New Circuits Page 221
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The transmitter was designed specifically for use by radio amateurs as a radio beacon. As such, it provides a good-quality ..
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Everybody likes re-discovering something they did years ago. Here`s a game we all played at school. Possibly under the name of HANG THE BUTCHER. The game is quite simple. One player thinks of a word and writes down the number of letters in that word in the....
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The blinking or flashing rate is determined by Ul, a 555 timer integrated circuit. Its output, at pin 3, feeds U2, a HI1J triac driver. That driver consists of an infrared LED that is coupled internally to a light-activated silicon bilateral switch (DIAC).....
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Switching diodes are used to fire the neon lamps when negative-peak modulation hits 50. 60, and 100%. To use the circuit, keep an eye on the lamps. ..
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Typical stepper-motor control circuits use either logic gates and flip-flops or shift registers to generate the proper sequences of binary codes that produce bidirectional stepper-motor movement. A conventional stepper-motor-control circuit uses a....
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A unit which is often very useful, if we need to isolate, in sound circuits, two stage between them. Then we can use this circuit which has an amplified unit, which gain X1, we do not use total negative feedback, only local, with the result that distortion....
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As a keen cyclist I am always looking for ways to be seen at night. I wanted something that was a novelty and would catch the motorists eye. So looking around at my fellow cyclists rear lights, I came up with the idea of 'NITE-RIDER'. NINE extra bright....
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This Power Supply is suitable for the Modular Burglar Alarm. However, it has other applications. It is designed to provide an output of 12-volts, with a current of up to 1-amp. In the event of mains failure, the back-up battery takes over automatically. When....
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Circuit oscillates because the transistor shifts the phase of the signal 180° from the base to the collector. Each of the RC networks in the circuit is designed to shift the phase 60° at the frequency of oscillation for a total of 180°..
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This circuit charges the battery at 75 mA battery can be left in the charger indefinitely, until the battery is charged, then it reduces the To set the shut-off point, connect a 270-ohm, current to a trickle rate..
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The circuit monitors the input to the microprocessor 5 V regulated supply for voltage drops and initiates a reset sequence before supply regulation is lost. In operation, the resistor capacitor combination Rs and Cj form a short time constant smoothing....
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Using a simple 741 amplifier connected as a current-to-voltage converter with the LED as the current source, the voltage at the output is proportional to incident light. The junction is Q biased only by the difference between the output summing node junction....
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Both ac and dc motors in modern industrial systems often receive their control from PLCs (programmable-logic controllers) in a control room safely away from the process. If an operator must manually set the motor speed while observing the process, the....
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Antenna is the means by which a wireless operator puts his signal into the space and also through which he picks up the signals of the stations with which he wants to communicate. Hence after having a good Receiver and a Transmitter (or Transceiver), the....
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An ultrasonic, or sonar, range finder is a common sensor in robotic systems and industrial environments. Even home and automotive uses are possible. A novel sensor design consists of a WC, a few peripheral components, and a pair of ultrasonic transducers....
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This circuit will generate an ear-splitting 110 dB from 9 V. The setup uses a single 74C14 (CD40106B) CMOS hex inverting Schmitt-trigger IC, wliich must be used with a piezoelectric device with a feedback terminal. The feedback terminal is attached to a....
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A DC motor reversing circuit using non latching push button switches. Relays control forward, stop and reverse action, and the motor cannot be switched from forward to reverse unless the stop switch is pressed first...
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The AD537 uses its two reference outputs—one fixed at 1 V, the other of which varies with temperature (1 mV per °K). At ..
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The circuit in Figure 1 provides ±18 to ±20V adjustable LCD bias voltages with 1% tracking accuracy. The circuit operates from a single 4.2 to 2.5V Li-ion cell for portable monochrome LCD applications. The circuit comprises two blocks: a negative-bias supply....
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This page contains some information on circuits which can be used for triggering stroboscopes from external circuits. The circuit here are designed to be integrate to strboscope circuits so that they can triggered using external trigger pulse. The standard....
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Using an Intersil ICL8038, this function generator generates frequencies from 1 Hz to over 80 kHz. Rl is the fine freque..
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This circuit is basically simple and easy to build, it uses two transistors as active components and a few passive components like resistors, capacitors and two LEDs.
The circuit makes use of the MPS2222 transistor. You can use any NPN type transistor as....
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The above circuit is a precision voltage source, and contains a temperature sensor with a negative temperature co?ficient. Meaning, whenever the surrounding or battery temperature increases the voltage will automatically decrease. Temperature co?ficient for....
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You use high-side current monitoring in many battery-powered products that require accurate monitoring of load current, charger current, or both. In applications for nonportable designs, high-side-current monitoring serves as a power-supply watchdog that can....
