Vacuum Tubes Valves
Musical & effects
Yagi Uda Antennas
Metal Detector Circuits
Liquid Sensing Circuits
Light Sensing Circuits
Voltage Detector Circuits
Air-Gas Detection Circuits
Human Sensing Circuits
RF & Radiation
Optical Sensing Circuits
Free Energy Circuits
AC to DC & DC to DC
Solar Cell Circuits
Micro Power Circuits
Switching Power Supplies
Light Laser LED
Digital to Analog
Analog to Digital
Data Bus Circuits
Voltage to Pulse
Current to Voltage
Frequency to Voltage
RF Converter Circuits
Sine to Square Wave
Voltage to Current
voltage to frequency
Period to Voltage
Video Wall circuits
TV Video Circuits
Motor Control Circuits
8051 / 8052
PCB CAD Software
Car bike Circuits
555 Timer Circuits
Remote Control Toy
H Bridge Circuit
DIY HV Variable Cap
DIY PMA alternator
Interconnection & Timing
Digital Signal Integrity
Digital & Bipolars
Sensors & Detectors
Regulated Power Supply
4 Band Resistor
5 Band resistor
6 Band resistor
Meter Counter Circuits
Measure temperature in remote locations
The compact and low-power temperature-to-frequency converter in Figure 1 is ideally suited for measuring temperature in remote locations. An AD22100A temperature sensor generates a voltage proportional to the ambient temperature. This voltage then drives an AD7740 VFC (voltage-to-frequency converter), which in turn generates a digital pulse train.
Method simplifies testing high-Q devices
The design of low-phase-noise oscillators requires careful attention to resonator unloaded Q. In the construction of a low-phase-noise, high-frequency oscillator, the goal is to achieve an unloaded-Q figure greater than 400 in a reasonable package. Also, you need to monitor the effect of the package and pc-board arrangement.
Simple method tests cables
This method is sometimes impractical, however, because it cannot check for short circuits. The method shown in Figure 1 solves the short-circuit problem. Connecting LED indicators at each shorting loop provides a visual indication. The beauty of this scheme is that any short circuit causes at least one LED to extinguish. You can then diagnose...
Build a Microphone Polarity Tester
Many things can go wrong in a modern recording studio, but few are as difficult to track down as reversed microphone polarity. When a microphone is placed in front of a sound source, a positive pressure on its diaphragm caused by forward-moving air results in a positive voltage on one of its output pins and a negative voltage on the other. But...
Simple MIDI interface tester
Sometimes when experimenting with different soundcards and MIDI interfaces it is useful to see if there is some data going in MIDI interface. This can be easily tested with this adapter, which converts the midi signals to visible light pulses. Just the circuit and plug it to the MIDI output of your computer. When computer sends any midi data...
Missing-codes tester checks 16-bit ADC in 7 sec
As the resolution of ADCs increases from 12 to 16 bits and higher, the difficulty in testing the "no- missing-codes" specification grows proportionately. To fully guarantee no missing codes for a 16-bit ADC requires testing all 2161 possible output codes. Undertaking such a production test could add much extra cost to the ADC without a quick...
Multi Wire Cable Tester
A multi wire cable tester with a separate LED for each wire. Will show open circuits, short circuits, reversals, earth faults, continuity and all with four IC`s. Designed initially for my intercom, but can be used with alarm wiring, CAT 5 cables and more.
Noncontact device tests power supplies
The probelike device in Figure 1 comes in handy as a quick go-no-go test for step-down power supplies. You can build it using a very bright surface-mount LED and an inductor of the same type as in the power supply, which in this case is 100 µH. Placing this probe close to a working step-down power-supply coil lights the LED. The probe lights...
PC hardware monitor reports the weather
You usually use PC hardware monitors to keep a close eye on power-supply voltage levels, the speed of system cooling fans, and even the temperature of the CPU. Until fairly recently, this level of system monitoring was reserved for high-end servers running mission-critical applications. However, now that low-cost hardware monitoring ASICs are...
PIC frequency counter with prescaller
This is an image Schematic. No Description available.
LOGIC PROBE with PULSER
This project is a combination Logic Probe and Logic Pulser. It is capable of testing all sorts of digital and microcomputer projects. You will find it extremely handy when designing a project as the golden rule is to test everything in steps and stages during the design-and-construction process. If you are not sure how a Logic Probe or...
Simple Polarity Tester
This tester can be used to check the polarity of any power source, and is therefore very useful when installing automotive equipment, alarm systems or anything else you can think of. Because this circuit is so simple and cheap, even frying one with an over voltage is not a big deal.
Pulse-Generator & Signal-Tracer
This simple circuit generates narrow pulses at about 700-800Hz frequency. The pulses, containing harmonics up to the MHz region, can be injected into audio or radio-frequency stages of amplifiers, receivers and the like for testing purposes. A high-pitched tone can be heard from the speaker of the device under test when all is working properly....
Radio Spectrum Monitor
This is an experimental work to monitor a spectrum pattern of radio band, and is a continuous project from Audio Spectrum Monitor. To analyze the spectrum of an input signal, I chose an Atmel`s AVR microcontroller used in Audio Spectrum Monitor to process FFT. When think it easy, it can be thought that sample an input RF signal directly and...
Simple setup tests bit-error rate
Traditionally, the reception quality of a digital receiver is expressed in terms of BER (bit-error rate). This figure is the proportion of received bit errors in a given period. Typically, you measure the BER in the lab by applying an RF signal, modulated by a pseudorandom code, to the receiver under test. This Design Idea suggests an...
