Top Circuits Page 18
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This circuit uses an SAD 512D (Reticon) chip, which is a 512-stage analog shift register. By varying th..
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A gate voltage is applied to initiate the proceedings. When the gate voltage is in the ON state, Q..
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This bull horn uses U1 as a driver stage and U2 as an output driver. U1 is set up for a gain of 200. The microphone should have a..
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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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Integrated circuit Ul is connected as a low-frequency asymmetrical oscillator. Its output is inverted by Ql and fed to the reset te..
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The electronic bagpipe mimics the sound of real instruments. This circuit uses two UJT oscillators and an amplifier (Q3,..
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As shown, three ICs are used to produce the sounds. ICl is a 555 timer that generates clock pulses. It is configured as an astable multivibrator. The frequency of the clock pulses is set by trim: mer potentiometer PI. These clock pulses are coupled to the....
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The space-age sound device uses a 556 dual-times IC to produce a phasor sound. That IC is actually two 555 timer ICs in one 14-pin package, as shown in the schematic. Each timer inside the 556 is connected iri an astable multivibrator mode. The first timer....
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The electronic gong is comprised of an oscillator (built around half of a 74COON quad 2-input NAND gate), an active twin-T filter (built around a TL081), and will drive an audio amplifier IC such as aii LM386N. Pulses from astable multivibrator ICl cause....
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An outside horn-type speaker works best with the circuit. However, such devices require a great deal of power, so this sounder should only be used in alarm circuits where at least a 6-A SCR is used as the sounder driver. A single CMOS 4001 quad 2-input NOR....
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This is a simple low-level noise maker that`s ideally suited to certain alarm applications. When the sounder is located in another part of the building, the sound level is loud enough to be heard, but is not loud enough to warn off an intruder. A single....
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The circuit consists of four parts: a binary counter, a D/A converter, a VCO, and an audio output amplifier. The speed at which the counter counts depends on the frequency of the output of the VCO, which in turn is determined by the output of the counter.....
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Half of a Motorola MG14538B dual, precision, retriggerable mono stable multivibrator is used to form an extended on-time timer circuit. That type of circuit can be used as a switch debouncer. Such circuits are often used in digital circuitry, where each and....
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The transistors form a differential pair with an active current-source tail. This configuration, known technically as a variable-transconductance multiplier, has an output proportional to the product of the two input signals. Multiplication occurs due to the....
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By adding a small amount of noise to a signal to be digitized (about 0.7 bit): where: n = #..
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This thermometer is capable of 0.01°C accuracy over - 50°C to +150°C. A unique trim arrangement eliminates cumbersome trim interactions so that zero gain, and nonlinearity correction can be trimmed in one even trip. Extra op amps provide full Kelvin....
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TCA965 window discriminator IC allows the potentiometers RVl and RV2 to set up a window height and window width respectively. Rl and thermistor THl for a potential divider connected across the supply lines. Rl is chosen such that at ambient temperature the....
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The circuit exploits the fact that when fed from a constant current source, the forward voltage of a silicon diode varies with temperature in a reasonably linear way. Diode Dl and resistor R2 form a potential divider fed from the constant current source. As....
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This design measures the differential temperature between two sensors. Sensor Tl, located before the heater resistor, assumes the fluid"s temperature before it is heated by the resistor. Sensor TZ picks up the temperature rise induced into the fluid by the....
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Filtered 15 V de is applied to a series circuit consisting of thermistor R2 and parallel combination of resistors Rl and R3. Transistor Ql acts as a switch whose state is determined by the setting of potentiometer R3, which is first set so just enough....
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This circuit responds quickly enough to prevent damage from most overloads. C 1 "s input is connected to the output of the LT1088 servo circuit. If the LT1088 circuit"s output exceeds the threshold at Cl"s other input, C1 trips, discharging the 2-!"F....
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When power is applied, the thermistor, a negative tc device, is at a high value. A1 saturates positive. This forces the LT3525A switching regulator"s output low, biasing Ql. As the heater warms, the thermistor"s value decreases. When itsinputs finally....
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Sensing element Ql is a 2N3904 general-purpose npn transistor, although any general-purpose npn unit in a T0-92 style case will do. IC1, an LM334, supplies Ql with a constant current that is independent of temperature. An LM324 quad op amp, IC2, forms a....
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To decouple the sensors from the meter amplifier, either a reference junction at ooc or a bucking voltage set at room temperature may be used. The latter method is simpler, but is sensitive to changes in ambient temperature. ..
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The temperature sensor provides an input to pin 3 of the NE5037 of 32 mV/°C. This 32 mV is the value of one LSB for the NE5037. The LM334 is a three-terminal temperature sensor and provides a current of 1 p.A for each degree Kelvin. The 32-KO resistor....
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This circuit uses the +5 V reference output and the op amp to level shift and amplify the 2.1 mV/°C Tempco output into a voltage signal dependent on the ambient temperature. Different scaling can be obtained by selecting appropriate resistors from the....
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A simple op amp and silicon diode are the heart of the temperature-to-voltage converter that will permit you to use an ordinary voltmeter-either analog or digital-to measure temperature. User adjustments make it possible for a reading of either 10 mV or....