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This deceptively simple sequencer actually pulse width modulates the LEDs as it fades from one LED to the next. Bulbs will last much longer when driven in this gentle manner. Add MOSFETs or transistors to the outputs if you wish to drive bulbs. You can....
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This may be the simplest LED flasher circuit you can build, with the notable exclusion of LED's with integrated flashing circuits. This might be a good replacement for the LM3909 in some applications. Take a close look. Only the emitter and collector leads....
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An AC millivoltmeter - calibrated in dB - with a range of 30V down to 3mV full scale (80dB range) would be extremely useful. Attach a microphone (electret mic capsules are quite good), and you have a relative sound level meter, even better if you have some....
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The circuit letsyou convert a serial pulse stream or sinusoidal input to a sinusoidal output at 1/32 the frequency. By varying the frequency of Vrn, you can achieve an output range ofl07:1-from about 100 kH2 to less than 0.01 H2. The output resembles that....
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Conversion of triangle wave shapes to sinusoids is usually accomplished by diode-resistor shaping networks, which accurately reconstruct the sine wave segment by segment. Two simpler and less costly methods may be used to shape the triangle waveform of the....
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A Direct Injection (or DI) box is a very handy piece of equipment for any public address rig or recording studio, whether for band or general use. It will allow you to connect the output from guitar amps, keyboard mixers, tape machines and just about....
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The receiver is an audio amplifier fed by SPKR1, a piezo speaker that is used as a microphone. A scope or headphone..
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Tl and T2 are 600 to 8 ohm transformers (any transistor radio output transformers with 500 to 4 ohm impedance may be used). Ql is a 2N2222 npn transistor, and Q2 is a 2N2907 pnp transistor. Dl and D2 1N270 signal diodes (HEP 134 or 135). Two transistors,....
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The circuit consists of Ql—a phototransistor that responds to an intensity of amplitude-modulated IR light source—and a three-stage, high-gain audio amplifier. Transformer Tl is used to match the output impedance of the receiver to today's popular....
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Lithium Polymer Batteries are a very common source of power today. Many electronics gadgets have one inside, and they have some reasonable features. I've bought great batteries, with different sizes and capacities for my electronics projects. So long I'm....
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This oscillator uses standard inverters, one resistor and one capacitor, and has no minimum operating frequency. R and C must be chosen such that currents into the gates are below recommended operating limits and that leakage current into the gates and into....
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This is a simple - easy to build - transistor based motorcycle alarm. It`s designed to work at 12-volts. But - if you change the relay for one with a 6-volt coil - it`ll protect your "Classic Bike". The standby current is virtually zero - so it won`t drain....
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Three audio circuits are combined in the circuit shown. Each input is coupled to its own level potentiometer (Rl, R2, or R3) an..
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The circuit constitutes a natural extension of Mic-Line balance unit, but can be adapted to any other audio circuit. It is made up of two units in the series : A) A classic unit bass/ Treble and B) a parametric unit of mid frequencies. Both units can also be....
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Input signals from the power line are coupled through C23 and R19 to the input filter network. C23 must be rated at 600 volts. Switch 52 is used as an attenuator. Components C2 through C7, L1 through L3, R1, and R20 form a triple-tuned bandpass filter....
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The amplifier uses a grounded grid circuit with either the Eimac 3CX1000A7 or 8877, ceramic/metal triodes intended for linear service in the HF and VHF ranges. The amp provides the legal power output of 1500 watts PEP and CW service with no effort and....
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The dc motor is used as a generator with the voltage output being proportional to its rpm. The LTC1042 monitors the voltage output and provides the following control functions. If generator voltage output is below 13.8 V, the control circuit is active and....
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This simple variable power supply circuit has a low production cost and delivers an output voltage between 1,5 V and 15 V with a 500 mA maximum current. Its stabilization is better than 2% if the current consumption do not exceed 350 mA. The variation of the....
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A dc-dc converter using a 74HC04 drives Tl. Tl is a ferrite-core transformer using a Fair-Rite, Inc. P/N 597..
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Monitoring a flame and directly switching a 120-V load is easily accomplished using the Ll4G1 for point sources of light. For light sources which subtend over 10° of arc, the L14C1 should be used and the illumination levels raised by a factor of 5. ..
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This circuit was designed as an aid in parking the car near the garage wall when backing up. LED D7 illuminates when bumper-wall distance is about 20 cm., D7+D6 illuminate at about 10 cm. and D7+D6+D5 at about 6 cm. In this manner you are alerted when....
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Unijunction transistors are very intresting. They love to be used in oscillators, and it doesn't takes too many part or very much coaxing to get their sawtooth outputs. This litle squealer will tell you how much voltage it'a connected to. The higher the....
