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8051 / 8052
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4 Band Resistor
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Meter Counter Circuits
Digital weight scale
This circuit employs a potentiometer as the weight sensing element. An object placed upon the scale displaces the potentiometer wiper, an amount proportional to its weight
This circuit provides a low cost and reliable method of testing zener diodes. RVl can be calibrated in volts, so that when LED 1 just lights, the voltage on pins 2 and 3 are nearly equal. Hence, the zener voltage can be read directly from the setting of RVl. The supply need only be as high a value as the zener itself
The circuit tests whether or not a diode is open, shorted, or functioning correctly. If lamp A lights, the diode under test is functional. When lamp B is lit, the diode is good but connected backwards
Sensitive rf voltmeter
This circuit measures RF voltages beyond 200 MHz and up to about 5 V. The diode should be mounted in a remote probe, close to the probe tip. Sensitivity is excellent and voltages less than 1 V peak can be easily measured
Precision calibration standard
An external power supply that gives a voltage higher than the highest expected rating of the zener diodes to be tested is required. Potentiometer RVl is adjusted until the meter reading stabilizes
Visual modulation indicator
Indicator lamp brightness varies in step with modulated RF signal. Adjust R2 with transmitter on (modulated) until the lamp flashes in step with modulation
Power meter 1KW
The circuit is intended for 117 Vac Â± 50 Vac operation, but can be easily modified for higher or lower voltages. It measures true (nonreactive) power beingdeliveredto the load and requires no external power supply. Idling power drain is only 0 W. Load current sensing voltage is only 10 mV, keeping load voltage loss to 01%, Rejection of reactive...
Low resistance continuity tester
This tester can be used to check IC printed circuit boards. Two 4 K resistors and the transistors connected to them prevent current flow through the operational amplifier until the probe circuit is completed
Linear scale ohmmeter
One preset resistor is used for all the ranges, simplifying the setting up. Diode clamping is included to prevent damage to the meter if the unknown resistor is higher than the range selected
Peak detect and hold
If the voltage at the input exceeds the voltage on the capacitor, then the output of the 741 goes positive, the diode conducts, and the capacitor is charged up to the input voltage-forward voltage drop of diode. When the voltage at the input is less than that on the capacitor, the output of the 741 goes negative, and the diode cuts off
Sample and hold
The JFETs, Ql and Q2, provide complete buffering to Cl, the sample and hold capacitor. During sample, Ql is turned on and provides a path, rds(on), for charging Cl. During hold, Ql is turned off, thus leaving Ql Id (< 100 pA) and Q2 Igss (< 100 pA) as the only discharge paths
High speed sample and hold
This circuit exhibits a 10 V acquisition time of 900 ns to 0% accuracy and a droop rate of only 100 Âµ-V/ms at 25Â° C ambient condition. An even faster acquisition time can be obtained using a smaller value hold-capacitor. By decreasing the value from 1000 pF to 220 pF, the acquisition time improves to 500 ns for a 10 V step
The circuit charges and discharges a capacitor at a crystal-controlled rate, and stores on a sample-anddifference amplifier the change in voltage achieved. The current that flows during the discharge cycle is averaged, and ratiometrically measured in the a/d using the voltage change as a reference. Range switching is done by changing the...
U1a is an oscillator and U1b tbe measurement part of tbe circuit. It converts unknown capacity into a pulse-width modulated signal the same way anÂ·automotive dwell meter works. The meteris linear so tbe fraction or percentage of time that tbe output is high is directly proportional to the unknown capacitance (CXin the schematic).
The two-pole, five-position switch, coils and 365-pF variable capacitor cover a range from 1.5 to 30 MHz. The amplifier uses Darlington npn transistors whose high beta, 5000, provides high sensitivity with Sl used as the amplifier on/off switch. Switch S2 in the left position allows the output of the 1N34 diode to be fed directly into the...
The untuned, but amplified FSM can almost sense that mythical flea"s whisper-from 3 through 148 MHz no less-and yet, is so immune to overload that the meter pointer won"t pin. The key to the circuit is the amplifier, a 324 quad op amp, of which only one section is used.
The circuit monitors and displays a digital signal"s duty cycle and provides accuracy as high as Â±1%. Using switch S2, you can choose a frequency range of either 250 Hz to 2. 5 kHz at Â±1% accuracy or 2 kHz to 50 kHz at Â±10% accuracy. The common-cathode display gives the signal"s duty-cycle percentage. Phase-locked loop re4 and counters...
This circuit is designed around a 4049 hex inverter/buffer. Two inverters are used ina dual-frequency signal-injector circuit, another inverter is used as a logic probe, and the remaining three inverters are used as a sensitive dual-input, audio-signal tracer. The signal-injector portion gates are configured as a two-frequency,...
The Hewlett-Packard HSCH-3486 zero-bias Schottky diode is used as the detector. To avoid using a modulation method of detection, a chopperstabilized op amp is used. The chopper op amp basically converts the input de voltage to ac, amplifies it, and converts it back to de. Amplifying the de output from the detector 150 times with a chopper...