Simple circuit detects dc ringing
Ring detection is a common task in telephony-related digital design. The goal is to sense an ac ringing voltage applied to the telephone line by a central office or PBX (private branch exchange) and then pass an appropriate signal to the µC or µP. Figure 1a shows a typical ac-coupled ring-detection circuit. The serially connected capacitor...
Simple emulator speeds testing
Designing and testing embedded hardware can be frustrating if you have to rely on somebody else`s perhaps-unready firmware to test your hardware. Often, hardware is ready for testing before debugging and system firm-ware are available from software developers. Microprocessor emulators are solutions but are often expensive, hard to use, and...
Simple tester checks Christmas-tree lights
Why is it that you always test 48 bulbs before you find the bad one in a 50-light string? The simple circuit in Figure 1 allows you to divide and conquer, greatly reducing the time it takes to find the bad bulb. The circuit uses a pair of NE2 neon bulbs with current-limiting resistors. You can use a pair of Radio Shack 272-1100 bulb-resistor...
Scheme provides automatic power-off for batteries
The circuit in Figure 1 provides a simple and inexpensive way to protect one of the most valuable components in portable applications: the battery. Applications include all portable equipment that requires a limited time of operation, such as test instruments, guitar tuners, and electronic toys. Pressing the on/off momentary switch starts the...
Simple circuit times bathroom fan
Forget to turn off the ceiling fan in your bathroom? Install the simple timer in Figure 1. It`s located out-of-sight in the fan unit, and you turn it on via the wall switch. The circuit costs virtually nothing, using "junk" parts. When ac power appears, a simple rectifier develops approximately 7V across filter capacitor C. This voltage powers...
Sleep-switch cum Wake-up Timer
Here is a sleep-switch circuit that can be easily converted into a wake-up timer. A dual-mode time setting makes the system versatile. The circuit is low-cost and can function as a precise timer.
This timer was designed for people wanting to get tanned but at the same time wishing to avoid an excessive exposure to sunlight. A Rotary Switch sets the timer according to six classified Photo-types (see table). A Photo resistor extends the preset time value according to sunlight brightness (see table).
Temperature monitor measures three thermal zones
You can use an ADT7461 single-channel temperature monitor; an ADG708 low-voltage, low-leakage CMOS 8-to-1 multiplexer; and three standard 2N3906 pnp transistors to measure the temperature of three separate remote thermal zones (Figure 1). Multiplexers have resistance, RON, associated with them; the channel matching and flatness of this...
Trace voltage-current curves on your PC
Some years ago, one of the fundamental electronic instruments was the laboratory curve tracer. A CRT display would sweep out terminal behavior (current versus voltage) from which you could derive mathematical models. Classic presentations of diodes, transistors, and other devices enlightened designers about linear and nonlinear operation. From...
Track multisite temperatures on your PC
The low-cost circuit in Figure 1 allows you to track four remote temperatures with thermistor sensors through the parallel port on your PC. This four-zone thermometer instrument has a temperature range of 40 to +90°C and a resolution of better than ±1°C. You can calibrate its accuracy to within 1°C over a 0 to 50°C span and within 3°C over a 40...
Transistor junction monitors remote temperature
The circuit in Figure 1 uses a regular, general-purpose transistor as the sensing element and a thermal-diode monitor IC to measure temperature. The ADM1021 usually connects to an on-chip thermal diode on a CPU die itself, but in this application the sensor connects to a regulator low-cost discrete npn transistor, the 2N3904. The circuit ties...
TRANSISTOR TESTER & SIGNAL INJECTOR
There have been a lot of transistor tester circuits in recent electronics magazines, but this one is different. It has more features and includes a signal injector so you can test audio sections of radios and the front end of FM transmitters etc. The major advantage with this design is its automatic operation. All you have to do is fit the three...
Transistor tester fits into your pocket
It can be helpful to rapidly and easily determine the polarity (npn or pnp) and function of a transistor. The pocket-transistor tester in Figure 1 is ideal for quickly testing without regard to such parameters as gain and frequency response. You connect the transistor, or device under test, between the collectors, T, of an astable multivibrator....
Transmission line tests 1-kW device using only 100W
A 13.56-MHz, ISM (industrial, scientific, and medical)-band RF-measurement device had the test requirement of a 50-hour, 1-kW burn-in. The device under test needed to be simultaneously stressed at an RF potential and RF current equivalent to 1 kW, but the only spare RF source at hand was a 100W RF generator. Besides, saving energy seemed...
Transmitter accurately transfers voltage input
When you connect remote sensors to a central process controller, a simple, robust, and commonly used interface is the 4- to 20-mA loop. The advantages of this current loop include the simplicity of just two twisted wires that share both power and signal, the loop`s high noise immunity in harsh environments, and the de facto loop standard within...
Ultra-simple Voltage Probe
This circuit is not a novelty, but it proved so useful, simple and cheap that it is worth building. When the positive (Red) probe is connected to a DC positive voltage and the Black probe to the negative, the Red LED will illuminate. Reversing polarities the Green LED will illuminate. Connecting the probes to an AC source both LEDs will go on....
Zener test circuit serves as dc source
This Design Idea describes a versatile test circuit for zener diodes after yet another misread zener diode had infiltrated the ranks of 1N4148 diodes assembled on a pc board. As a bonus, the circuit can serve as a moderate-voltage, power-limited adjustable dc source. Although conventional multimeters` resistance ranges typically apply enough...
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