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Yagi Uda Antennas
Metal Detector Circuits
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Voltage Detector Circuits
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Human Sensing Circuits
RF & Radiation
Optical Sensing Circuits
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AC to DC & DC to DC
Solar Cell Circuits
Micro Power Circuits
Switching Power Supplies
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Data Bus Circuits
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RF Converter Circuits
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voltage to frequency
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Video Wall circuits
TV Video Circuits
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8051 / 8052
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H Bridge Circuit
DIY HV Variable Cap
DIY PMA alternator
Interconnection & Timing
Digital Signal Integrity
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Regulated Power Supply
4 Band Resistor
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6 Band resistor
Meter Counter Circuits
LC Resonant Frequency Meter
Recently, I have needed to measure inductances in the hundreds of microhenries to several millihenry range. Though I have a pretty good LRC meter and an excellent bridge on my workbench in Mesa, Arizona, I wanted to make these measurements in my home in Thailand, thus I decided to put something together. The RF Inductance meter on this website...
AVR LED RF Field Strength
Useful as a transmitter tune-up meter or an RF sniffer, this is an RF field strength indicator that is loosely based on the Broad Band RF Field Strength Probe, described elsewhere. It detects RF via a square law detector, basically its a crystal set with gain. The bias circuit for the detector is significantly modified from the probe to reduce...
Digital Volt and Ampere meter
The circuit does not present particular difficulties for somebody that has a small experience. The two circuits are the himself, with a small difference only in their input, when they have they measure voltage or current and in connection that concern decimal point [ dp ]. In the department of input IC1 and IC3, exist the CA3161E, that is a A/D...
50 MHz frequency counter, voltage meter & SWR/PWR indicator
This is a successor of the PIC16C71 4-digit LED f-counter & V-meter. Some hard to find parts used in the previous version, which are out of production for some time, has been omitted. A rather early PIC16C71 has also been replaced by 28-pin device PIC16F876. The later is capable of driving 4 digit LED display in multiplexed mode while...
Simple BER meter is easy to build
A bit-error-rate (BER) tester is a basic tool for digital-communications measurements. Although many commercial BER testers are available, you can easily design and build an inexpensive version. The scheme in Figure 1 has performance similar to that of a commercial tester but requires you to perform a manual calculation based on displayed data....
Simple Field Strength Meter
This Field Strength Meter is simple and also quite sensitive. It uses an ordinary digital voltmeter to measure RF signal strength up to a few hundred MHz. The multimeter should be set to the lowest dc volts range for maximum sensitivity. This is normally 200mV DC for most meters. The circuit works well at VHF (around 100MHz) and was quite...
Field Strength Meter
This is a wide band signal strength meter circuit which responds to small changes in RF energy, designed to be used for the VHF spectrum and will respond to AM or FM modulation or just a plain carrier wave. This circuit measures radio field strength by converting the signal to DC and amplifying it. This field strength meter was designed for VHF...
Moving-coil meter measures low-level currents
Large moving-coil meters may require significant amounts of current for full-scale deflection, and using a shunt resistor may prove impractical when the meter current is larger than the current you are measuring. You can solve the problem by driving the meter from a separate power supply (Figure 1). In this example, an 8-in. moving-coil meter...
This is a simple rev-counter which can measure up to 100,000 rpm with method of strobe synchronization. Its usage is easy. Put a marker on the shaft before measureing, light on the shaft by flashing LED and adjust flashing frequency with the potentiometer as keeping the marker still. The rotation will able to be read from scale of the dial. To...
RF POWER METER
This is an image Schematic. No Description available.
Simple RF Power Meter
Many beginners trying out their skill with QRP TX, for the first time have to overcome many problems before they are able to come on the air. On usual complaint is that, every thing is working fine but the signal is not going out. Here is a simple set up which will enable them to measure the out put power of their transmitter. All that they...
Simple circuit serves as milliohmmeter
When I was recently debugging a design, I discovered that a short circuit existed from a ground plane to a power plane. I did not have access to a milliohmmeter or an equivalent tester for locating this type of short circuit. So, I logged onto the Internet to find an easily constructible milliohmmeter. I found the answer in a manufacturer`s data...
Test batteries without a voltmeter
From a high-volume-production point of view of the Design Idea `Test batteries without a voltmeter` (EDN, Nov 9, 2000, pg 167), it is a time-consuming and laborious task to tweak the large number of potentiometers on each of the comparator input references. An alternative to this onerous adjustment chore is to replace all potentiometers with...
Time Domain Reflectometer (TDR)
This circuit is from Tomi Engdahl's page. It describes a nifty little TDR that, when combined with a regular oscilloscope, can be used to find discontinuities on long runs of cables.
Use your printer port as a high-current ammeter
With a few inexpensive components and INT1Ch, you can turn the printer port of your PC into a high-current ammeter. This design`s goal is to make remote high-current measurements, but you can use this technique to remotely measure any other similar analog electrical quantity, such as voltage and charge, at moderate speeds without going for...
