Rd 3 - Electronics

tweetbazaarElectronics - Devices

Nov 2, 2013 (3 years and 7 months ago)

60 views

Rd 3
-

Electronics

1.
Ohm’s Law


2.
Potential Divider


3.
Resistor in Series and Parallel



-

Application of Ohm’s Law


4. Operational Amplifier (Comparator and Gain)


5. Switches and Relay



9V Battery

1 SPDT Switch

Thermistor

Variable Resistor

10K Resistor (*3)

3140 Op_amp

TIP121 Transistor

IN4148 Diode

M66T Music IC

8 Ohm Speaker

3V Battery
Connector

1 SPDT Relay

220uF Capacitor


Using Operational Amplifier to control Music IC


9 Volt Circuit


3 Volt Music IC

3140 Op
-
Amp

An integrated circuit consisting of a silicon chip in a plastic 8 pin package

Contains 20 transistors eleven resistors and one capacitor.

Typical uses:
-

Voltage comparator, High gain amplifier

Circuit Symbol

Op
-
Amp as a Comparator

Compares the voltage at pin 2 to the voltage at pin 3



If V3 > V2 the output is high (on)


If V3 < V2 the output is low (off)


Voltage at pin 2 = threshold or reference voltage

Operational Amplifier Controlling Music IC

Darlington Pair

A special arrangement of two
transistors (often called a
Darlington

Pair
) is shown in the diagram
opposite. There are number of
situations in which we might make use
this configuration.

What are the advantage of using an
arrangement such as this?

(1)

It is much more sensitive

(2)

The
TIP121

is a form of Darlington pair and can carry up to
1 amp of current. Most transistors carry 100mA

(3)

Only a tiny base current is needed as the gain is around 1000

(4)

Note however that this transistor switches at 1.2V Why?


Curtain Controller

9 Volt Battery Clip

3V Battery Clip

3 Terminal Blocks

1k resistor

BC337 Transistor

1N4148 Diode

Red LED

470 Ohm Resistor

1 DPDT relay

1 Toggle Switch

1 SPST Switch

2 Microswitches

Motor


Potential Divider


DPDT motor control (Reversal)

Potential Divider

Turn 0n Voltage for a Transistor

Variable Resistor

Variable resistors consist of a
resistance
material

with
connections at both ends and a
wiper

which moves along the
track as the arm is rotated
through 270
°
.

The track is normally rotary but
straight track versions, usually
called
sliders
, are sometimes
used.

The further
clockwise

the wiper
is rotated, the larger the
resistance.

Dark sensor

Moisture Sensor

Heat Sensor

Heat Sensor


Hot or Cold

P 1

P 2

T b

T a