140 likes | 292 Views
Rd 3 - Electronics. Ohm’s Law Potential Divider Resistor in Series and Parallel - Application of Ohm’s Law 4. Switches and Relay. Darlington Pair.
E N D
Rd 3 - Electronics • Ohm’s Law • Potential Divider • 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 DarlingtonPair) 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? • It is much more sensitive • The TIP121 is a form of Darlington pair and can carry up to 1 amp of current. Most transistors carry 100mA • Only a tiny base current is needed as the gain is around 1000 • Note however that this transistor switches at 1.2V Why?
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
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.
T b T a P 1 P 2