## Thursday, May 26, 2011

### Sound-Activated Switch using Op amp 741

Sound activated switch shows how to make an

*reference voltage of 0 to 100V. We use a 10 kΩ pot, 5 kΩ resistor, and +15V supply to generate a convenient large adjustable voltage of 0 to 10V. Next we connect a 100:1***adjustable***that divides the 0 to 10V adjustment down to the desired 0 to 100mV adjustment reference voltage. Again, signal source E***voltage divider**_{i}is used as a microphone and an alarm circuit is connected to the output. With this sound-activated switch, control by sound may be very useful in different ways. For example, a sound-activated light responding to a knock on the door or a

*. The light will be***hand clap***switched off after a few seconds. Actually, the practical application that uses a positive level detector is the sound-activated switch shown in Figure.***automatically** Any noise signal will generate an ac voltage and

*e is used as an input. The first positive swing of***microphon**__of E__*Op amp*_{i}above V_{ref}drives V_{o}to +V_{sat}. The diode now conducts a current pulse of 1 mA into the gate, G, of the silicon-controlled rectifier (SCR). Normally, the SCR’s anode, A, and cathode, K, terminals act like an open switch.Fig: A sound-activated switch is made by connecting the output of a non-inverting voltage-level detector to an alarm circuit.

However, the gate current pulse makes the

*turn on, and now the anode and cathode terminals act like a closed switch. The audible or***SCR***is now activated. Furthermore, the alarm stays on because once SCR has been turned on, it stays on until its anode-cathode circuit is opened.***visual alarm** The circuit of Figure can be modified to

The strobe does the work of apparently stopping the bullet in midair. If we close the shutter, the position of the

*high-speed events such as a bullet penetrating a glass bulb. Some cameras have mechanical switch contacts that close to activate a stroboscopic flash. To build this sound-activated flash circuit, remove the alarm and connect anode and cathode terminals to the strobe input in place of the camera switch. If we open the***photograph***and fire the rifle at the glass bulb, the rifle’s sound will activate the switch.***camera shutter**The strobe does the work of apparently stopping the bullet in midair. If we close the shutter, the position of the

*in relation to the bulb in the picture will adjusted experimentally by moving the microphone closer to or farther from the rifle.***bullet** We use sound activated switch circuit in different ways. For light activated relay switches,

**, sound activated***machine gun sounds**, sound effects generator electronic circuit, auction of test equipment and many other works we use this circuit. This sound activated switch circuit makes our activities easy and comfortable.***FM transmitter**### Smoke Detector

Small change of light the

*will be activating. Initially photo-conductor resistance shall have to high value. Total Circuit designing. Smoke Detector is a detector which is activating by the smoke. It is another practical application of a***smoke detector***. Smoke Detector is working with the change of voltage. This circuit can be used in***voltage-level detector***.***fire alarm** Smoke Detector of Figure the lamp and photo-conductive cell are in an enclosed chamber that admits smoke or dust but not external light. The photo-conductor is a light-sensitive resistor. In the absence of smoke or dust, very little strikes the photo-conductor and its resistance stays at some high value, typically several hundred kilohms. The 10-kΩ

*control is adjusted until the alarm turns off.***sensitivity** Any particles entering the chamber cause light to reflect off the particles and strike the photo-conductor. This, in turn, causes the photo-conductor resistance to decrease and the voltage across R1 to increase. As E

_{i }increases above V_{ref}, V_{o}switches from –V_{sat}to +V_{sat}, causing the alarm to sound. In initial condition

*resistance must contain high resistance otherwise the detector will be always activated. When the voltage of inverting terminal and non-inverting terminal are same output show 0 V.***photoconductor** Output voltages not more then supply voltage. The resistive network at the input of the op-amp forms a

*. This circuit can be used to monitor the level of dust particles in a clean room.***Wheatstone bridge**### Integrator Circuit Using Op amp 741