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This control, with zero-voltage load switching, uses a CA3130 BiMOS op amp and a CA3079 zero-voltage switc..
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A thermistor (RI) is compared with a reference (R2) in a Wheatstone-bridge circuit. Comparator Ul"s output goes high..
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For the absolute measurement of temperatures, a thermometer is indispensable. However, in many situations, an ..
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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 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 output goes high when a preset temperature is exceeded. A fixed half-supply reference voltage feeds a reference..
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As a sensor in the design of this linear thermometer, the LM34 is used. The output is the difference between..
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This thermometer is capable of measuring temperatures from - 30 to +120 °F. A diode-connected 2N3904 transistor form..
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This circuit combines a current source and a platinum RTD bridge to form a complete high-accuracy thermometer. Th..
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A TDA1024 electronic thermostat senses soil temperature via thermistor R6. The circuit uses zero-crossing switching of the heater. The heater is made of elastic-coated steel wire. PI is used to set the temperature. The heater should have 2 or more....
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The telephone-line tester consists of nothing more than a meter (that`s used to measure line voltage in the on- and off-hook state), three resistors (one of which is variable), a pushbutton switch, and a modular telephone connector...
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This circuit provides a linear increase of frequency of 10 Hz/°C over 0-100 °C and can thus be used with logic systems, including microprocessors. Temperature probes Ql Vbe changes 2 mV/°C. This transistor is incorporated in a constant current source....
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This temperature controller operates as a pulse snatching device, which allows it to run at its own speed and tum on at the zero crossing of the line frequency. Zero crossing tum-on reduces the generation of line noise transients. TMOS Power FET, Ql, is....
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The fan employed is one of the new electrostatic type which is very reliable, because it contains no wearing parts. These devices require high-voltage drive. When power is applied, the thermistor, located in the fan"s exhaust stream, is at a high value.....
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Both of these converters use CMOS inverters. Figure 105-1A shows a free-running circuit having both the pulse duration and pulse pause dependent on temperature of the diode D8. It can be used where a synchronization between the converter and something else....
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The ROMs or PROMs must have the correct code for converting the data from the NE5037 -used as address for the ROMs or PROMs-to the appropriate segment driver codes. The displayed amount could easily be converted to degrees Fahrenheit, °F, by the....
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The DVM-to-temperature adapter is built around a single IC, National"s LMlO. That micropower IC contains a stable 0.2 V reference, a reference amplifier and a general-purpose op amp. The circuit is designed for a linear temperature range of 0 to 100°C (32....
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This oscillator circuit includes a quartz crystal that has a nominal resonant frequency of 262,144 Hz and is cut in the orientation that gives a large linear coefficient of frequency variation with the temperature. In this type of circuit, the oscillation....
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This temperature controller has a range of -50 to +150°C and permits defrosting. R7, VR3, and R8 ..
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Using the fact that the VRE of a transistor shifts 59.16 mV per decade of current at 25°C. This cons..
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You need to find a reliable full bridge driver to drive your flyback transformer? Well, This is your final stop. There are many flyback drivers schematics out there,
but most of them will not last for long. It is common known that famous ZVS invented by....
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This circuit provides a regulated dc with less than 100 mV of ripple for microprocessor applications. Necessary operating voltages are taken from the bleeder resistor network connected across the unregulated 28 V supply. The output of the LM710 comparator....
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This low-voltage high-current output, sWitching de power supply is running off the 220-Vac input. In this circuit, an ST2 diac relaxation oscillator, Q3, Cl, and the diac, initiates conduction of the output switching transistor Ql, the on-time of which is....
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The schematic shows a 50W power supply with a 5-V 10-A output. It is a flyback converter operating in the continuous mode. The circuit features a primary side and secondary side controller will full-protection from fault conditions such as overcurrent. ..
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The LTC10432 switched-capacitor building block provides nonoverlapping complementary drive to the Ql to Q4 power MOSFETs. The MOSFETs are arranged so that Cl and C2 are alternately placed in series and then parallel. During the series phase, the + 12 V....
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A simple battery-powered switching regulator provides 5 V outfrom a 9-V source with 80% efficiency and 50 mA output capability. When Q1 is on, its collector voltage rises, forcing current through the inductor. The output voltage rises, causing A1"s output....
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A shows a COR/CAS circuit for repeater use. CR1 is a silicon diode. 2 may be any relay with a 12-V coil (a long-life..
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Switch-mode power supplies offer the benefit of a much greater efficiency than obtainable with a traditional ..
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In conventional applications, switching-regulator ICs regulate VQVT by controlling the current through an external inductor. The IC in A, however, driving a diode-capacitor network in place of the inductor, offers comparable performance for small loads. The....
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The Max650 switching regulator produces a regulated 5 V from large negative voltages, such as the -48 V found on telephone lines. The resulting power supply operates with several external components, including a transformer, and it delivers 250 mA. The....