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Cell phones and PDAs are approaching the limit for small form factors, but their feature sets are growing with new functions such as built-in cameras and even video cameras. The initial in-phone cameras were basic, low resolution devices with little in the....
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Contact bounce in those relays, however, can prove troublesome to downstream circuitry. One approach to contact bounce combines a relay with a hot-swap controller. Such controllers are increasingly popular as the means for switching system components without....
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This circuit controls a load (in this case a dc brushless fan) based on a temperature compared with a setpoint. THe transduced is a diode in the forward polarization regime. In fact when forward biased, the forward voltage drop accross a diode has a....
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The circuit input is taken from the terminal loudspeaker or amplifier output jacks. If the right channel is large enough to charge C1 to a potential which exceeds the breakdown voltage of the emitter of Ql, a voltage pulse appears in R7. Similarly, if the....
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A JFET (Ql) serves as the oscillator. D2 helps to stabilize the transistor by limiting positive sinewave peaks and stabilizing the bias. Output from Ql is supplied to a class A buffer, Q2. It operates as a broadband amplifier by means of Tl, which is....
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Most small portable radios require a 3-V supply, which is normally provided by two AA or AAA batteries..
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The figure shows two TL3103 linear Hall-effect devices used for detecting the angle of rotation. The TL3103s are centered in the gap of a U-shaped permanent magnet. The angle that the south pole makes with the chip face of unit #1 is defined as angle 0.....
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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....
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Personal Safes are revolutionary locking storage cases that open with just the touch of your finger. These products are designed as secure storage for medications, jewelry, weapons, documents, and other valuable or potentially harmful items.These utilize....
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A simple circuit to connect the Dreamcast console to PC. No MAXxxx IC required. Only a few discrete components. This circuit is a direct replica of the daVinci cradle schematic:..
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The circuit illustrates a way to power CMOS ICs from RS-232C lines. The MAX680 is normally used to genera..
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The LT®1937 is a step-up DC/DC converter specifically designed to drive white LEDs with a constant current. The device can drive two, three or four LEDs in series from a Li-Ion cell. Series connection of the LEDs provides identical LED currents resulting in....
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This 1-cable system carries composite video (NTSC, PAL, or SECAM), power, and channelselect signals. The interfa..
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Stethoscopes are not only useful for doctors, but home mechanics, exterminators, spying and any number of other uses. Standard stethoscopes provide no amplification which limits their use. This circuit uses op-amps to greatly amplify a standard stethoscope,....
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A strap-down inertial-navigation system uses silicon sensors to measure displacement without entailing the bulk and expense of moving parts or GPS receivers. For example, a three-axis accelerometer and three angular-rate sensors can determine the position....
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Ail ultrasonic cleaner is useful to clean certain items. This circuit uses a microcontroller to control timing and give a digital readout, but only the basic oscillator can be used, if desired. RESL, RES2 are piezoelectric transducers driven by power....
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Reverse engineered circuit diagram of a motor speed regulator out of a portable pocket tape recorder containing a single motor for all functions. This circuit works amazingly well, keeping the motor speed constant regardless of shaft load and battery voltage...
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A keypad enters a four-digit access code, which is programmed via jumpers on a 24-pin plug-in header and socket. Ul is a..
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This circuit uses a programmable op amp such as the -HA2730-a two-amplifier monolithic chip with independent programming ports for each amplifier-whose slew rate and other parameters vary linearly with a so-called set current. The converter circuit uses....
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This receiver weighs about 6 g, used in 41 and 72 MHz, met a great success with readers of the magazine. The RX22 is the subject of these lines is improved RX20. Adding a preamp-HF improving sensitivity. Establishment of an automatic gain control of this....
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TR1 provides a constant current to a bank of three zener diodes, thus maintaining a constant voltage independant of supply voltage variations. The resistor Rx is used to sense the PSU output current and to switches off the current to the zener diodes should....
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To program some AVR microcontroller unit (MCU) you will need an AVR programmer. The better way to do that, is to buy some development kit like STK-500. This kit have the advandage to give you serial port, LCD connector, SRAM socket, 8 switches, 8 LEDs,....
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The SN75604, with input control logic but requiring only one supply rail, can be used in the "lights on" sensor and alarm driver. The device Vqq and enable inputs are connected to a voltage lead from the light switch. The direction control input is connected....
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Presented circuit is very simple. With more sampling, I refrained from using the converter and lamp designed for powering three NiCd or NiMH batteries. Because the voltage difference between the battery and the LED is very small, this arrangement is....
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A TTL counter, an 8-channel analog multiplexer, and a fourth-order low-pass filter can generate 10- to 25-kHz sine waves with a THD better than -80 dB. The circuit cascades the two second-order, continuous-time Sallen-Key filters within ICS to implement the....
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The HA-4900 series comparators can be used as versatile logic interface devices, as shown in these circuits. Negati..
