Showing posts with label audio frequency. Show all posts
Showing posts with label audio frequency. Show all posts
Friday, November 2, 2012
Freeze Protector Circuit
This is the simple freeze protector circuit diagram. It is also called timing circuit. It is just hobby project for beginners. When you need to operate automatically any device in the fixed time later after coming AC power supply, you can use this circuit.
The voltage amplitude
is high when AC power come. Suddenly high voltage destroys the
electronics device. For this reason, in the time of load shedding we
need to switched off electronics device (Audio/Video player, CD/DVD
Player, TV, Freeze or any electronics device). This circuit solve this problem.
Hobby Electronics helps the beginners to know the timing circuit specially using 555 IC
timer. NE555 IC is the very simple well known parts. Its configuration
is very simple. You can use this timer any simple circuit.
In this circuit use 12volt
power supplies. 300k variable resistor is used for timing control.
Timing resistor and capacitor are 300k and 1000uF. Only change the value
of the variable resistor for your required timing.
The circuit output pin 3 is connected with resistor (10k) and output 12 volt relay. Relay is connected as figured with the device. Making cost is too low. Anyone can make this circuit easily.
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, May 25, 2011
First-Order Band-Pass Filter
Application of first order band pass filter to find out the output voltage gain magnitude of specific frequency. A specific range of frequency can pass through the amplifier which has a specific bandwidth of this band pass filter.
A band pass filter is a frequency selector. It allows one to select or pass only one particular band of frequencies from all other frequencies that may be present in a circuit. This type of filter has a maximum gain at a resonant frequency.
A band pass filter is the combination of high pass and low pass filter combination. It has a pass band between two cut off frequency fH and fL such that fH > fL. Any input frequency outside this pass band is attenuated. There are two types of band pass filters wide band pass and narrow band pass. If the quality factor Q < 10 and Q > 10 then it would be wide band pass and narrow band pass filter.
The relationship between Q, the 3-dB bandwidth and the center frequency fc is given by,
According to Figure 01 of band pass filter circuit, there are two sections. One is first order high pass section and other is low pass section.
For first order high pass section the output voltage equation is,
For first order low pass section the output voltage equation is,
Putting the value of first order high pass section output voltage from equation (1),
So the final voltage equation of first order band pass filter is,
The voltage gain magnitude of the band pass filter is equal to the product of the voltage gain magnitudes of the high pass and low pass filters.
Therefore the equation (2) is,
Where, = Total band pass gain
f = frequency of the input signal (Hz)
= low cut off frequency (Hz)
= high cut off frequency (Hz)
The above first order low pass band width filter was designed by taking following precautions,
a.
Limited magnitude of input voltage was applied at the input, so that the op-amp must not be driven to saturation.
Limited magnitude of input voltage was applied at the input, so that the op-amp must not be driven to saturation.
b. Only selected frequency can pass through the filter.
c. Overall gain of the first order band pass filter is the multiplication of high pass filter gain and low pass filter gain.
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