ELECTRONICS CLUB

IIT JODHPUR

Digital electronics

Content...

1) Breadboard2) Resistors and Capacitor3) Digital4) Clock Pulse5) Logic Gates6) 555 timer7) Decade counter8) Decoder9) 7 segment LED display10) Digital clock workshop

BREADBOARD

WHY BREADBOARD..??

• Bread + Board •Strip of metal (copper usually) runs underneath the board connecting the holes to one another.

• Used to connect a circuit to reduce use of wires.• Easy to modify the circuit in case of errors.• No soldering required• Since it is not permanent, can be reused.• Not used for professional purposes

Resistors…

B B ROY of Great Britain has a Very Good Wife

Types of Resistors

FIXED RESISTORS:1) Carbon Composition Resistor2) Precesion wire wound3) NIST Standards4) Power wire wound resistor5) Fuse resistors6) Carbon film resistors7) Metal Film resistors 8) Foil Resistors9) Filament resistors10) Power Film resistors

VARIABLE RESISTORS11) Rheostat12) Potentiometer13) Preset

Capacitance..• Capacitance is the measure of capacitor to STORE CHARGE. •Units of capacitance Farads, pF, uF

• Q= C*V

• Charging and Discharging• Also used for coupling• Allows AC to pass through and blocks DC.

TYPES OF CAPACITOR

1) Electrolytic capacitor2) Non- Electrolytic capacitor3) Variable Capacitance (varicap) Other types capacitor Ceramic Capacitor Mica Capacitor Mylar Capacitor Dielectric Capacitor Film Capacitor Radial Lead type capacitor Axial Lead type capacitor Tantalum Electrolytic Capacitor

LETS BEGIN THE MAIN SECTION…!!

• DIGITAL

• ANALOG

DIGITAL ELECTRONICS

Digital electronics represent signals by discrete bands of analog levels, rather than by a continuous range. All levels within a band represent the same signal state.

If the individual values of the signal at the various intervals are approximated to certain precision rather than being noted precisely, the resultant signal is called a digital signal, the process being called quantization.

DIGITAL ELECTRONICS

• Consists of only two states.• Low state refers to 0 V.• High state refers to 5 V.

DESIGNING A DIGITAL CLOCK

APPLICATIONS•Small and Inexpensive •Digital Clock •Timers in Microwaves, cars ,televisions, AC etc

What do we need?

•A display

•Something that counts – Counter

•Speed controlling of counter

HOW DO WE COUNT..???

Using a 4029 counter

How to generate Clock ?

555Astable mode

OUTPUT

TIME TO DISPLAY

555

FINAL CIRCUIT

CLOCK

• In digital electronics, system clock is the basic timing unit. •System clock is a device which generates a periodic train of clock pulses. •The basic time interval during which logic operation must be performed is called clock cycle time.

clock cycle time = 1 period of clock waveform

CLOCK PULSE

INTEGRATED CIRCUITS (IC)• Integrated circuit originally referred to a miniaturized electronic circuit consisting of semiconductor devices, as well as passive components bonded to a substrate or circuit board.

• In short, a package of complex circuit to perform a task. • The circuit in the IC may be even more tiny but it is enclosed in bigger box for ease of handling.

• It can be considered to be a black box doing you work..!! :P

GATES Any binary operation (addition, multiplication etc) can be implemented using logic gates.

Basic Gates

AND OR NOT

Derived Gates

NAND NOR Ex-OR

VOLTAGE REGULATOR

• It produces fixed DC output voltage from variable DC. •A device which converts pulsating DC to fixed DC at output.

• Mainly two types - Fixed - Variable

FIXED 1) 78XX series is positive voltage regulator. 2) 79XX series is negative voltage regulator.

• 1st 2 digits indicate the sign and XX indicates the output voltage.

Eg. IC 7805- +ve voltage regulator giving +5V at output.

555 TIMER ORCLOCK PULSE GENERATOR

Used to generate clock pulse

So it is most commonly used IC.

PIN CONFIGURATION

BLOCK DIAGRAM

• Name 555 due to 3 5kohm resistor potential divider circuit.

• Consists of 2 OPAMP used as comparator, 1 flip flop and a discharge transistor. •Comparator used to compare the voltage at input and give output accordingly.

• Flip flop is bistable multivibrator (both states are stable).

• Non-inverting terminal of Comp1 is at +Vcc/3 .• When trigger input voltage (pin 2- inverting terminal) voltage is slightly less than +Vcc/3 resets flip flop (R=1) Q=0 transistor cut off Capacitor charges

• Inverting terminal of Comp2 is at +2Vcc/3.• When threshold voltage (pin 6- non inverting terminal) voltage slightly more than +2Vcc/3 sets flip flop (S=1) Q= 1 transistor saturates Capacitor discharges.