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An operational amplifier can be used as a convenient device for analog comparator applications that require two different trip points. The addition of a positiverfeedback network introduces a precise variable hysteresis into the usual comparator switching....
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A Simple design based on a 555 to Drive a Car Ignition Coil. I Designed this for a Small Electric Fence to Protect my Vegitable Garden from some Small Animal called a Marmots. Last year they ate one of my crops entirely before I could install this device. A....
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The reference current is fed from the supply voltage via Rl, to the inverting terminal, and the variable (noninver..
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The automobile delayed kill switch is simple in concept. When you get out of your car, a secretly located pushbutton switch is pressed. Nothing apparently happens, but at the end of a predetermined time, a relay is pulled in and locked. When the relay is....
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The resistance of loudspeakers is characterized in a frequency depending on the destination and their press. Loudspeakers are distinguished, as for the destination, in loudspeakers of low frequencies, woofer intermediate, mid-range and high tweeter. Their....
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Has an input resistance of 1-MO, a bandwidth from de to about 35 MHz, and a gain of 10 times. Lowfrequency gain is provided by a CA3130 BiMOS op amp operated as a single-supply amplifier. High-frequency gain is provided by a 40673 dual-gate MOSFET. ..
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Using one current source for tbe charge and discharge path in this circuit ensures identical rise and fall times at the capacitor terminal. A Darlington pair ensures identical biasing of the IC during the charge and discharge cycles. The period of the....
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The circuit is designed around the Intersil 8038CC. Frequency range is approximately 20 Hz to 20 kHz—a tuning range of 1000:1 with a single control. The output frequency depends on the value of C2 and on the setting of potentiometer Rl. Other values of C2....
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The oscillator section uses three sections of a 7400 quad NAND gate integrated circuit. The 1-MHz signal from the oscillator is fed into a 7 490 decade counter configured to divide by ten, providing the 100kHz signal. To obtain the 50 and 25kHz outputs,....
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This circuit was used to stop all the BFO drift. The circuit is extremely stable. Turn the receiver off, and then on at any time and temperature, the BFO frequency is exactly the same. The resonator is a Murata CSB 455E. Murata's series number is CSBLA_E....
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The first part of this article series discusses commonly known definitions most crucial for high-speed data converters (in this case analog-to-digital converter or short ADCs) used in communications, instrumentation and data acquisition applications. The....
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This circuit is mainly intended to provide common home stereo amplifiers with a microphone input. The battery supply is a good compromise: in this manner the input circuit is free from mains low frequency hum pick-up and connection to the amplifier is more....
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This very simple, low cost oscillator, is built with two CMOS buffer inverters, two capacitors and a variable resistance. The circuit can work with voltages ranging from 4 V up to 18 V. If Cl = C2, the frequency of oscillation.
..
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A dual audio amplifier that will deliver 50 W per channel is shown in the schematic. It includes preamp and tone controls, and also includes a headphone amplifier. ..
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The "Battery Good" checker. When the button is pressed, the green LED will glow if the battery voltage is above the preset threshold. This version has a higher parts count than the "Battery Low" version, but a bonus is that it can drive an LED to be very....
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The chip tester verifies the functionality and timing of a variety of 7400 series integrated circuits. Students taking Digital Logic Design Lab, Use these chips often in their laboratory.
The IC to be tested should be placed on the ZIF socket and the....
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Security is a prime concern in our day-today life. Everyone wants to be as much secure as possible. An access control for doors forms a vital link in a security chain. The microcontroller based Door locker is an access control system that allows only....
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This circuit was designed to control a 32 channel Christmas light
show from the PC serial port. Originally designed with TTL logic,
it has been simplified using CMOS circuits to reduce component
count. It is a fairly simple, reliable circuit that....
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Senses heart pulse by means of an infrared earlobe clip. Reverse engineered circuit diagram of heart pulse sensor circuit board out of a treadmill. Notice that the output is level shifted for use by CMOS logic running on 4.5V regulated down from the 6V....
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About every year I design and build a new clock. This years project is a clock based on an Intel 8008 first generation 8 bit microprocessor. Because it is a fairly unique project Im putting more effort into the documentation. Im also totally opening the....
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The circuit consists of three stages, an electret microphone, an audio amplifier and an RF oscillator.
The electret microphone consists of only two parts - a FET transistor and a plastic diaphragm. There is nothing else inside the case. The 3-leaded FET has....
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This provides bidirectional speed regulation for small motors and requires no tachometer. The voltage th..
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This circuit can drive anLED display with constant current independently of wide power supply voltage changes. It can operate with a power supply range of at least 4V to 30V. With 10M resistances for R2 and R3 and the inverting input of the comparator....