An integrator is a circuit which shows the sum of input voltage at the output. That means it works by the operation of integral form. If we see the output of the integrator shows the

*of input voltages, the result of***summation***circuit will be right. Such that, if we give square wave at the input, then we will get triangular wave at the output.***integrator** A circuit in which the output voltage waveform of

*is the integral of the input voltage waveform is the integrator or the integrator amplifier. Such a circuit is obtained by using a basic inverting amplifier***Op amp***if the feedback resistor R***configuration**_{F}is replaced by a capacitor C_{F}. Integrators are used in the design of signal generators and signal processing circuits. It is also used in analog computers and analog-to-digital (ADC) and signal-wave

**shaping circuit****.***s* When V

_{in}= 0, the integrator of Fig 1(a) works as an open-loop*. This is because the capacitor C***amplifier**_{F}acts as an open circuit (X_{CF}= ∞) to the input*V***offset voltage**_{io}. In other words, the input offset voltage V_{io}and the part of the input current charging capacitor C_{F}produce the error voltage at the output of the integrator. Therefore, in the practical integrator to reduce the error voltage at the output, a resistor R

_{F}is connected across the*capacitor C***feedback**_{F}. Thus, R_{F}limits the low-frequency gain and hence minimizes the variations in the output voltage. Both the

*and the low-frequency roll-off problems can be created in ideal integrator. Those problems can be corrected by the addition of a resistor R***stability**_{F}. From the*result, we can see that the output of square wave is the triangular wave. So, we can say that integrator does the sum at the output.***simulation**### Design a Subtractor

A basic differential amplifier can be used as a sub-tractor. We can get the difference of two input voltages in the output of op-amp as output voltage. The circuit diagram of a basic

*amplifier is drawn below.***differential** This is a linear

*network. So, applying super position theorem, we can find the output voltage equation.***bilateral**Let, assume that only Va is applied and Vb is short.

### Voltage to current converter with floating load

The current in the feedback loop depends on the voltage and

*Ri.*This applications where we need to pass a constant current through a load and hold it constant despite any changes in load resistance or load voltage. When the load does not have to be grounded, we simply place the load in the*loop and control both input and load current from this circuit.***feedback**This circuit shown in figure voltage to current

*with floating load. The voltage to current converter can be used in such applications as low voltage dc and a voltmeters, diode match finders light emitting diodes (LEDS) and***converter***.***zener diode tester** This circuit diagram Figure shows a voltage to current converter in which load resistor

*R*is floating (not connected to ground). The input voltage is applied to the no inverting input terminal and the feedback voltage cross_{L}*R*drives the inverting input terminal. This circuit is also called a current series_{1}*amplifier because the feedback voltage across***negative feedback***R*(applied to the inverting terminal) depends on the output current_{1}*i*and is in series with the input difference voltage v_{0}_{id}.## Wednesday, May 25, 2011

### First Order Low Pass Filter

Here an explanation of the operation of low pass filter was made, the operation principle of active low pass filter was made, of active low pass filter was made, I designed an active low pass filter & finally I have drawn the

*of designed active filter by using filter gain equation & plotting the frequency vs. gain curve.***frequency response**An electric filter is

*circuit that passes a specified band of frequencies & blocks or attenuates signals of frequencies outside this band. Active filters can be designed using op-amps, resistors, capacitors or inductors.***frequency-selective***are used for audio or low frequency operation, where LC filters are used for high frequencies. For designing audio filters I used capacitors, because inductors are very large, costly & may dissipate more power. I chose active filters instead of passive filters because,***RC filters**a. It has gain & frequency adjustment flexibility.

b. It has no loading problem.

c. It has very high input impedance & very low output impedance.

d. It is more economical than passive filters.