Laser Range Finding for robots
The author's articles of months past focus on the application of 32-bit high-powered processors to amateur robotics and more recently applying CPLD technologies to the same. Continuing on this high-tech trend, this article will cover the concepts and implementation of a Real-time Laser Range Finder based on CPLD Processing of NTSC Video for use...
PC Spectrum Analyzer
The spectrum analyzer circuit takes a stereo input and displays a volume by frequency display on a standard PC monitor. Finding the amplitude of a waveform at each frequency and then mapping this to the screen using a discrete number of levels achieve this. To complete this process, four stages are needed. The first stage is the loopback...
This tiny pH-meter is very tiny: 11cm2 including the PSU circuit! I built it for the College Saint Pierre a few years ago. It is based on a circuit developped at the Facultes Notre-Dame de la Paix, Namur, Belgium. I modified several components to allow a smaller power supply (+/-5V instead of +/-12V) which could be used to power the display...
1300 Mhz Frequency meter with prescaler
Having found an u664b prescaler chip (Telefunken) from an old tv-tuner , I decided to build a valid frequency counter using pic16f84 , the prescaler I use is able to divide by 64 every frequency from 30 to 1300 MHZ. The original project is from Peter Halicky but as he used a sab6456 prescaler (divider by 256)
DIGITAL LED AMMETER
Ammeter is a great addition to any Laboratory Power Supply as it will measure the current consumption and help you determine if there are any problems with the circuit that you are building or testing. This amper meter is capable of measuring the current consumption up to 10A with selected 100mA, 10mA and 1mA accuracy, and consumes only about...
High Impedance Voltmeter LM358
This circuit is designed to provide an inexpensive way to to create a High Impedance Voltmeter while making use of an inexpensive analog or digital multimeter. When measuring voltages in high resistance circuits the resistance of the voltmeter itself has an effect on the circuit. For example if the voltage across a 1 megohm resistor is measured...
RC Receiver tester
No Description available.
Continuity Tester II
Our CONTINUITY TESTER gives an audible indication of continuity between the probes so you can keep your eyes on the probe tip. Secondly its response-time is very short so that you can make lots of tests very quickly while listening for the beep. And thirdly it only responds to a definite short circuit or one that has a resistance of 50 ohms or...
This project is exactly what you need. It is simple to construct and can be connected to almost any analogue multimeter. The scales are accurate over each range - certainly good enough to provide you with the value of any capacitor between 1p and 10u. The actual accuracy depends on the tolerance of the components used in the design and since...
Firstly, we will describe the "add-on" version for the 5x7 Display as this is the cheapest version and, quite frankly, it only deserves a few dollars as a piece of test equipment. It`s "all the rage" to have an Electrolytic Tester for servicing equipment and yet I have serviced over 36,000 appliances without one. Possibly it took me a long...
Field Strength Meter
This Field Strength Meter has been specially designed for our FM bugs. It is capable of detecting very low power transmitters and will assist enormously in peaking many of our FM transmitters that have a coil in the output stage that can be adjusted for optimum output.
Field Strength Meter II
This project has 3 features. 1. It`s a Field Strength Meter, 2. A Frequency Meter and, 3. An aid for testing detuned transmitters. Its uses will become clear in a moment but firstly let`s go over the background of a Field Strength Meter. A Field Strength Meter is essential when designing and building transmitters. It provides signal...
LED Power Meter
The LED power Meter is a simple RF detector using diodes to charge a capacitor. The voltage developed across the capacitor is indicated by a multimeter set to a low voltage range. The circuit is soldered together without the need for a PC board, as can be seen in the diagram below and paper clips are used for the positive and negative terminals...
The pre-distortion circuit described here is extremely simple (Figure 1) and only requires one trimmer adjustment, though you`ll need an accurate way to measure THD in order to achieve the best results. A dedicated distortion analyzer to help you adjust the linearizer circuit is shown later in this article. This analyzer has turned out to be one...
Galvanic decoupling of I2C bus
Since the speed of the I2C bus can be rather high, it is recommended to use a fast optocoupler. However, this circuit will not work on speeds higher then 10KHz. A 6N139 will do the job in all cases. The two PNP and the two NPN transistors can be any standard type, e.g. 2N2219 and 2N2222 (USA) or BC547 and BC557 (EUROPE).
A low resistance ( 0.25 - 4 ohm) continuity tester for checking soldered joints and connections. This simple circuit uses a 741 op-amp in differential mode as a continuity tester. The voltage difference between the non-inverting and inverting inputs is amplified by the full open loop gain of the op-amp. Ignore the 470k and the 10k control for...
EM Field Probe with Meter
This tester is designed to locate stray electromagnetic (EM) fields. It will easily detect both audio and RF signals up to frequencies of around 100kHz. Note, however that this circuit is NOT a metal detector, but will detect metal wiring if it conducting ac current. Frequency response is from 50Hz to about 100kHz gain being rolled off by the...
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...
DIY HV Variable Capacitor
DIY PMA Alternator Plans
Digital Signal Integrity