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This circuit typically uses a voltage around 300 volts for the main high voltage supply and needs a low voltage supply of typically 6 to 15 volts. 555 pin connections not shown above: 1 goes to ground / negative of both low and high voltage supplies. 4,8....
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This 4 1/2-digit DVM circuit is built around a Maxim ICL7129ACPL A/D converter and LCD driver. An ICL8069 CCZR 1.2-V band-gap reference diode is used for a voltage reference. S2a-b-c select one of four ranges up to 200 V (maximum). The meter also has a....
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In this circuit, a CMOS inverter, such as the CD4069, is used to convert the open drain Lx output to a signal suitable for driving the gate of an external P MOSFET. The MTP8P03 has a gate threshold voltage of 2.0 V to 4.5 V, so it will have a relatively....
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The difference between these amplified signals is used to set the 's bias and hence Ql Q2 current channel. This Ql forces of V GS at all that is required voltage corresponding to the circuit input and potential output. The capacitor of 2000 pF to Al provides....
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The charger is build around a LM317 (click to download datasheet) adjustable regulator.
The charge starts when a battery is connected between pins JP1-JP4 or JP2-JP4 or JP3-JP4. For example, if a battery is connected to JP1-JP4 pins then the current that....
The transmitter was designed specifically for use by radio amateurs as a radio beacon. As such, it provides a good-quality ..
Everybody likes re-discovering something they did years ago. Here`s a game we all played at school. Possibly under the name of HANG THE BUTCHER. The game is quite simple. One player thinks of a word and writes down the number of letters in that word in the....
The blinking or flashing rate is determined by Ul, a 555 timer integrated circuit. Its output, at pin 3, feeds U2, a HI1J triac driver. That driver consists of an infrared LED that is coupled internally to a light-activated silicon bilateral switch (DIAC).....
Switching diodes are used to fire the neon lamps when negative-peak modulation hits 50. 60, and 100%. To use the circuit, keep an eye on the lamps. ..
Typical stepper-motor control circuits use either logic gates and flip-flops or shift registers to generate the proper sequences of binary codes that produce bidirectional stepper-motor movement. A conventional stepper-motor-control circuit uses a....
A unit which is often very useful, if we need to isolate, in sound circuits, two stage between them. Then we can use this circuit which has an amplified unit, which gain X1, we do not use total negative feedback, only local, with the result that distortion....
As a keen cyclist I am always looking for ways to be seen at night. I wanted something that was a novelty and would catch the motorists eye. So looking around at my fellow cyclists rear lights, I came up with the idea of 'NITE-RIDER'. NINE extra bright....
This Power Supply is suitable for the Modular Burglar Alarm. However, it has other applications. It is designed to provide an output of 12-volts, with a current of up to 1-amp. In the event of mains failure, the back-up battery takes over automatically. When....
Circuit oscillates because the transistor shifts the phase of the signal 180° from the base to the collector. Each of the RC networks in the circuit is designed to shift the phase 60° at the frequency of oscillation for a total of 180°..
This circuit charges the battery at 75 mA battery can be left in the charger indefinitely, until the battery is charged, then it reduces the To set the shut-off point, connect a 270-ohm, current to a trickle rate..
The circuit monitors the input to the microprocessor 5 V regulated supply for voltage drops and initiates a reset sequence before supply regulation is lost. In operation, the resistor capacitor combination Rs and Cj form a short time constant smoothing....
Using a simple 741 amplifier connected as a current-to-voltage converter with the LED as the current source, the voltage at the output is proportional to incident light. The junction is Q biased only by the difference between the output summing node junction....
Antenna is the means by which a wireless operator puts his signal into the space and also through which he picks up the signals of the stations with which he wants to communicate. Hence after having a good Receiver and a Transmitter (or Transceiver), the....
This circuit will generate an ear-splitting 110 dB from 9 V. The setup uses a single 74C14 (CD40106B) CMOS hex inverting Schmitt-trigger IC, wliich must be used with a piezoelectric device with a feedback terminal. The feedback terminal is attached to a....
A DC motor reversing circuit using non latching push button switches. Relays control forward, stop and reverse action, and the motor cannot be switched from forward to reverse unless the stop switch is pressed first...
The AD537 uses its two reference outputs—one fixed at 1 V, the other of which varies with temperature (1 mV per °K). At ..
This page contains some information on circuits which can be used for triggering stroboscopes from external circuits. The circuit here are designed to be integrate to strboscope circuits so that they can triggered using external trigger pulse. The standard....
Using an Intersil ICL8038, this function generator generates frequencies from 1 Hz to over 80 kHz. Rl is the fine freque..
This circuit is basically simple and easy to build, it uses two transistors as active components and a few passive components like resistors, capacitors and two LEDs. The circuit makes use of the MPS2222 transistor. You can use any NPN type transistor as....
