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This is the Simple Universal Laboratory Power Supply Circuit Diagram. The value of the design lies in the use of IC1, an LM317HVK adjustable s.eries-pass voltage regulator, for broad-range performance remainder supplies voltage-setting and current-limiting functions.
The input to ICI-comes from the output of BR1, which is filtered by CI and C2 to about +60 Vdc, and the input for current-sense comparator IC2 comes from BR2, which also acts as a negative bias supply for regulation down to ground.
Universal Laboratory Power Supply Circuit Diagram
Simple Universal Laboratory Power Supply Circuit Diagram
This Audio Amplifier circuit is useful in classrooms to reduce the strain of lecturing ,if the surrounding environment is noisy. It uses the power amplifier IC LM 380 that gives 2 watts output which is sufficient in a confined area. The Amplifier is portable and the whole circuit and the battery can be enclosed in the Speaker box itself.
The circuit uses a preamplifier stage around NPN transistor BC 548 and a power amplifier around LM380.An external Collar MIC can be given to the input using an audio jack .The voice signals are amplified by T1 and fed to IC1 input through the volume control VR. Capacitor C3 reduce the undesirable howling from the speaker.
LM380 is the general purpose audio amplifier and its gain is internally fixed at 34 dB. Its output is short circuit proof with internal thermal limiting. The IC works between 5 to 22 volts DC and is dual in line version.
Classroom Microphone Circuit diagram
Assemble the circuit on a common PCB. A 9 volt PP3 battery can be used to make the unit compact. If the amplifier is used for many hours, a 6 Volt 4.5 Ah rechargeable battery is a nice choice. If it is used, a charger input facility should be provided .Use a small good quality 8 Ohms speaker. If the output is not sufficient, use a high power amplifier IC circuit in the place of LM 380.
LM 380 Pin connection
This circuit produces a ringing sound similar to that made by more recent telephones. It consists of three almost identical oscillators connected in a chain, each generating a squarewave signal. The frequency of each oscillator depends on the RC combination: R4 and C1 around IC1.A, R8 and C2 around IC1.B and R12 and C3 around IC3.C. The pairs of 100 kΩ resistors divide the asymmetric power supply voltage (between 5 V and 30 V) so that, in conjunction with the 100 kΩ feedback resistors (R3, R7 and R11) either one third or two thirds of the supply voltage will be present at the non-inverting inputs to the opamps. The voltage across the capacitor therefore oscillates in a triangle wave between these two values.
Electronic Telephone Ringer Circuit diagram
The first oscillator is free-running at a frequency of approximately 1/3 Hz. Only when its output is high, and D1 stops conducting, can the second oscillator run. The frequency of the second oscillator is about 13 Hz, and optional LED D3 flashes when it is running. When the output of the second oscillator is low, the third is allowed to run. The frequency of the third oscillator is around 1 kHz, and this is the tone that is produced. The second oscillator is not absolutely necessary: its function is just to add a little modulation to the 1 kHz tone. A piezo sounder is connected to the output of the third oscillator to convert the electrical signal into an acoustic one. The current consumption of the circuit is just under 1mA with a 5V power supply, rising to about 1.65mA with a supply voltage of 15 V.
Source: http://www.ecircuitslab.com/2012/07/electronic-telephone-ringer.html
Voltage to frequency converter circuit diagram has a 1 Hz-to-30 MHz output, 150-dB dynamic range, for a 0 to 5 V input. It maintains 0.08% linearity over its entire 71/3 decade range with a full-scale drift of about 20 ppm/°C.
To get the additional bandwidth, the fast )FET buffer drives the Schottky TTL Schmitt trigger. The Schottky diode prevents the Schmitt trigger from ever seeing negative voltage at its input. The Schmitt`s input voltage hysteresis provides the limits which the oscillator runs between.
Voltage to Frequency Converter Circuit Diagram
Voltage to Frequency Converter Circuit Diagram
