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A retriggerable monostable multivibrator and a D flip-flop can form a simple, yet reliable frequency comparator that compares an input frequency with a predetermined reference. To determine whether an input frequency (f) falls between two known frequencies, f1 and f2, two one-shot/flip-flip combinations are used, as shown. Here both the one-shot and the flip-flop ICs are wired for positive-edge triggering. Each input pulse causes the monostable output to go high for the period of its preset timing interval. The flip-flop is triggered simultaneously, but its output is determined by the state of its D input at the time of trigger threshold. If the period of the input frequency is shorter than the preset timing of the monostable, a constant high level will be present at the D input, forcing the flip-flop’s Q output to remain high. If the input frequency period becomes greater than that of the monostable, the flip-flop’s Q output will go low. VR1, VR2, and C1, C2 determine the value of...

Single Phase Induction Type Energy Meter Single phase induction type energy meters are extensively used for the measurement of electrical energy in single phase A.C circuits. One can find such meters installed in homes. It is also called as single phase watt-hour meter. Single Phase Induction Type Energy Meter Principle: torque is produced to rotate the disc is due to interaction of two fluxes. Since the e.m.f induced in the disc by induction, this instrument operates on A.C only. Construction: The below fig shows the various parts of a single phase induction type energy meter. It consists of a shunt magnet, a series magnet, a rotating disc, a brake magnet and a counting mechanism. The shunt magnet consist of a number of M shaped iron laminated core wound with a fine wire of many turns i.e. coils and is connected across the supply. The shunt coil carries a current proportional to supply voltage and is known as Pressure coil . The flux produced by shunt magnet lags behind the supply v...

Volt meters & ampere meter with PIC can be used to measure voltage and current simultaneously. The series of volt meters & ampere meter with PIC16F876A PIC is used as a data processor voltage and current are measured.  This circuit uses the viewer in the form of 16 × 2 LCD used for the data display voltage and current measurements. In the article volt meter and ampere meter with PIC are discussed kerannya limited to devices only. More detail can be seen from the image sequence volt meter and ampere meter with PIC below.  The images of Volt Meter & Ampere Meter With PIC Circuit Volt meters & ampere meter with PIC  

Also suitable for Headphones Operates in conjunction with a DVM A simple Impedance Meter can be useful to measure the actual impedance a loudspeaker or headphone is presenting @ 1kHz standard frequency. The circuit, designed on request, relies on an earlier design (Spot-frequency Sine wave Generator) to obtain a stable, low distortion 1kHz sine wave avoiding the use of thermistors, bulbs or any special amplitude-limiting device. The sine wave output, after some amplitude setting obtained by means of P1, is sent to the device under measurement through a resistor. A regulated supply is necessary to obtain a stable output waveform. D1 and D2 force IC1 to deliver 6.2V output instead of the nominal 5V. The measurement is done in two stages: as a constant current supply of the device under test is necessary, this can be set at first by adjusting P1 and measured across the series resistor (R7 or R8, depending on the impedance value to be measured); then, the meter is switched across the devic...

This project will indicate the volume level of the audio going to your speakers by lighting up LEDS. The LEDS can be any color so mix them up and really make it look good. The input of the circuit is connected to the speaker output of your audio amplifier. You want to build two identical units to indicate both right and left channels. The input signal level is adjusted by the 10k ohm VR. If you wish to make a very large scale model of this unit and hang it on your wall there is an optional output transistor that can drive many LEDS at once. The unit I built drove three LEDS for each output. The sequence of the LEDS lighting are as follows Pin 1, 18, 17, 16, 15, 14, 13, 12, 11, 10. visit page. via next.gr Simple Stereo VU Meter

Here is a Simple LED Volt meter to Monitor the charge level in Lead Acid Battery or Tubular battery. The terminal voltage of the battery is indicated through a four level LED indicators. The nominal terminal voltage of a Lead Acid battery is 13.8 volts and that of a Tubular battery is 14.8 volts when fully charged. The LED voltmeter uses four Zener diodes to light the LEDs at the precise breakdown voltage of the Zener diodes. Usually the Zener diode requires 1.6 volts in excess than its prescribed value to reach the breakdown threshold level. When the battery holds 13.6 volts or more, all the Zener breakdown and all LEDs light up. When the battery is discharged below 10.6 volts, all the LEDs remain dark. So depending on the terminal voltage of the battery, LEDs light up one by one or turns off. LED Volt Meter Circuit Circuit diagram: LED Volt Meter Circuit Diagram Author: D. Mohan Kumar Copyright: electroschematics.com

All technicians must have the same experience that the old models of aircraft generally have several common Elco its dry or down in value, mainly found in many brands of china plane. Eco is dry can cause a variety of disorders that are sometimes difficult to trace or even be able to make certain parts do not work at all, especially if used on a circuit that works at such high frequency SMPS (Switch Mode Power Supply) and the horizontal. Elco dry technicians sometimes make headaches and time consuming when you track the damage. Many technicians get around this problem by directly replacing all existing Elko, the Elko-regardless of whether Elko is corrupt or not. It is generally quite successful. But sometimes the quality is not good substitutes Elko, so the damaged aircraft back after use for some time. Replace all of Elko is also a problem for yourself if the circuit is improved a lot using Elko. The use of ESR-meter proved to be the most appropriate choice to solve the above problems....

