Light Controlled Oscillator Circuit

This is a circuit for a light-controlled oscillator, i.e., an oscillator whose output frequency increases with the amount of light shining on it. The main components of this circuit are the 741, a general purpose operational amplifier IC, and the light-dependent resistor or photocell, which serves as the circuit's light collector. This is the figure of the circuit;

The 741 in this circuit is configured as an oscillator driving a piezoelectric buzzer.  The output voltage of the 741 is used as input voltage to the inverting input, which forces the output of the 741 to go back to the opposite level every time it changes state, causing it to toggle between 'low' and 'high' continuously. When the output of the 741 becomes low, this is fed back to the inverting input, causing the 'high' voltage at the non-inverting input to 'dominate' and force the 741 output to go back to 'high'.  When the output of the 741 goes 'high',  this is again fed back to the non-inverting input, which drives the output to go low, and the cycle starts over again.
   
The rate at which the output oscillates depends on how fast capacitor C1 charges and discharges, which in turn depends on the resistance across the light-dependent resistor or photocell. The more light shining on the photocell, the lower is its resistance.  The lower the resistance, the faster capacitor C1 charges or discharges, and the higher is the frequency at which the 741's output oscillates.  This is why this circuit is a light-controlled oscillator - its frequency of oscillation increases as the light shining on it increases.

Digital Voltmeter Circuit

This is a design circuit for digital voltmeter circuit. The integrated circuit ICL7107 is a 3-1/2 digit LED A/D convertor. It contains an internal voltage reference, high isolation analog switches, sequential control logic, and the display drivers. The auto-zero adjustment mechanism ensures zero reading for 0 volts input. The circuit is classic design and you can be sure that it will work fine. However, for better result, it is recommended to design a proper PCB for minimum voltage drift and noise. This is the figure of the circuit;

Connect the positive and negative probes PLG1 and PLG2 to two points of the electric circuit you would like to know their electric potential difference or simply voltage. You have to set the selector switch S2 to proper voltage range you expect those two points would have. To calibrate the volt-meter, use the potentiometer P1. Adjust it to read correct voltage on the display by connecting probes to a known voltage source. You may need to use another calibrated volt-meter in this case.

Beat Frequency Oscillator Simple Metal Detector Circuit

This is a design of metal detector requires alone a scattering of apparatus and an evening’s work. Congenital about a cmos4011 IC, is actual able-bodied and versatile. The 250 kHz advertence oscillator is congenital with two gates (U1/1 and U1/2), C1, R1 and P1. The chase oscillator uses alone one aboideau (U1/3), two capacitors and the chase coil. The outputs of the two oscillators are fed to the fourth aboideau acting as a mixer and filtered with C4. This is the figure of the circuit;

After assembly, affix the headphones and boring about-face P1. The angle will get lower until it disappears. Continuing to circle P1 in the aforementioned administration will account the angle to acceleration again. The point at witch the angle is the everyman and disappears is alleged “zero beat”. If you can not get this aught exhausted abundance for the absolute about-face of P1 you may accept to worst altered ethics for C1.

Turn P1 abutting to the aught exhausted position, again move the chase braid abreast a brownish object. The accent should change, depending on the measurement and ambit of the metal. Note that this simple detector’s achievement is not commensurable to added avant-garde bartering products. It will alone ascertain about ample brownish altar at a abbreviate distance. Coins and added baby altar will be abundant harder to find!

Part List :
· U1: CD4011 (Quad 2-input NAND Gate)
· U2: LM78L05 (5V Regulator IC)
· R1: 2.2k 5% resistor
· R3: 330k 5% resistor
· R4: 270k 5% resistor
· R5: 1k 5% resistor
· C1: 390pF NPO capacitor
· C2, C3: 10nF
· C4: 100nF
· C5: 100uF/16V electrolytic
· C6: 220uF/16V electrolytic
· C7: 100nF ceramic
· P1: 4.7k lin. potentiometer
· L1: 22cm diameter, 14 turns, AWG 26
· K1: SPDT toggle switch
· J1: Headphone jack 1/4 or 1/8 inch

Miniature Audio Oscillator Circuit

This is the circuit for oscillator that is used for the audio. This circuit is based on op amp TL064 for control the circuit. There are only two control pots (RV1 and RV2) and two DPDT switches. The output level pot includes an on-off switch and is of logarithmic taper to allow easier setting at low (i.e. milli volt) levels. This pot is directly coupled to A4's output to minimize response errors, provided that the load impedance is constant or quite high compared to the output impedance provided by Mini oscillator. This is the figure of the circuit.