I designed first order low pass

*filter with RC network in my present assignment. The key characteristic of butter-worth filter is it has a flat pass-band & a flat stop-band. The ideal and practical frequency response of a first order low pass filter is given below,***butter-worth**The above figure shows the frequency response of a 1

^{st}order low pass butter-worth*. The ideal frequency response is shown by the dashes line while the practical response is shown by the solid line. We can see from the frequency response that, the filter allow signal with frequencies less than f***filter**_{H}to pass through it & the signal appears at the output with predefined gain.Ideally it

*the signal appearing at the input which has frequencies greater than f***attenuates**_{H}& gives zero output. Ideally at f_{H}, the frequency response curve changes sharply from A_{F}(closed loop gain) to zero. Hence the frequencies from f to f_{H}are called pass-band frequencies & frequencies greater than f_{H}are called stop-band frequencies.f

_{H }is called high*. Unfortunately the change is not so sharp at f***cutoff frequency**_{H}in practical low pass filters. In practical 1^{st}order low pass butter-worth filter gain changes with 20dB/decade with frequencies greater than f_{H}.### Third-Order High-Pass Filter

This report focuses on active third-order high-pass

*design using***filter***amplifiers. High-pass filters are commonly used to implement high frequency in a system. Design of Third-order filters is the main topic of consideration. To illustrate an actual circuit implementation, separated into two types of filters***operational***and second-order.***first-order** A third-order high pass filter is formed by connecting in series first and second order high pass section and so on. As the order of the filter increased, the actual stop-band

*response*of the filter approaches its ideal stop-band characteristic. The overall gain of the filter is fixed because all the frequency determining resistors and capacitor are equal. A filter is a device that passes electric signals at certain frequencies or

*while preventing the passage of others. High Pass Filter (HPF), sometimes called a low-cut filter, is a filter that high frequencies can be transmitted well and frequencies lower than the cutoff frequency are attenuated or reduced. The actual amount of***frequency ranges***attenuation*for a particular frequency varies from filter to filter. A third-order high pass filter is formed by connecting in series first and second order high pass section and so on. In the stop-band the gain of the filter changes at the rate of 20 dB/decade for first-order filter and at 40 dB/decade for second-order filter. This means that, as the order of the filter is increased, the actual stop-band response of the filter approaches its ideal stop band characteristic.

Higher order filter are formed simply by using the first and second order filter. A third-order high pass filter is formed by connecting in series first and second order high pass section and so on. Although there is no limit to the order of the filter that can be formed, as the order of the filter increase, so does its size.

Also, its accuracy declines, in that the difference between the actual stop-band

*and the theoretical stop-band response increase with an increase in the order of the filter. Note that in the third order filter the voltage gain of the first order section is one, and that of the second order section is two. This gain values are necessary to guarantee***response***butter-worth*response and must remain the same regardless of the filter’s cutoff frequency. Furthermore, the overall gain of the filter is fixed because all the frequency determining resistors and capacitor are equal. Generally, the minimum-order

*required depends on the application specifications. Although a higher-order filter than necessary gives a better stop-band response, the higher-order type filter is more complex, occupies more space, and is more expensive. As the order of the filter increased, the actual stop-band response of the filter approaches its ideal stop-band***filter***.***characteristic**
Labels:
attenuation,
butter-worth,
Circuit diagrams,
cutoff frequency,
filtered,
first-order,
frequency range,
Hobby Electronics,
Hobby electronics projects,
operational amplifier,
response,
stop-band

### First-Order Band-Pass Filter

Application of first order band pass filter to find out the output voltage gain magnitude of specific

*. A specific range of frequency can pass through the***frequency***which has a specific bandwidth of this band pass filter.***amplifier**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*_{H}_{ }and*f*such that_{L}*f*_{H}_{ }>*f*. Any input frequency outside this pass band is_{L}*. 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.***attenuated**The relationship between Q, the 3-dB

*and the center frequency*

**bandwidth***f*is given by,

_{c }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

*of the high pass and low pass filters.*

**gain magnitudes**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

*filter was designed by taking following precautions,***band width**a.

Limited magnitude of input voltage was applied at the input, so that the

Limited magnitude of input voltage was applied at the input, so that the

*must not be driven to saturation.***op-amp**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.

