Counter Circuits
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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.... -
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....
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This unit would be mounted in a small plastic or preferably metal box, with a 9V battery, level control, a male XLR connector (same as on a mic) and a switch. Current drain is low, since the circuit only uses one dual opamp. There is no need for a high.... -
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.... -
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.... -
I designed a simple sinewave generator based on a Analog Devices AD9832 chip. It will generate a sinewave from 0.005 to 12 MHz in 0.005 Hz steps. That`s pretty good, and definitely good enough for me ! But while waiting for the AD9832 chip to arrive, I came.... -
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.....
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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... -
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....
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This project is basically what I use for a quick prototype, or for just mucking about with an idea. It is easy to make, and only needs a medium size sheet of un-etched printed circuit board (or possibly two). This can usually be obtained from electronics.... -
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....
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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.... -
White noise (the sound you hear when a TV is tuned to a non-existent station) has a frequency characteristic which raises the power level by 3dB with each increasing octave, and is not suitable for response testing (and will probably blow your tweeters as.... -
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.... -
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.... -
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.... -
The circuit is based on a simple inductor-capacitor filter circuit, and needs only a pot and a small light bulb to set and stabilise the oscillation. The frequency is fixed, and with a good inductor should be capable of very low distortion. This circuit is.... -
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....
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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....
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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....
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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....
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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....
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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....
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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.... -
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....
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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,....
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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....
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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....
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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.... -
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....
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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....
New Circuits
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This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of.... -
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.... -
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.... -
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.... -
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.... -
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,.... -
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.... -
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.... -
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.....
Popular Circuits
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