Sunday, June 12, 2011
IR Remote Control Circuit using Op amp 741
IR circuit is called Infrared Circuit. Remote controls are very much popular now-a-days. It is specially called cordless circuit. This circuit is very simple and low cost cordless remote control circuit which is based on infrared rays.
Figure 1 shows the transmitter circuit. The transmitter produces infrared rays and that can be easily transmitted up to 4 meters with a special convex lens and a twin LED arrangements.
Figure 2 shows the receiver circuit. Op amp IC1-741 generates high frequency squire wave which provides the gate pulses for SCR1. IC1’s output current flows through SRC1 and it is conducting current and enables the LED to emits infrared rays. The output frequency of Op amp IC1 depends on the variable resistor VR1, which in turns varies the output radiations of the LED.
When IR rays fall on the photo-transistor T1 of the receiver, then base of the photo-transistor’s base produces charge carriers at a rate depending on the rate of arrival of incident radiations at the pn junction of the transistor. Then the resulting emitter voltage is amplified by Op amp IC-2 . The amplified signal is rectified by D2. Finally the amplified signal is to drive the relay.
Parts List:
Thursday, May 26, 2011
Sound-Activated Switch using Op amp 741
Sound activated switch shows how to make an adjustable 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 voltage divider that divides the 0 to 10V adjustment down to the desired 0 to 100mV adjustment reference voltage. Again, signal source Ei 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 hand clap. The light will be automatically switched off after a few seconds. Actually, the practical application that uses a positive level detector is the sound-activated switch shown in Figure.
Any noise signal will generate an ac voltage and microphone is used as an input. The first positive swing of Op amp of Ei above Vref drives Vo to +Vsat. 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 SCR turn on, and now the anode and cathode terminals act like a closed switch. The audible or visual alarm 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.
The circuit of Figure can be modified to photograph 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 camera shutter and fire the rifle at the glass bulb, the rifle’s sound will activate the switch.
The strobe does the work of apparently stopping the bullet in midair. If we close the shutter, the position of the bullet in relation to the bulb in the picture will adjusted experimentally by moving the microphone closer to or farther from the rifle.
The strobe does the work of apparently stopping the bullet in midair. If we close the shutter, the position of the bullet in relation to the bulb in the picture will adjusted experimentally by moving the microphone closer to or farther from the rifle.
We use sound activated switch circuit in different ways. For light activated relay switches, machine gun sounds, sound activated FM transmitter, 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.
Smoke Detector
Small change of light the smoke detector 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 voltage-level detector. Smoke Detector is working with the change of voltage. This circuit can be used in 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 sensitivity control is adjusted until the alarm turns off.
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 Ei increases above Vref, Vo switches from –Vsat to +Vsat, causing the alarm to sound.
In initial condition photoconductor 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.
Output voltages not more then supply voltage. The resistive network at the input of the op-amp forms a Wheatstone bridge. This circuit can be used to monitor the level of dust particles in a clean room.
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 summation of input voltages, the result of integrator circuit will be right. Such that, if we give square wave at the input, then we will get triangular wave at the output.
A circuit in which the output voltage waveform of Op amp 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 configuration if the feedback resistor RF is replaced by a capacitor CF.
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 circuits.
When Vin = 0, the integrator of Fig 1(a) works as an open-loop amplifier. This is because the capacitor CF acts as an open circuit (XCF = ∞) to the input offset voltage Vio. In other words, the input offset voltage Vio and the part of the input current charging capacitor CF 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 RF is connected across the feedback capacitor CF. Thus, RF limits the low-frequency gain and hence minimizes the variations in the output voltage.
Both the stability and the low-frequency roll-off problems can be created in ideal integrator. Those problems can be corrected by the addition of a resistor RF. From the simulation 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.
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 differential amplifier is drawn below.
This is a linear bilateral network. So, applying super position theorem, we can find the output voltage equation.
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 feedback loop and control both input and load current from this circuit.
This circuit shown in figure voltage to current converter 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 zener diode tester.
This circuit diagram Figure shows a voltage to current converter in which load resistor RL is floating (not connected to ground). The input voltage is applied to the no inverting input terminal and the feedback voltage cross R1 drives the inverting input terminal. This circuit is also called a current series negative feedback amplifier because the feedback voltage across R1 (applied to the inverting terminal) depends on the output current i0 and is in series with the input difference voltage vid.
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 frequency response of designed active filter by using filter gain equation & plotting the frequency vs. gain curve.
An electric filter is frequency-selective 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. RC filters 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,
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 butter-worth 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,
The above figure shows the frequency response of a 1st order low pass butter-worth filter. 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 fH to pass through it & the signal appears at the output with predefined gain.
Ideally it attenuates the signal appearing at the input which has frequencies greater than fH & gives zero output. Ideally at fH, the frequency response curve changes sharply from AF (closed loop gain) to zero. Hence the frequencies from f to fH are called pass-band frequencies & frequencies greater than fH are called stop-band frequencies.
fH is called high cutoff frequency. Unfortunately the change is not so sharp at fH in practical low pass filters. In practical 1st order low pass butter-worth filter gain changes with 20dB/decade with frequencies greater than fH.
Subscribe to:
Posts (Atom)