The frequency sweep control (RV1A/B) has a range of about 24:1 and in combination with the High-Low range switch having a 18:1 ratio, the audio band is covered (with the exception of the lowest octave) in two overlapping ranges. The possibility of a single sweep of the audio band without the range switch was tried out and later dropped in preference to the present design. The square/sine wave switch works by disconnecting the negative feedback around A4 allowing the op-amp to run "open loop". In this condition it is overdriven by the oscillator stage causing its output to saturate at the positive and negative supply voltages producing a squared waveform. The additional four diode network which is switched across the output of A4 and voltage limits the output level in square wave mode to match the sine wave level and at the same time regulates against variations in the battery voltage.

The actual operating level of Miniosc is limited by the use of a single nine volt battery. The discharge curves for various types show a voltage variation of from 9.5 volts down to 6.3 volts is to be expected from "fresh" to "flat". The miniosc operates as specified over this range with a maximum output level of 1.27 volts RMS sine and 1.45 volts square. The battery drain in sine wave mode is a miniscule 1.7mA increasing to about 4.7mA in square wave mode. This very low drain is mainly the result of using the Texas Instruments TL064 low power quad FET op-amp which is ideally suited to the design.

Lamp Stabilized Wien Bridge Oscillator

This circuit is design for the oscillator with the lamp stabilizer. The frequency range switching is done with a 4 position, 2 pole rotary switch, and the capacitors should be wired directly to the switch to minimize stray capacitance. This is the figure of the circuit.


The circuit is a low power version of a simple power amplifier, and will provide the necessary 3.16V RMS easily using a +/-12V supply. Peak amplitude is about +/- 4.5V, and a simple emitter follower buffer is used to drive the output voltage divider (see below for level control, buffer and output attenuator). Current in the output stage and buffer is quite high at 8mA, and a small heat sink is a good idea for the output devices (those with the 33 Ohm emitter resistors). They will be dissipating about 100mW each under normal operating conditions with a +/- 12V supply. Likewise, heat sinks should be used on the power supply regulators (these are normally not needed when powering a few conventional op amps). The diodes shown are 1N4001 or similar. Resistors are all 1/4 Watt 1% tolerance metal film, and a cermet multi-turn pot is recommended for the 500 Ohm variable resistor.

Precision Relaxation Oscillator Circuit

This is a circuit for precision oscillator that is the basic design using a voltage to frequency converter and based on op amp LM131. Basically, this IC, like any V/F converter, is a precision relaxation oscillator that generates a frequency linearly proportional to the input voltage. As might be expected, the circuit has a capacitor, CL, with a saw tooth voltage on it. This is the figure of the circuit.


The general description about this circuit is the circuit is a feedback loop that keeps this capacitor charged to a voltage very slightly higher than the input voltage, VIN. If VIN is high, CL discharges relatively quickly through RL, and the circuit generates a high frequency. If Vin is low, CL discharge slowly, and the converter puts out a low frequency. When CL discharges to a voltage equal to the input, the comparator triggers the one-shot. The one-shot closes the current switch and also turns on the output transistor. With the switch closed, current from the current source recharges CL to a voltage somewhat higher than the input. Charging continues for a period determined by RT and CT. At the end of this period, the one-shot returns to its quiescent state and CL resumes discharging. [Circuit’s source: National Semiconductor, Inc].

Oscillator Circuit with 50% Duty Cycle

This is a circuit f oscillator that can be configured to give symmetric oscillation (50% duty cycle). This circuit is using 555 timer IC for produces the 50% duty cycle. Other circuit uses diodes to split the charging and the discharging paths through different resistors, but here we need no such diodes. This is the figure of the circuit.


The time period for the output high is the same as regular configuration;
t1 = 0.693 RA C,
But for the output low, the period is;
t2 = [(RA.RB/(RA+RB)] x C x Ln[(RB-2RA)/(2RB-RA)]
Thus the oscillator frequency is equal to 1/(t1+t2).

Please remember this oscillator circuit will not oscillate if RB is greater than 1/2 RA because the junction of RA and RB cannot bring pin 2 down to 1/3 VCC and trigger the lower comparator.

Wien Bridge Oscillator Circuit

This is a circuit that is known as wien bridge oscillator circuit. The circuit has positive and negative feedback loop. This circuit is work with control by op amp. This is the figure of the circuit.