• Pin 1 Ground• Pin 8 +Vcc• Pin 4 Reset (if gnd, prevents device from working)• Pin 3 Output

APPLICATIONS• Monostable Multivibrator• Astable Multivibrator• Voltage controlled divider• Pulse position modulator (PPM)• Pulse amplitude modulator (PAM)• Frequency shift keying (FSK)• Ramp generator

MONOSTABLE MULTIVIBRATOR• Pin 6 and 7 are shorted.• 1 stable state.• Transistor changes state when trigger is given.• Produces gating pulse.

ASTABLE MULTIVIBRATOR

• Pin 2 and 6 are shorted• Also called ‘Free running multivibrator’• Both states are temporary.• The states keep changing without trigger pulse.

• A duty cycle is the time that an entity spends in an active state as a fraction of the total time under consideration. Duty cycle = (W/T)* 100 = (R1+R2)/ (R1+2R2) *100 = 0.693 (R1+ 2R2)*C

Frequency, f = 1.44__ [(R1+2R2)*C]

T – time period W – Width R1, R2 – Resistances in ohms C – Capacitance in farads f – Frequency in hertz

The time period can be split into two parts: T = Tm + Ts Mark time (output high): Tm = 0.7 × (R1 + R2) × C1 Space time (output low): Ts = 0.7 × R2 × C1

LETZ BEGIN FIRST STEP….!!

GENERATE CLOCK PULSE..!!

COUNTER• It is a special kind of register, designed to count the number of clock pulses arriving at its input.

Applications: 1) To count number of clock pulses. 2) To measure frequency. 3) For frequency division. 4) Measurement of time. 5) To generate a pulse of known width. 6) To generate timing pulses for horizontal and vertical generator in TV. 7) For direct counting of objects moving at a high speed. 8) In digital voltmeter etc.

MODULUS OF A COUNTER: • The modulus of a counter is the total number of states through which the counter can progress.• The natural count is given by 2^n, where n is the number of flip flops used.

TYPES OF COUNTER:

1) Ripple or asynchronous counter2) Synchronous counter3) Combination counter

DECADE COUNTER• It has a modified count. •By using 4 negative edge triggered J-K flip flops, Mod- 16 counter can be constructed.

• By using feedback, 6 states are skipped making it Mod-10 counter.

Up- Down Counter- IC 4029• Synchronous counter so its output changes precisely together with change in clock pulse.• The count occurs as clock input becomes high (positive edge triggered).• Up/Down determines the direction of counting: High Up 4 bit binary 0 to 15 Low Down decade 0 to 9

• Preset and Carry in terminal is low for normal operation.

PIN CONFIGURATION

Gives 4 bit BCD (Binary Coded Decimal) output.

PIN 1- Preset – GroundPIN 2, 6, 11, 14 – OutputPIN 3, 4, 12, 13 – Input – GroundPIN 5 – Carry In – OpenPIN 7 – Carry out – OpenPIN 8 – GroundPIN 9 – binary/decade – LowPIN 10 – up/down – HighPIN 15 – ClockPIN 16 - +Vcc

PIN CONNECTIONS

LED Display

PIN FUNCTION 1 Segment E 2 Segment D 3 Common Anode 4 Segment C 5 Decimal point 6 Segment B 7 Segment A 8 Common Anode 9 Segment F 10 Segment G

• Types of LED display - Common anode type. - Common cathode type.

• We will be using common anode type.• Active- low output decoder is used for common anode type display.• Current limiting resistors are connected between LED and ground.

NOW WE CAN COUNT THE CLOCK PULSE…

BUT IN BCD CODE…

WE NEED IN 7 Segment…

WHAT NOW…???

IC 7447 Pin Configuration

IC 7447• IC 7447 is used to convert BCD to 7- segment code.• It has 4 input lines and 7 output lines to drive 7 segment display.• The output terminals are connected to respective segment (a through g) of the display. • It is active- low output decoder.

• LT (Lamp Test) : Used to check the segments of LED display. Connect LT to logic 0 to check. Usually it is connected to logic 1.

TRUTH TABLE

PIN CONNECTIONS PIN 1 Input B Connected to Output B of 4029 (Pin 11) PIN 2 Input C Connected to Output C of 4029 (Pin 14) PIN 3 Lamp test Connected to +Vcc PIN 4 Blank out Open PIN 5 Blank Input +Vcc PIN 6 Input D Connected to Output D of 4029 (Pin 2) PIN 7 Input A Connected to Output A of 4029 (Pin 6) PIN 8 Ground PIN 9 e Connected to Pin 1 of Led Display PIN 10 d Connected to Pin 2 of Led Display PIN 11 c Connected to Pin 4 of Led Display PIN 12 b Connected to Pin 6 of Led Display PIN 13 a Connected to Pin 7 of Led Display PIN 14 g Connected to Pin 10 of Led Display PIN 15 f Connected to Pin 9 of Led Display PIN 16 +Vcc

LETS COMPLETE THE DIGITAL CLOCK…

THANK YOU…!!!