Tuesday, August 30, 2011

Luggage Protector Circuit Using 555 Timer IC

The circuit is called protector alarm circuit to protect from the theft of your luggage or bags. This circuit is built electronically using 555 timer IC. The alarm will rise highly when the thin wire is cut off by the thief.  The circuit configuration using 555 timer IC acts as a astable multivibrator which produce signal tone of frequency of about 1 KHz and produce sound like a shrill noise away the output speaker.

If you need to know 555 Timer configuration click here and download
IC’s 5number pin is directly connected to the power supply. 10k, 68k resistor and 0.01uf capacitor are connected to generate specific range of frequency like as 1KHz. You can change output frequency by changing the value of  resistor and capacitor.  Pin 1 is directly connected to the ground. Output is taken from pin 3. A 8Ohms speaker is connected to the output for alarm sound. Thin wire is connected as shown in figure.
The wire would be very thin copper like 36 SWG or higher. You can use one gage of normal wire. The driving voltage of the circuit is 5 Volt to 12 Volt.

Monday, August 29, 2011

Transistor AM Modulator Circuit Diagram

Modulation is the process of changing some characteristics (e.g. amplitude, frequency or phase) of a carrier wave in accordance with the intensity of the signal is known as modulation.

The figure shows the electronics circuit of a simple am modulator. It is essentially a CE amplifier having a voltage gain of A. The carrier signal is the input to the amplifier. The modulating signal is applied in the emitter resistance circuit. 

The carrier ec is applied at the input of the amplifier and the modulating signal es is applied in the emitter resistance circuit. The amplifier circuit amplifies the carrier by a factor A, so that the output is Aes. Since the modulating signal is a part of the biasing circuit, it products low frequency variations in the emitter circuit. This in turn causes variations in “A”.

The result is that amplitude of the carrier varies in accordance with the strength of the signal. Consequently, amplitude modulated output is obtained across RL. It may be noted that carrier should not influence the voltage gain A; only the modulating signal should do this. To achieve this objective, carries should have a small magnitude and signal should have a large magnitude.

Wednesday, August 17, 2011

A.M Modulator Circuit Diagram

Amplitude modulation is a process in which the amplitude of a carrier wave c(t) is varied about a mean value, linearly with the base-band signal m(t).
In amplitude modulation the amplitude of a high-frequency carrier is varied in direct proportion to the low-frequency (base-band) message signal. The carrier is usually a sinusoidal waveform that is,
C(t) = Ac . cos(wt)
Where,  is the carrier amplitude and fc is the carrier frequency.
The base-band signal or message signal is,
m(t) = Am . cos(wt) 
Where, Am is the amplitude of message signal and fm is the frequency of message signal.
An amplitude modulation wave may thus be described in its most general form as the function of the time as follows,
S(t) = m(t)×c(t)

Friday, August 12, 2011

Mini Auto Charger Fan Circuit

This circuit is called the auto circuit which can use any electronic device to operate it automatically. To make this circuit the cost is very low. Any interested student can make it very easily. The main component of this circuit is transistor. Its operation is very easy. 

The main purpose of this is to operate a charger fan where need 6volt battery. This circuit is mainly needed when the main power is OFF. That is called load shedding. Because at the time of  load shedding , 6volt battery operate the fan automatically. You don’t have need to ON the switch of the fan or OFF the fan switch. Only relay work this as a switch. The charging system is also automatically. On the other big matter is that no over charge is occurred of the battery. So the life time of the battery is increased. 

1.      Transistor ( npn ) – 2N2222, BC547
2.      Zener Diode - 6.8V
3.      Diode
4.       Relay - 6V
5.      Resistor – 1K, 100Ω
6.      Rechargeable Battery - 6V
7.      Fan - 6V
8.      Power supply - 6V

This circuit is three section, input section and output section. 2N2222 transistor is used to control relay. BC547 transistor is used to control output section using relay. Zener diode and a diode connect with BC547 transistor base as a series connection. Zener diode always controls battery charge. It zener voltage is 6.8V which can’t overcome battery voltage.
When power supply voltage is applied to the 2N2222 transistor base the transistor is on. So the relay is ON relatively the output circuit is OFF. Inverse will occurs when power supply voltage is OFF. When 2N2222 transistor is ON then relay active only battery charging, relay deactivate the fan. Zener diode always keeps battery voltage full (6volt).
1.      Need not switch ON/OFF.
2.      It depends on AC power supply come or gone.
3.      This circuit is used when you are sleeping.
4.      Easy to make
5.      Cost is very low
6.      Components are few.
7.      Battery can’t over charge.
8.      Overall efficiency is 78%.
9.      Not you, only relay can do your work.
10.  The circuit is a small project for all students.