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Video Switch Circuit Schematic Diagram
Video switcher circuit is needed to display more than one display in one monitor. Take a look at below circuit schematic : MAX454 is the core of this video. It is a video multiplexer-amplifier assembled by MAXIM Semiconductor. Pay attention when designing the video signal path around this chip. Track of ground plane can be inserted between video...
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2G—10 Band Stereo Graphic Equaliser circuit diagram
This circuit must be connected before the amplifier circuit. For maximum performance, you may use high quality electronic component such as metalfilm resistor, MKM capacitor (nonpolar), tantalum capacitor (bipolar). You may replace the power supply module with regulated and stabilized power supply or just add IC LM7815 after R35 and IC LM7915 afte
Radio and communication circuits
A regenerative SW receiver with automatic regeneration control
This is the tuned radio frequency receiver for shortwave (25 meter band, 11. 7. 12. 1 MHz). It was created as experimental design for further experiments with the autodyne synchronous receiver (see Polyakov V. T. Autodyne synchronous regenerative receiver. - Radio, 1994, N 3, page. 10. ). The circuit diagram is shown in Figure 1. The input...
AM Synchronous Demodulator
The advantage of synchronous reception of AM signals is widely known. It includes high selectivity, linearity of detection and a low noise level at the output compared to other ways of reception. The circuit diagram is shown in figure 1. The operation of the circuit is based on method of direct locking of the local oscillator frequency by the inpu
Bipolar stepper motor driver circuit diagram
This circuit produces the power to drive a bipolar stepper motor. The rotation speed and the rotation direction of the stepper motor can be changed. This circuit consists of two integrator circuits (A1, A3) and the amplifier (A2) connected in series. This connection provides necessary feedback to get the oscillation. The circuit is u
Digital sine wave generator
By using the reverse binary counter and the binary-coded decimal decoder can obtained the step voltage, and by approximating this voltage can be produced the sine wave signal with sufficient accuracy, suitable for many purposes. In the circuit diagram of the digital generator (see figure 1) the resistors R1. R9 is used to produce the first quarter
Digital Sine Wave Oscillator
The schematic diagram shown in Figure 1 have the ability to synthesize a sinusoidal waveform with a frequency of 0. 01 Hz to 1 MHz. The clock signal feeds to the input of the binary counter IC1, this clock frequency is 32 times more than the output sinusoidal signal. The outputs Q0. Q3 of the counter IC1 are connected through the logic gates XOR...
FM Crystal Radio Receivers
The notion of "crystal radio" is strongly associated with huge antennas and radio broadcasting on long and medium bands, in this article, the author describes the experimentally tested detector circuits of VHF receivers designed to listening to a FM stations. The very possibility of receiving VHF FM detector was discovered accidentally. One day I
FM receivers with PLL
This article describes some simple FM direct conversion radio receivers with phase-locked loop (PLL). This receivers uses the method of locking the local oscillator frequency with the input signal . All this FM receivers are based on the circuit shown in fig. 1. This is a combined oscillator and mixer, and it works as a synchronous detector. Th
Measuring the radiation can be made not only with expensive factory-made instrument. The simplest device (see Figure 1), can be build if you have a counter (radiation detector) type SBM-20 or similar. The circuit is powered by a 220 volts AC 50/60Hz. The double-voltage rectifier circuit is made of diodes VD1, VD2, and capacitors C1, C2. The DC vol
HAM RADIO SW RECEIVER
A simple radio receiver circuit is shown in Fig. 1. This receiver is designed for reception of signals of amateur radio stations operating in the SW band of 10, 15, 20, 40 and 80 meters. This direct-conversion receiver consists of a set of an input bandpass filters tuned to the middle frequency of the amateur bands, a broadband RF amplifier based
Hidden wire detector
If you want to drill a hole in the wall then you must be sure that there`s no electrical wiring. This simple device. shown on the figure 1, can detect electrical wiring in the walls or ceiling. Resistor R1 protects IC CD4011 against electrostatic. A rigid copper piece of wire (~ 18 AWG, with length of 5. 15 cm) works as antenna. Sensitivity of the
How to improve the selectivity of the FM radio receiver
The FM radio receiver with PLL designed by A. Zaharov  still attracts the attention of radio amateurs. As noted in a publication of the magazine "Radio" [2, 3], one of the major drawbacks of this type of detectors is the low adjacent channel selectivity. The reason for this is the direct detection of strong signals by base-emitter junction of t
Linear AC voltmeter circuit diagram
The use of diode rectifiers in AC voltmeters with a low lower limit of measurement range (0. 5. 1 V) leads to significant nonlinearity of the scale because of the nonlinearity of current-voltage characteristics of diodes. The use of electronic amplifiers in rectifier circuits allowing to linearize the scale but requires a power supply. At the...
Loudspeaking crystal radio receivers
A lots of radio amateurs have an interest to power a simplest radio receivers with the "free energy", i. e. the energy, taken by the receiver antenna directly from the air. The circuits described here can provide a radio reception using a loudspeaker. The question of how much power can get out of a signal from an antenna, and how to build a loudspe
Loudspeaking radio receiver with a bridge amplifier powered by free energy
While experimenting with different receivers and amplifiers powered by "free energy", it was found that it is more convenient to connect the audio amplifier to the receiver by using only two wires for audio signals and supply voltage. This would allow to use the radio receiver with no switches, just connecting headphones to the output of the recei
Non-Contact AC Mains Voltage Detector
The circuit diagram of the non-contact voltage detector is shown on the figure 1. It consist of two parts - the AC amplifier and the audio oscillator, based on the Schmitt trigger DD1. 1 of IC CD4093 with the network R7C2, which determines the frequency of the audio signal, generated by piezoelectric buzzer BF1. When the antenna WA1 is located near
Radio and communication circuits 1
Radio and communication circuits 2
Sensitive envelope detector circuit diagram
This is a very sensitive envelope detector for AM radio. The circuit (see Fig. 1) provides linear detection of weak signals with modulation depth of 80. 85% The first stage (VT1) is a common-emitter amplifier circuit for input signals, the second stage is an emitter-follower circuit (VT2). The transistor VT2 operates at low current because of...
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...
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