The above circuit is a precision voltage source, and contains a temperature sensor with a negative temperature co?ficient. Meaning, whenever the surrounding or battery temperature increases the voltage will automatically decrease. Temperature co?ficient for....
This deceptively simple sequencer actually pulse width modulates the LEDs as it fades from one LED to the next. Bulbs will last much longer when driven in this gentle manner. Add MOSFETs or transistors to the outputs if you wish to drive bulbs. You can....
This may be the simplest LED flasher circuit you can build, with the notable exclusion of LED's with integrated flashing circuits. This might be a good replacement for the LM3909 in some applications. Take a close look. Only the emitter and collector leads....
An AC millivoltmeter - calibrated in dB - with a range of 30V down to 3mV full scale (80dB range) would be extremely useful. Attach a microphone (electret mic capsules are quite good), and you have a relative sound level meter, even better if you have some....
The circuit letsyou convert a serial pulse stream or sinusoidal input to a sinusoidal output at 1/32 the frequency. By varying the frequency of Vrn, you can achieve an output range ofl07:1-from about 100 kH2 to less than 0.01 H2. The output resembles that....
Conversion of triangle wave shapes to sinusoids is usually accomplished by diode-resistor shaping networks, which accurately reconstruct the sine wave segment by segment. Two simpler and less costly methods may be used to shape the triangle waveform of the....
A Direct Injection (or DI) box is a very handy piece of equipment for any public address rig or recording studio, whether for band or general use. It will allow you to connect the output from guitar amps, keyboard mixers, tape machines and just about....
The receiver is an audio amplifier fed by SPKR1, a piezo speaker that is used as a microphone. A scope or headphone..
Tl and T2 are 600 to 8 ohm transformers (any transistor radio output transformers with 500 to 4 ohm impedance may be used). Ql is a 2N2222 npn transistor, and Q2 is a 2N2907 pnp transistor. Dl and D2 1N270 signal diodes (HEP 134 or 135). Two transistors,....
The circuit consists of Ql—a phototransistor that responds to an intensity of amplitude-modulated IR light source—and a three-stage, high-gain audio amplifier. Transformer Tl is used to match the output impedance of the receiver to today's popular....
Lithium Polymer Batteries are a very common source of power today. Many electronics gadgets have one inside, and they have some reasonable features. I've bought great batteries, with different sizes and capacities for my electronics projects. So long I'm....
This oscillator uses standard inverters, one resistor and one capacitor, and has no minimum operating frequency. R and C must be chosen such that currents into the gates are below recommended operating limits and that leakage current into the gates and into....
This is a simple - easy to build - transistor based motorcycle alarm. It`s designed to work at 12-volts. But - if you change the relay for one with a 6-volt coil - it`ll protect your "Classic Bike". The standby current is virtually zero - so it won`t drain....
Three audio circuits are combined in the circuit shown. Each input is coupled to its own level potentiometer (Rl, R2, or R3) an..
The circuit constitutes a natural extension of Mic-Line balance unit, but can be adapted to any other audio circuit. It is made up of two units in the series : A) A classic unit bass/ Treble and B) a parametric unit of mid frequencies. Both units can also be....
Input signals from the power line are coupled through C23 and R19 to the input filter network. C23 must be rated at 600 volts. Switch 52 is used as an attenuator. Components C2 through C7, L1 through L3, R1, and R20 form a triple-tuned bandpass filter....
The amplifier uses a grounded grid circuit with either the Eimac 3CX1000A7 or 8877, ceramic/metal triodes intended for linear service in the HF and VHF ranges. The amp provides the legal power output of 1500 watts PEP and CW service with no effort and....
The dc motor is used as a generator with the voltage output being proportional to its rpm. The LTC1042 monitors the voltage output and provides the following control functions. If generator voltage output is below 13.8 V, the control circuit is active and....
This simple variable power supply circuit has a low production cost and delivers an output voltage between 1,5 V and 15 V with a 500 mA maximum current. Its stabilization is better than 2% if the current consumption do not exceed 350 mA. The variation of the....
A dc-dc converter using a 74HC04 drives Tl. Tl is a ferrite-core transformer using a Fair-Rite, Inc. P/N 597..
Monitoring a flame and directly switching a 120-V load is easily accomplished using the Ll4G1 for point sources of light. For light sources which subtend over 10° of arc, the L14C1 should be used and the illumination levels raised by a factor of 5. ..
This circuit was designed as an aid in parking the car near the garage wall when backing up. LED D7 illuminates when bumper-wall distance is about 20 cm., D7+D6 illuminate at about 10 cm. and D7+D6+D5 at about 6 cm. In this manner you are alerted when....
Unijunction transistors are very intresting. They love to be used in oscillators, and it doesn't takes too many part or very much coaxing to get their sawtooth outputs. This litle squealer will tell you how much voltage it'a connected to. The higher the....