The circuit is based on the grid-dip or absorption effect, which occurs when a parallel resonant circuit is coupled to an oscillator of tbe same frequency. Ql operates in a conventional Colpitts oscillator circuit at a fixed frequency of approximately 4 MHz. A meter connected in series with tbe transistor"s base-bias resistor serves as the...
In machine and equipment design. some applications require measurement of both the shaft speed and the direction of rotation. Fig. 56-4 shows the circuit of a tachometer, which also indicates the direction of rotation. The flywheel has two magnets embedded in the outer rim about 45Â° apart. One magnet has the north pole toward the outside and...
This circuit operates by charging a small capacitor from a constant-current source when the pulse to be measured is present. Dual pnp transistor Q3 is the current source; its output current equals the LM329 reference voltage divided by the resistance of potentiometer Rl. When the input is high with no pulse present, Ql keeps the current...
The design shown is a simple unit for QRP operation on all authorized frequencies up to 30 MHz. based on a toroidal transformer Tl. The secondary winding of Tl samples a small amount o1 rf power. both forward and reflected, which is divided by the bridge circuit and rectified by diodes Dl and D2. Forward and reflected readings are obtained...
The circuit in Fig. 56-lla lights the signal lamp upon detecting a line current consumption of more than 5 mA, and handles currents of several amperes with appropriate diodes fitted in the D1 and D2 positions. Transistor T1 is switched on when the drop across Dl/D2 exceeds a certain level. Diodes from the well-known 1N400x series can be used...
The circuit outputs power to the drive motor when one or no sheets are being fed, but interrupts motor power when two or more superimposed sheets pass through the optodetector slot. The optodetector can be either an H2aB darlington interruptor module or an H23B matched emitter -detector pair. The output from the optodarlington is coupled to a...
The CS209 is designed to detect the presence or proximity ofmagnetic metals. It has an internal oscillator that, along with its external lc resonant circuit, provides oscillations whose amplitude is dependent upon the Q of the lc network. Close proximity to magnetic material reduces the Q of the tuned circuit, thus the oscillations tend to...
In this application, the ICM7249 is configured as an hours-in-use meter and shows how many whole hours of line voltage have been applied. The 20-MD resistor and high-pass filtering allow ac line activation of the SIS input. This configuration, which is powered by a 3-V lithium cell, will operate continuously for 21/z years.
A transducer senses a direct current magnetically, providing isolation between the input and the output. The detecting-and-isolating element is a saturable reactor, in which the input current, to be measured, passes through a one-tum control coil. The transducer provides an output of 0 to 3 Vdc, an input current of 0 to 15 Adc, and consumes...
This design is for an external signal strength meter that is analog, digital, and audible for mobile transmitter hunters. The S meter also incorporates a gain circuit. The digital LED bar graph display has a very fast response time. The 3.3-KO resistor near LM3914 can be replaced with a 5-K pot to control LED brightness. The S2A position...
Remote, noncontact, measurement of the speed of rotating objects is the purpose of this simple circuit. Linearity and accuracy are extremely high and normally limited by the milliammeter used and the initial calibration. This circuit is configured to count the leading edge of light pulses and to ignore normal ambient light levels. It is designed...
The adapter allows four inputs to be displayed simultaoeously on a single trace scope. For low-frequency signals, less than 500Hz, the adapter is used in the chop mode at a frequency of 50 kHz. The clock can be run faster, but switching glitches and the actual switching time of the DG201A limit the maximum frequency to 200 kHz. High...
This circuit turns a common oscilloscope into a versatile eight-channel display for direct voltages. The trend of each of the eight input levels is readily observed, albeit that the attainable resolution is not very high. The circuit diagram shows the use of an eight-channel analog multiplexer IC1, which is the electronic version of an...
Frequency Meter Circuits
VU Meter Circuits
Ultrasonic distance finder circuit
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is measured. There are three main categories of distance measurement methods in use: a) By...
Simple Metal detector circuit with CD4030
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to find something potentially valuable, hidden a few centimeters below the soil. So many...
Fully automatic watering circuit for flower pots
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This circuit comes as a solution to this problem. Depending on humidity of the pot at...
Simple deep searching metal detector circuit
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the circuit of this metal detector, it is possible to detect a metal coin in depth of 90 to...
Sub-Harmonic Bass Converter for Electric Guitars
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound, such as filtering or distortion. Instead, a frequency division system produces outputs...
Echo Depth Sounding Sonar for Boats
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the calibration of the rope. This arrangement still exists in some yachts. The big...
100W HiFi Audio Amplifier Circuit
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power supply must be symmetrical so that no electrolytic capacitors are needed at the outlet....
Plant-Pot Water Level Indicator Circuit
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower. The circuit of the device is shown in Figure 2. The water detection is made from the bottom...
Analogue Sound Preasure dB-Meter Circuit
The best human ear can capture sounds from 20Hz to 20KHz. These limits are known to be the broadest that can exist. Normally the normal limits range from 100Hz to about 13KHz and depend on the age and health of the individual. We for our measurements and to have a good accuracy we will get the limits of 20Hz to 20KHz. A sound to be heard does...
Digital Signal Integrity
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