The circuit oscillates at a frequency determined by the RC time constant at frequency and produces a sinusoidal waveform at the output voltage Vout. In many cases this circuit is used as sine wave generator which is using rail to rail op amp. [Schematic’s diagram source: Advanced Linear Devices, Inc]

Tuned Sine Wave Oscillator Circuit

This is a design circuit for sine wave oscillators that will provide both a sine and square wave output for frequencies from below 20 Hz to above 20 KHz. The frequency of oscillation is easily tuned by varying a single resistor. This circuit is controlled by two op amp, LM111 and LM101A. This is the figure of the circuit.


In this circuit, an operational amplifier has function as a tuned circuit, driven by square wave from a voltage comparator. The frequency is controlled by R1, R2, C1, C2, and R3, with R3 used for tuning. Tuning the filter does not affect its gain or bandwidth so the output amplitude does not change with frequency. A comparator is fed with the sine wave output to obtain a square wave. The square wave is then fed back to the input of the tuned circuit to cause oscillation. Zener diode, D1, stabilizes the amplitude of the square wave fed back to the filter input. Starting is insured by R6 and C5 which provide dc negative feedback around the comparator. This keeps the comparator in the active region. [Schematic diagram source: National Semiconductor. Inc]

Phase Shift Oscillator Circuit

This is a design circuit of a simple inexpensive amplitude stabilized phase shift sine wave oscillator which requires one IC package, three transistors and runs off a single supply. This circuit is combination with the RC network comprises a phase shift configuration and oscillates at about 12 kHz. The remaining circuitry provides amplitude stability. Here’s the schematic figure of the circuit.


The high impedance output at Q2's collector is fed to the input of the LM386 via the 10 μF-1M series network. This circuit is using op amp LM386 causes it has fixed gain of 20. The 1M resistor in combination with the internal 50 kΩ unit in the LM386 divides Q2's output by 20. The positive peaks at the amplifier output are rectified and stored in the 5 μF capacitor. This potential is fed to the base of Q3. Q3's collector current will vary with the difference between its base and emitter voltages. Since the emitter voltage is fixed by the LM313 1.2V reference, Q3 performs a comparison function and its collector current modulates Q1's base voltage. Q1, an emitter follower, provides servo controlled drive to the Q2 oscillator.

Low Distortion Sine Wave Oscillator Circuit

One approach to generating sine waves is to filter a square wave. This leaves only the sine wave fundamental as the output. Since a square wave is easily amplitude stabilized by clipping, the sine wave output is also amplitude stabilized. For the solution of the problem, you can look at the figure below.


A lower distortion oscillator is needed. It can be used. Instead of driving the tuned circuit with a square wave, a symmetrically clipped sine wave is used. The clipped sine wave, of course, has less distortion than a square wave and yields a low distortion output when filtered. This circuit is not as tolerant of component values as tune sine wave oscillator. To insure oscillation, it is necessary that sufficient signal is applied to the zener for clipping to occur. Clipping about 20% of the sine wave is usually a good value. The level of clipping must be high enough to insure oscillation over the entire tuning range. If the clipping is too small, it is possible for the circuit to cease oscillation due to tuning, component aging, or temperature changes. Higher clipping levels increase distortion. [Schematic’s diagram source: National Semiconductor. Inc]

Free Running Oscillator Circuit

This is a circuit for oscillator using astable mode operation. The basic oscillatior is using 555 timer IC. This circuit is also give mode free running oscillator. This is the figure of the circuit.


Operation of the circuit is begin, when initialy by capacitor C charged towards 2/3 V+ with Ra and Rb. When voltage on C reaches that threshold level, the discharge output in pin 7 is turning on to discharging C. Using CMOS 555 timer IC is a very wide frequency at very low of voltage spikes and dissipation can be achieved. Selections of values the Ra and Rb is limited by input leakage specification at time in pin 7, 2, and 6. [Schematic’s diagram source: Advanced Linear Devices, Inc].

Wien Bridge Oscillator Using CA3140

This is a bridge oscillator circuit. This circuit is excellent use of its high input impedance, high slew rate, and high voltage qualities and it is called the Wien Bridge sine wave oscillator. This is the figure of the circuit.


Oscillator stabilization takes on many forms. It must be precisely set, otherwise the amplitude will either diminish or reach some form of limiting with high levels of distortion. The element, RS, is commonly replaced with some variable resistance element. Thus, through some control means, the value of RS is adjusted to maintain constant oscillator output. A FET channel resistance, a thermistor, a lamp bulb, or other device whose resistance increases as the output amplitude is increased are a few of the elements often utilized. As the output signal amplitude increases, the zener diode impedance decreases resulting in more feedback with consequent reduction in gain; thus stabilizing the amplitude of the output signal. [Project Schematic source: Intersil Corporation].