Download Presentation Sample Electronic Circuits (Round 3 - Professional

Rd 3 - Electronics
1. Ohm’s Law
2. Potential Divider
3. Resistor in Series and Parallel
- Application of Ohm’s Law
4. Switches and Relay
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
Potential Divider – DPDT motor control (Reversal)
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
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
Tb
Ta
P1
P2