### Electric Analog Computation

*is one of the basic concepts in the field of modern electronic computing. In electronic analog computation any equation can be solved by using some analog circuits which is designed by using op-amps .In my assignment I try to present the concept of electronic analog computation by solving a differential equation with a correspondent circuit .*

**analog computation** Electronic analog computation is such kind of electronic computation in which basic analog computing elements such as adders ,

In this a differential equation is solved by electronic analog computation.*,multipliers,***integrators***etc are used to solve any desired equation such as differential equations etc .It is the basic concepts of analog computer.***comparators** Let a differential equation be :

^{ }

^{ }D

^{2}v+k

_{1}Dv+k

_{2}v-v

_{1}=0……………….(1) Where, k

_{1}and k

_{2}are constant terms.

In the starting I assumed that D

^{2}v is available in the form of a voltage .Then by means of an*I will get the voltage proportional to Dv. A second integrator gives the voltage proportional to v .Then an adder gives –( k***integrator**_{1}Dv+k_{2}v-v_{1}) From the equation it is equal to D^{2}vand hence the output of this summing

*is fed to the input terminal ,where I had assumed that D***amplifier**^{2}v was available in the first place. The integrator 1 has a

**time constant***RC*=1s, and hence its output at terminal 1 is –Dv .This voltage is fed to a similar integrator 2 and the voltage at terminal 2 is +v. The voltage at terminal 1 is fed to summing amplifier 1 which gain is 1 and in the output terminal 3 I get + k_{1}Dv- v_{1.} where k

_{1}=(R/R_{1}).At the end the output of terminal 2 and 3 are fed to summing amplifier 2,from where I will get^{ }D^{2}v= - (k_{1}Dv+k_{2}v-v_{1}) at terminal 4.Fig1.1: Electronic analog computing circuit for calculating a differential equation .

*.But we have to careful to set the gain of the circuits because in some steps the constant term of the equation is represent by the*

**op-amp***of the correspondent circuit .So, we have to design the circuits according to gain which represents the constant term*

**gain**### Design a Temperature Indicator

This circuit is a

**circuit or differential***temperature indicator**amplifier using a transducer bridge. This circuit is calibrate in degrees Celsius or Fahrenheit. In the circuit used buffer in and points for exact voltage of and points. Because gain is always 1 of buffer circuit. Then the output voltage of***instrumentation****is input voltage of differential amplifier.***buffers*The differential amplifier is difference voltage of and points using

**. When temperature is increased then resistance is also decreased and output voltage is decreases and when temperature is decreased then resistance is also increased and output voltage is increases.***741*__Op Amp__ The temperature indicator is a circuit that indicates of temperature in degrees Celsius or Fahrenheit. The temperature is inversely proportional to the resistance or

*.***transducer***or temperature is connected in one arm of the bridge with a small circle around it and is denoted by , where is the resistance of the*

**physical energy***and is the change in resistance.*

**transducer**Fig.01 - Temperature indicator

In the circuit used as the transducer in the bridge circuit is a thermistor and replaced output voltmeter to temperature indicating meter. Then temperature indicating meter is

*in degrees Celsius or Fahrenheit.***calibrate**The bridge can be balanced at a desired reference condition, for instance 25

^{0}C. As the temperature varies from its reference value, the resistance of the*changes and the bridge become unbalanced. This unbalance bridge in turn produces the meter movement.***thermistor**### Analog weight Scale

The most common

*implementation is to use a transducer bridge, with voltage output directly proportional to the weight placed on it. The trend in weight scales towards higher accuracy and lower cost has produced an increased demand for high-performance analog***weight-scale***processing at low cost.By connecting a strain Gage in the bridge ,the differential***signal***amplifier can be converted in to a simple analog weight scale.***instrumentation** In the analog weight scale, strain Gage elements are connected in all four arms of the bridge. The elements are mounted on the base of the

