mini project lab manual

7/22/2019 Mini Project Lab Manual

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Trinity college of Engineering

TOUCH SWITCH/PLATE

Introduction

The kit combines a touch switch and a touch plate all together in the same kit. Inthe touch switch two leads must be shorted together by your finger touching them. In the

touch plate one plate needs to be touched. The touch switch only needs a battery to activate it

but the touch plate requires a main power supply. A relay rated at 240V is included with the kit

so that you may use to switch light or other mains appliances. To use the relay you must use a

12V supply taken from the main power supply.

The use of the relay to switch 220V supply with this project must use the correct

boxes and connectors to protect us. The kit is constructed on a single sided printed circuit

board (PCB). A computer aided design programme is used to design the board.

CIRCUIT DIAGRAM

CIRCUIT DESCRIPTION

The main part of the circuit are the two NAND gates of the 4011 IC which are connected as a

flip-flop. Pins 9 and 13 are the ON and OFF contacts. The two gates are connected to the

positive rail by the two 10M resistors. Shorting one of the gates with the ground rail by

touching it (this is equivalent to connecting about 50K between gate and ground) FLIPs the

output to that state. Shorting out the other contact FLOPs it back again. The output of the flip-

flop drives a transistor connected as a switch. It switches an LED and a relay. The relay is rated

to switch 240V. Connecting the two 1K resistors connects the other two NAND gates of the IC

into the flip-flop and makes it much more sensitive with all four gates connected as flip flop.


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The touch switch works by capacitive pickups to the mains hum. When the contact is touched

body capacitance picking up general RF in the air is enough to short the plate to ground.

Because the touch plate uses mains hum as it method of shorting the gate to ground a mains

connected power supply must be used to supply power to the switch. A battery will not work.

The 4011 is a quad (4 of), 2 input, NAND gate.

PARTS LIST

Resistors

R1, 2, 3 - 1K

R4, 5 - 10M

Semiconductors

D1 -1N 4002

IC1 -4011/14011

Tr1 -BC 557

Miscellaneous

12V Relay1No

14 pin IC socket1No.

5mm LED1No

The kit introduces the 4011 IC. Go through the connections of the IC to determine the

LOW/HIGH levels as the OFF and ON plates are touched. Notice how connecting the two 1K

resistors increases the sensitivity of the circuit.


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DANCING LIGHT/SOUND LEVEL INDICATOR

INTRODUCTION

Here is a simple circuit that can be used for dancing lights or as a sound level

indicator. Most of the record player amplifiers, stereo systems or cassette decks etc. that are

available a few years ago had no such indicators as it was a costly affair. The circuit described

here costs around Rs.50/- and can be installed easily.

CIRCUIT DIAGRAM

CIRCUIT DESCRIPTION

Transistor TI amplifies the signal received through VR1 & C1 at the base of the transistor from

speaker terminals connected between points A & B. the 100k preset VR1 in series with coupling

capacitor C1 serves as the sensitivity control and can be set for the best response. Diode D1 is

used for providing polarity protection to the circuit, in case it is connected with reversed

polarity. R1 is the biasing resistance for T1. Capacitor C2 provides a bit of time delay to give

sufficient time for providing base voltage to transistor T2 and T7 so that they conduct & LEDs

connected at collectors to the transistors glow. Diode D2 to D7 provide base voltages along

with resistances R9 to R14.


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The values of resistors R9 to R14 are chosen in such a way that transistors T2 to T7

conduct in sequence, which the level of sound increases at the maximum sound level, T7 will

conduct while at lower levels it will remain inactive. Diode D2 to D7 ensure unidirectional base

voltages to transistors T2 to T7 for good response. D8 to d14 are LEDs with current limiting

resistance R2 to R8 of 1K, watt each. D8 is Zero sound level LED, which starts glowing assoon as the system is switched on.

Two similar circuits can be assembled in small veroboards of 7.5cm*5cm

for the two channels of a stereo system.

PART LIST

RESISTORS

R1, 10 -4.7K, R2,3,4,5 - 1K

R6, 7,81K, R92.2K

R116.8K, R1210K

R1318K

R1422K

VR1100K

CAPACITORS

C1100UF/10V

C2220UF/16V

SEMICONDUCTORS

T1BC 158B

T28 BC 148

D17 - IN 4001

D8.14 LED


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LED DANCING LIGHT (9V)

INTRODUCTION

There are many ways to attract people by wearing colored clothes or by different

hair styles etc. Here is novel idea to attract others towards you. The circuit given below is

nothing but simple multivibrator using transistors.

CIRCUIT DIAGRAM

The LEDs are connected to collector of each transistor thus they glow alternatively. PCB is easy

to construct within couple of minutes.

Parts list

R1, R356K

R2, R4100E

Capacitors

C1, 2- 100uf/16V or 4.7uf/16V

Semiconductors

T1,2BC148

LED Red- 3

LED green- 3


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WATER LEVEL INDICATOR

Introduction

This simple circuit gives an audio visual indication when the overhead tank fills.

The buzzer beeps and LED blinks when the sensor touch pads makes contact through water.

CIRCUIT DIAGRAM

Normally the touch pads are free so that the reset pin 12 of IC1 will be high (as set by VR1).This

inhibits the oscillation of IC. IC CD4060 is used as the timer with the timing components C1 and

VR2. IC oscillates when its reset pins 12 turns low. So normally the output of IC1 will be low and

the LED and buzzer remain off. When the water level increases and makes contact with the

touch pads, it shorts and the reset pin 12 of IC1 will turns low. This initiates the oscillation of IC

and the buzzer sounds along with the blinking of LED.


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MUSICAL BURGLAR ALARM

mini project lab manual

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