basic home appliance

8/8/2019 Basic Home Appliance

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BASIC HOME APPLIANCE



Agenda

Electric Bulb

Halogen Lamp

Tube Light Mini Emergency Light

Mini Tester



Electric Bulb



Electric bulb



A halogen lamp



Tube light

A fluorescent light contains a mercury vapor that gives off ultraviolet light

when ionized.

When voltage is applied to the fluorescent lamp

1. The starter allows current to flow through the filaments at the ends of the tube.

2. The current causes the starter's contacts to heat up and open, thus interrupting theflow of current. The tube lights.

3. Since the lighted fluorescent tube has a low resistance, the ballast now serves as a

current limiter



Tube light

When you turn on a fluorescent tube

a. the starter is a closed switch

b. The filaments at the ends of the tube are heated by electricity, and

they create a cloud of electrons inside the tube

c. The fluorescent starter is a time-delay switch that opens after a

second or two. When it opens, the voltage across the tube allows a

stream of electrons to flow across the tube and ionize the mercury

vapor

Without the starter, a steady stream of electrons is never

created between the two filaments, and the lamp flickers

Without the ballast, the arc is a short circuit between the

filaments, and this short circuit contains a lot of current. The

current either vaporizes the filaments or causes the bulb to

explode.



Start Behaviour of Fluorescent Lamps

Test circuit for measuring behavior of the

starting TL.



During the startup of a TL the following distinct

phases can been distinguished:

a. The voltage on the TL circuit is present, but the current and the power are

very small.

b. The current is low, as well as the power. This can been observed by the

slight increase of the energy line.c. The power is primarily reactive. Despite that the power amplitude is

large, the energy use of this part is relatively low.

d. The current and power amplitiude are now lower than during the ignition

phase C, but because the circuit now has a more ohmic character, the TL

use more energy. Note that te power curve now is asymetrical around thezero-line.

The measurement shows clearly that during the normal working

the energy line is the steepest and therefore the most energy

is used. The startup requires a relatively low power.



Mini Emergency light



Components Required

Resistors

± R1, R2 (200 Kilo ohms -

1W)

±R3 (100 Kilo ohms -1/2W)

± R4 (100 Kilo ohms -

1/2W)

Diode ± D1 (IN 4001)

Capacitor

± C1 (0.1MF - 50V)

Transistors

± T1 (BC148B)

± T2 (SL100)

Miscellaneous

± Battery, Dry cell -1.5V

± Bulb -3V

± PCB or Breadboard

± Flexible Wire

± Soldering rod etc..



P rinciple and Working

This is a very simple emergency light experiment; advantage of this circuit

is that the bulb glows automatically as soon as the AC supply goes off.

If AC supply is present, the alternating voltage is passed through diodeD1.

D1 behaves as a half wave rectifier and lets only positive voltage to passon. This positive voltage charges capacitor C1 to a voltage much greater

than battery voltage. This condition puts both T1 and T2 in reversed bias,

resulting in no current through both the transistor, and keeping the bulb

off.

When AC supply goes off, capacitor C1 discharges through R3. Due to thisdischarging of C1, voltage across C1 decreases gradually. The point when

capacitor voltage goes below battery voltage, transistor T1 goes in to

forward bias making transistor T2 also in forward bias. Now since both the

transistors are in forward bias they provide enough current to flow from

bulb, and the bulb glows.



Mini Tester



Components Required

Resistors

± R1 (68 kilo ohms , 1/2W)

± R2 (330 kilo ohms , 1/2W)

± R3 (1 kilo ohms, 1/2W)

± R4 (680 ohms, 1/2W)

± R5 (22 ohms, 1/2W)

Transistors

± T1 (BC107)

±T2 (AC128 or AC188)

LED

± LED1

Miscellaneous

± Battery, Dry cell 6V

± (L1, L2) Testing probes or

crocodile clips

± S1 ( Slide switch, single pole)

± PCB or Breadboard

± FlexibleWire

± Soldering rod etc..



Continuity Testing : Connect the two probes to the points between which

the continuity has to be tested. If the LED glows! the points are electrically

continuous otherwise not.

Resistor Testing : This circuit can test upto 10K resistors. If LED glows,

resistor is good otherwise faulty.

Capacitor Testing : When a electrolytic capacitors is put in between L1 and

L2 the LED should show glow momentarily. If the LED glows continuous,

the capacitor is defective.

Diode Testing : A good diode will produce a glow in one direction only. If a

diode produced glow in both directions, or in none of the direction, diode

is faulty.

Transformer coil Testing : A good transformer winding should glow LED,

but in case of "open circuited" faulty coil, the LED won't glow.

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