This circuit controls a load (in this case a dc brushless fan) based on a temperature compared with a setpoint. THe transduced is a diode in the forward polarization regime. In fact when forward biased, the forward voltage drop accross a diode has a....
The circuit input is taken from the terminal loudspeaker or amplifier output jacks. If the right channel is large enough to charge C1 to a potential which exceeds the breakdown voltage of the emitter of Ql, a voltage pulse appears in R7. Similarly, if the....
A JFET (Ql) serves as the oscillator. D2 helps to stabilize the transistor by limiting positive sinewave peaks and stabilizing the bias. Output from Ql is supplied to a class A buffer, Q2. It operates as a broadband amplifier by means of Tl, which is....
Most small portable radios require a 3-V supply, which is normally provided by two AA or AAA batteries..
The figure shows two TL3103 linear Hall-effect devices used for detecting the angle of rotation. The TL3103s are centered in the gap of a U-shaped permanent magnet. The angle that the south pole makes with the chip face of unit #1 is defined as angle 0.....
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....
Personal Safes are revolutionary locking storage cases that open with just the touch of your finger. These products are designed as secure storage for medications, jewelry, weapons, documents, and other valuable or potentially harmful items.These utilize....
A simple circuit to connect the Dreamcast console to PC. No MAXxxx IC required. Only a few discrete components. This circuit is a direct replica of the daVinci cradle schematic:..
The circuit illustrates a way to power CMOS ICs from RS-232C lines. The MAX680 is normally used to genera..
The LT®1937 is a step-up DC/DC converter specifically designed to drive white LEDs with a constant current. The device can drive two, three or four LEDs in series from a Li-Ion cell. Series connection of the LEDs provides identical LED currents resulting in....
This 1-cable system carries composite video (NTSC, PAL, or SECAM), power, and channelselect signals. The interfa..
Stethoscopes are not only useful for doctors, but home mechanics, exterminators, spying and any number of other uses. Standard stethoscopes provide no amplification which limits their use. This circuit uses op-amps to greatly amplify a standard stethoscope,....
Ail ultrasonic cleaner is useful to clean certain items. This circuit uses a microcontroller to control timing and give a digital readout, but only the basic oscillator can be used, if desired. RESL, RES2 are piezoelectric transducers driven by power....
Reverse engineered circuit diagram of a motor speed regulator out of a portable pocket tape recorder containing a single motor for all functions. This circuit works amazingly well, keeping the motor speed constant regardless of shaft load and battery voltage...
A keypad enters a four-digit access code, which is programmed via jumpers on a 24-pin plug-in header and socket. Ul is a..
This circuit uses a programmable op amp such as the -HA2730-a two-amplifier monolithic chip with independent programming ports for each amplifier-whose slew rate and other parameters vary linearly with a so-called set current. The converter circuit uses....
This receiver weighs about 6 g, used in 41 and 72 MHz, met a great success with readers of the magazine. The RX22 is the subject of these lines is improved RX20. Adding a preamp-HF improving sensitivity. Establishment of an automatic gain control of this....
TR1 provides a constant current to a bank of three zener diodes, thus maintaining a constant voltage independant of supply voltage variations. The resistor Rx is used to sense the PSU output current and to switches off the current to the zener diodes should....
To program some AVR microcontroller unit (MCU) you will need an AVR programmer. The better way to do that, is to buy some development kit like STK-500. This kit have the advandage to give you serial port, LCD connector, SRAM socket, 8 switches, 8 LEDs,....
The SN75604, with input control logic but requiring only one supply rail, can be used in the "lights on" sensor and alarm driver. The device Vqq and enable inputs are connected to a voltage lead from the light switch. The direction control input is connected....
Presented circuit is very simple. With more sampling, I refrained from using the converter and lamp designed for powering three NiCd or NiMH batteries. Because the voltage difference between the battery and the LED is very small, this arrangement is....
A TTL counter, an 8-channel analog multiplexer, and a fourth-order low-pass filter can generate 10- to 25-kHz sine waves with a THD better than -80 dB. The circuit cascades the two second-order, continuous-time Sallen-Key filters within ICS to implement the....
The HA-4900 series comparators can be used as versatile logic interface devices, as shown in these circuits. Negati..
An operational amplifier can be used as a convenient device for analog comparator applications that require two different trip points. The addition of a positiverfeedback network introduces a precise variable hysteresis into the usual comparator switching....
A Simple design based on a 555 to Drive a Car Ignition Coil. I Designed this for a Small Electric Fence to Protect my Vegitable Garden from some Small Animal called a Marmots. Last year they ate one of my crops entirely before I could install this device. A....
The reference current is fed from the supply voltage via Rl, to the inverting terminal, and the variable (noninver..
