Wiring Diagram

Showing posts with label 3-dB bandwidth. Show all posts

Wednesday, June 15, 2011

Remote Control Using the NE 555 and LM 567

Remote control circuit consists of two parts, one is transmitter and the other is receiver. A simple diagram is schematic remote control. The transmitter circuit’s transmitter IC is controlled by NE555. Receiver circuit works by the signal emitted frequency which is emitted by that transmitter circuit. Transmitted signal frequency must be equal to the frequency decoder of the receiver circuit. The NE 555 generated frequency is same that receive frequency of IC LM 567.

The output frequency of the transmitter circuit is f,

f = 1.44/(Ra+2Rb)C

The resistor R1 is a receiver variable to facilitate the process of tuning. The system works well when the circuit is ready. The first step is tuning by way of the transmitter is turned on continuously, while the receiver R1 to set the value to be able to detect the signal transmitter. The second part is the receiver is controlled by LM 567. The following is a schematic drawing recipient.

f = 1 / (1.1 xR1xC1)

This frequency depends on the value of R₁ and C₁.

In the picture on top of each channel is designed with a different frequency. By considering the bandwidth of the frequency detection signal LM 567, inter-frequency channels should have a big enough difference, let’s try with a difference of 5 KHz.

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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 f_Hand f_L such that f_H> f_L. 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 f_cis 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.

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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