*platform, so that, when an external force or weight is applied to the platform, one pair of elements in the opposite arms elongates, whereas the other pair of elements in the opposite arms compresses.***weight** On the other hand, When no weight is placed on the platform, the bridge is unbalanced, R

_{T1}=R_{T2}=R_{T3}=R_{T4}=R, and the output voltage of the weight scale can be zero. When a weight is placed on the scale platform, the bridge becomes*. In other words, when the weight is placed on the platform, R***unbalanced**_{T1}and R_{T3}both decrease in resistance and R_{T2}and R_{T4 }both increase in resistance (Figure 01).The analog weighing measuring scales need to be hung properly before we start measuring anything using the same. They never allow measuring the weight of anything that we want as they have some limitations. If we think about measuring anything using an

One thing we need to keep in our mind while using such a scale is the limitation, if we load anything which weights more than the mentioned limit by the

*scale we need to check the analog lines to get the nearby accurate measurement.***analog**One thing we need to keep in our mind while using such a scale is the limitation, if we load anything which weights more than the mentioned limit by the

*of the scale we may end up damaging the same. Analog scales were never capable of providing accurate weight of any item and at the same time, it involves human effort to measure anything where the chances of human error are quite normal***manufacturer**For better accuracy, a

*-based digital weight scale may be constructed.But it is much more complex and expensive than the analog scale.*

**microprocessor**### The Differential Input and Differential Output

For getting balanced

*output we use this circuit. In this circuit two source is present, so the superposition theory is applied to get the output. In this circuit both the inverting and non-inverting terminal is working.It rejects the common-mode voltages, so it is very useful in noisy environments.***differential**A differential input and differential output amplifier using two identical

__. It is most commonly used as a preamplifier and driving__*Op amp**arrangement. The differential input and output are inphase or the same polarity provided***push-pull***V*and_{in }=V_{x}– V_{y}*V*

_{o }=V_{ox}– V_{oy }When we want to find out the 1

^{st}op-amps output*V*, we will use the superposition theory._{OX}When we get

*V*is active ,_{X }*V*is inactive then ,_{Y }In non inverting terminal

*V*

_{1}= (1+*)V*

_{X}When we get

*V*is active,_{y }*V*is inactive then,_{x }In inverting terminal,

*V*

_{1 }= -*V*

_{y} So

*, V*_{ox}= V_{1}+V_{1}

_{ }*=(1+*

*)V*

_{X }-*V*

_{y}Fig: The circuit diagram of the differential input and output amplifier.

When we want to find out the 2

^{nd}op-amps output*V*,we will use superposition theory._{Oy} When we get

*V*_{X}_{ }is active ,*V*is inactive then_{Y } In inverting terminal ,

*V*

_{2}= -*V*

_{x} Again, when we get

*V*is active ,_{y }*V*is inactive then_{x } In non inverting terminal we get,

*V*

_{2}= (1+*)V*

_{y}So,

*V*_{oy}= V_{2}+V_{2}*=(1+*

*)V*

_{y}*-*

*V*

_{x}So the output result

*V*

_{o }=*V*

_{ox}– V_{oy}*= (1+*

*)V*

_{X }-*V*

_{y }*–[(1+*

*)V*

_{y}*-*

*V*

_{x }]*=*

*(1+*

*) ( V*

_{X }- V_{y }) +*( V*

_{X }- V_{y })*= ( V*

_{X }- V_{y })*(1+*

*)*

**Design**

To design a input and differential output amplifier,

*taking a differential output of at least 3.7**V*and the differential input*V*_{in }=10V. We know,

*V*

_{o}= ( V_{X }- V_{y })*(1+*

*)*

Or,

*3.7 = (0.1)**(1+**)**Or,*

*37 =*

*(1+*

*)*

*Or,*

*36 =*

*Or,*

*R*

_{f }= 18 R_{1} Let

*, R*then_{1}= 100Ώ,*R*_{f }= 1.8 KΏ .

_{ }
Subscribe to:
Posts (Atom)