The automobile delayed kill switch is simple in concept. When you get out of your car, a secretly located pushbutton switch is pressed. Nothing apparently happens, but at the end of a predetermined time, a relay is pulled in and locked. When the relay is....
The resistance of loudspeakers is characterized in a frequency depending on the destination and their press. Loudspeakers are distinguished, as for the destination, in loudspeakers of low frequencies, woofer intermediate, mid-range and high tweeter. Their....
Has an input resistance of 1-MO, a bandwidth from de to about 35 MHz, and a gain of 10 times. Lowfrequency gain is provided by a CA3130 BiMOS op amp operated as a single-supply amplifier. High-frequency gain is provided by a 40673 dual-gate MOSFET. ..
Using one current source for tbe charge and discharge path in this circuit ensures identical rise and fall times at the capacitor terminal. A Darlington pair ensures identical biasing of the IC during the charge and discharge cycles. The period of the....
The circuit is designed around the Intersil 8038CC. Frequency range is approximately 20 Hz to 20 kHz—a tuning range of 1000:1 with a single control. The output frequency depends on the value of C2 and on the setting of potentiometer Rl. Other values of C2....
The oscillator section uses three sections of a 7400 quad NAND gate integrated circuit. The 1-MHz signal from the oscillator is fed into a 7 490 decade counter configured to divide by ten, providing the 100kHz signal. To obtain the 50 and 25kHz outputs,....
This circuit was used to stop all the BFO drift. The circuit is extremely stable. Turn the receiver off, and then on at any time and temperature, the BFO frequency is exactly the same. The resonator is a Murata CSB 455E. Murata's series number is CSBLA_E....
This circuit is mainly intended to provide common home stereo amplifiers with a microphone input. The battery supply is a good compromise: in this manner the input circuit is free from mains low frequency hum pick-up and connection to the amplifier is more....
This very simple, low cost oscillator, is built with two CMOS buffer inverters, two capacitors and a variable resistance. The circuit can work with voltages ranging from 4 V up to 18 V. If Cl = C2, the frequency of oscillation. ..
A dual audio amplifier that will deliver 50 W per channel is shown in the schematic. It includes preamp and tone controls, and also includes a headphone amplifier. ..
The "Battery Good" checker. When the button is pressed, the green LED will glow if the battery voltage is above the preset threshold. This version has a higher parts count than the "Battery Low" version, but a bonus is that it can drive an LED to be very....
The chip tester verifies the functionality and timing of a variety of 7400 series integrated circuits. Students taking Digital Logic Design Lab, Use these chips often in their laboratory. The IC to be tested should be placed on the ZIF socket and the....
Security is a prime concern in our day-today life. Everyone wants to be as much secure as possible. An access control for doors forms a vital link in a security chain. The microcontroller based Door locker is an access control system that allows only....
This circuit was designed to control a 32 channel Christmas light show from the PC serial port. Originally designed with TTL logic, it has been simplified using CMOS circuits to reduce component count. It is a fairly simple, reliable circuit that....
Senses heart pulse by means of an infrared earlobe clip. Reverse engineered circuit diagram of heart pulse sensor circuit board out of a treadmill. Notice that the output is level shifted for use by CMOS logic running on 4.5V regulated down from the 6V....
The circuit consists of three stages, an electret microphone, an audio amplifier and an RF oscillator. The electret microphone consists of only two parts - a FET transistor and a plastic diaphragm. There is nothing else inside the case. The 3-leaded FET has....
This provides bidirectional speed regulation for small motors and requires no tachometer. The voltage th..
This circuit can drive anLED display with constant current independently of wide power supply voltage changes. It can operate with a power supply range of at least 4V to 30V. With 10M resistances for R2 and R3 and the inverting input of the comparator....
This 4 1/2-digit DVM circuit is built around a Maxim ICL7129ACPL A/D converter and LCD driver. An ICL8069 CCZR 1.2-V band-gap reference diode is used for a voltage reference. S2a-b-c select one of four ranges up to 200 V (maximum). The meter also has a....
In this circuit, a CMOS inverter, such as the CD4069, is used to convert the open drain Lx output to a signal suitable for driving the gate of an external P MOSFET. The MTP8P03 has a gate threshold voltage of 2.0 V to 4.5 V, so it will have a relatively....
The difference between these amplified signals is used to set the 's bias and hence Ql Q2 current channel. This Ql forces of V GS at all that is required voltage corresponding to the circuit input and potential output. The capacitor of 2000 pF to Al provides....
The charger is build around a LM317 (click to download datasheet) adjustable regulator. The charge starts when a battery is connected between pins JP1-JP4 or JP2-JP4 or JP3-JP4. For example, if a battery is connected to JP1-JP4 pins then the current that....
