / Foil

MKP Metallised Polypropylene

Transistor

• the transistor works as a current amplifier. It uses a small base current to control a larger current.2n3904 NPN Transistor 2n3906 PNP Transistor

Integrated Circuit

• a device that has several components (transistors, resistors, capacitors, diodes, etc) condensed into a very small package. Each IC performs differently according to what is inside.

Integrated Circuits

• To figure out which pins are which, the text faces so you can read it, or the notch, dot, line is on your left.

• Pin #1 in therefore on the bottom left corner

Integrated Circuits

• Once Pin #1 is established you read from left to right on the bottom then right to left on the top

Batteries• Batteries can only supply a specific

amount of electricity at its rated voltage for a certain period of time before they die.

• The larger the battery, the more electricity it can hold.

• When designing portable devices this knowledge is EXTREMELY important.

• The table to the right shows the typical capacity of an average battery off the self at a store.

Battery Type

Capacity (mAh) Volts

Typical Drain (mA)

D 10000 1.5 500C 5000 1.5 500

AA 1300 1.5 500AAA 1200 1.5 25

9 Volt 600 9 25