Circuit Diagram Description The circuit was designed to create a low cost frequency meter that will cover the range of 1 Hz to 1 MHz with a digital indication using three 7-segment displays. Terminology 7805 – a 3-terminal 1A positive voltage regulator with output transistor safe area compensation, internal short circuit current limiter, output voltage of 5V, 12V, and 15V, internal thermal overload protection, no external components, and current output in excess of 0.5A 4026 – a decade counter where the count advances as the clock input becomes high and has a maximum current of about 1 mA with a 4.5 V supply and 4 mA with a 9 V supply, which can light the appropriate segments of a common cathode 7-segment display 4583 – a 4-bit single-chip microcomputer designed with CMOS technology using a simple, high-speed instruction set, equipped with four 8-bit timers, a 10-bit A/D converter, interrupts, oscillation circuit switch function, and used in application with remote control transmitt...

The Capacitance Meter Circuit, However, when finished, you will have an instrument capable of measuring all but the largest capacitors used in radio circuits. Unlike variable resistors, most variable capacitors are not marked with their values. As well, the markings of capacitors from salvaged equipment often rub off.

I like to see lights move to music. This project will indicate the volume level of the audio going to your speakers by lighting up LEDS. The LEDS can be any color so mix them up and really make it look good. The input of the circuit is connected to the speaker output of your audio amplifier. You want to build two identical units to indicate both right and left channels. The input signal level is adjusted by the 10k ohm VR. If you wish to make a very large scale model of this unit and hang it on your wall there is an optional output transistor that can drive many LEDS at once. The unit I built drove three LEDS for each output. The sequence of the LEDS lighting are as follows Pin 1, 18, 17, 16, 15, 14, 13, 12, 11, 10.

This is a simple 30V volt meter using PIC16F676 micro controller with 10-bit ADC (analog to digital converter) and three 7 segment LED displays. You can use this circuit to measure up to 30V DC. The possible applications are on bench power supply or as a digital panel meter in various systems. PIC16F676 is the heart and brain of this circuit. The internal adc of the mcu with a resistor network voltage divider is used to measure the input voltage. Then 3 digits of comm anode 7 segment display is used to display final converted voltage. As you can see in the schematic the displays are multiplexed with each other. It means we switch on one display and put the corresponding digit on this while other two displays are off this cycle goes for each of the displays.

Power Factor Meter The power factor of an A.C circuit can be calculated from the following relation by measuring the current, voltage and power. I.e. cosΦ = P/VI. This method of determining the power factor of an electrical A.C circuit, is however, of low accuracy has a number of draw backs. Hence, it is desirable to have an instantaneous indication of the power factor of an A.C circuit, especially where it is varying continuously. Therefore, a power factor meter is connected in the A.C circuit to measure power factor which indicate directly by a single reading. There are two types of power factor meters: 1.        Electrodynamometer type of p.f meters                (a)      Single phase                 (b)      Three phase 2.        Moving iron type p.f meters             ...

Also suitable for Headphones Operates in conjunction with a DVM . A simple Impedance Meter can be useful to measure the actual impedance a loudspeaker or headphone is presenting @ 1kHz standard frequency. The circuit, designed on request, relies on an earlier design (Spot-frequency Sine wave Generator) to obtain a stable, low distortion 1kHz sine wave avoiding the use of thermistors, bulbs or any special amplitude-limiting device. The sine wave output, after some amplitude setting obtained by means of P1, is sent to the device under measurement through a resistor. A regulated supply is necessary to obtain a stable output waveform. D1 and D2 force IC1 to deliver 6.2V output instead of the nominal 5V. The measurement is done in two stages: as a constant current supply of the device under test is necessary, this can be set at first by adjusting P1 and measured across the series resistor (R7 or R8, depending on the impedance value to be measured); then, the meter is switched across the dev...

This is the simple Stereo VU Meter Circuit Diagram. This project will indicate the volume level of the audio going to your speakers by lighting up LEDS. The LEDS can be any color so mix them up and really make it look good. The input of the circuit is connected to the speaker output of your audio amplifier. You want to build two identical units to indicate both right and left channels. The input signal level is adjusted by the 10k ohm VR. If you wish to make a very large scale model of this unit and hang it on your wall there is an optional output transistor that can drive many LEDS at once. The unit I built drove three LEDS for each output. The sequence of the LEDS lighting are as follows Pin 1, 18, 17, 16, 15, 14, 13, 12, 11, 10. Stereo VU Meter Circuit Diagram  

This is a simple audio Milli volt meter circuit diagram . This Audio Milli Volt Meter Circuit has a flat response from 8Hz to 50 kHz at -3 db on tbe 10-mV range. The upper limit remains the same on tbe less sensitive ranges, but the lower frequency limit covers under 1 Hz. Simple Audio Milli Volt Meter Circuit Diagram

This is an audio power meter simple with this circuit , dual LED starts to light green around 0.1 watts into 8 ohms ( 0.2 watt into 4 ohms ) . Naturally, this depends on the specific type of LED is used. Despite being a simple equipment he is impressively bench since with a load resistor connected to output of speakers is possible to measure the sound level up , or just check its output . Audio Power Meter Circuit Diagram  

The water-tank level meter de-scribed here is very simple and useful for monitoring the water level in an overhead tank (OHT). The water level at 30cm intervals is monitored and continuously indicated by LEDs ar-ranged in a meter-format. When all the LEDs are ‘off’, it indicates that the OHT is empty. When the water level reaches the top limit, the whole LED-meter begins to flash. The height at which the level-sensing electrodes are fitted is adjustable. Thus, the minimum and maximum level settings may be varied as desired. The range of the meter can also be enlarged to cater to any level. No special or critical components are used. CMOS ICs are used to limit the idle current to a minimum level.   Even when all the LEDs are ‘on’, i.e. water reaches the top level, the demand on the power supply is reasonably low. Further, the extremely high input resistance of the Schmitt inverter gates reduces the input current and thus minimises the erosion of electrodes. The princi-pal part of...