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The power supply uses two VN4000A 400-V MOSPOWER FETs in a half-bridge power switch configuration. Outputs available are + 5 Vat 20 A and ±15 V (or ±12 V) at 1 A. Since linear three-terminal regulators are used for the low-current outputs, either ±12 V....
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An LT1172 generates positive and negative voltages from a 5-V input. The LT1172 is configure..
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A shows a typical LTC 1148 surface-mount, application providing 5 V at 2 A from an input voltage of 5.5 V to 13.5 V. The operating efficiency, shown in B, peaks at 97% and exceeds 90% from 10 mA to 2 A with a 10-V input. Ql and Q2 comprise the main switch....
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Predictable time delays from as low as 0 milliseconds to over 3 minutes are obtainable without resorting to a large value electrolytic-type timing capacitor..
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Circuit (a) lets you delay the leading edge of a positive pulse while leaving the trailing edge almost unaffected. A positive input transition, inverted hy IC2, has no effect on IC1B. However, when the positive transition reaches IC1A, (delayed hy the....
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A single monostable multivibrator delays a pulse train by a variable amount; nonetheless, this amount can be no less than the minimum allowed pulse width fw· The exclusive-OR gate, IC1, generates a short pulse following every leading or falling edge of....
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You can obtain well over 360° of phase delay by cascading two monostable multivibrators. In a typical configuration, a single monostable multivibrator is used to introduce delay in a pulse train; the multivibrator triggers on each incoming pulse, provided....
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The time delay, T, in seconds is: T = 1.1 x Cl x (Rl + R2). The resistances are in megohms and capacitances in microfarads. The sum of R1 and R2 should not be Jess than 1000 0 nor higher than 20 MO. Pressing S1 starts the timing cycle. A low-going pulse,....
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Power is applied to the circuit with the initiate switch open. The 25-JtF capacitor charges through the A14, or equivalent, diode and 2.2-KO resistor to full supply voltage. When the initiate switch is closed, the low side of the capacitor is suddenly....
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After the first cycle. the relay will normally be energized. When normally closed pushbutton 51 is activated, the SCR turns off, the relay is de-energized, and power is applied to the relaxation oscillator and the load. Mter a time delay varying from....
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The alarm/sensor circuit shown is built around two SCRs, a transistor, a 4049 hex inverter, and a few support components, all of which combine to form a closed-loop detection circuit with a delay feature. The delay feature allows you to enter a protected....
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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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Three 555 IC timers are used in this circuit to construct a simple delayed-pulse generator. IC1 acts as a waveform shaper to produce a rectangular waveform. IC2 produces a delaying pulse to trigger 103 on the trailing edge of the delaying pulse. Rl controls....
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This circuit uses a Hall-effect sensor, consisting of an IC that resides in a small gap in a flux-collector torrid, to measure de current in the range of 0 to 40 A. You wrap the current-carrying wire through the toroid; the Hall voltage VH is then linearly....
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In operation, the TL3019 device will activate, or become low, when a south pole of a magnet comes near the chip face of the device. The example shows five doors. Each door has a magnet embedded in its edge with the south pole facing the outer surface. At....
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Hall-effect switches have several advantages over mechanical and optically coupled switches, They"re insensitive to environmental light and dirt, they don"t bind, and they don"t sustain mechanical wear. Their major drawback is that they require three wires....
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The TL3103 linear Hall-effect device can be used as a compass. By definition, the north pole of a magnet is the pole that is attracted by the magnetic north pole of the earth. The north pole of a magnet repels the north-seeking pole of a compass. By....
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Although not intended for this application, Hall-effect switch can be used as the basis for a rather unusual oscillator. The oscillator can be reconfigured, as shown in Fig. B, to allow the circuit`s oscillating frequency to be controlled via an RC network, ..
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The two probes shown are held in the hands and the skin resistance applies bias to the transistor. The 5 k ohm pot is set for zero deflection on the meter. When the ' 'subject'' is embarrassed or lies, sweating on the hands takes place, increasing the bias....
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The circuit is built around an LM339 quad comparator, Ul, which forms the basis of a Schmitt trigger, timer circuit, and a window comparator. One comparator within the LM339 (pins 1, 7, 6), plus LDR1, R4, R5, R6 and R8, is used as a Schmitt trigger. The....
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This game tests a player"s reaction time. It is activated by closing switch SI, which starts the tone generator and arms the circuit. The touchplate, labeled PLAY in the diagram, consists of two metal strips about l/16th-inch apart. The first player to....
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Six LEDs are arranged to produce a display the same as the dots on a dice. When PBI is depressed, the display is blanked and the oscillator (ICl a, b, c) clocks IC2 at about 1MHz. IC2 counts from zero and resets on seven..
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The 555 timer produces a rapid series of pulses whenever switch SI is open. These pulses are counted in groups of 16 and converted into binary form by the 7493 and applied to the 74154 (a l-of-16 decoder/demultiplexer) wired so that each of its 16 output....
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Circuit uses an astable multivibrator to vary the heads-or-tails condition, and a flip-flop to store the condition given by the multivibrator..
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This is a circuit for a game of the shooting gallery variety. IC2a and b form an astable multivibrator clocking ICl which causes LEDs 1-8 to flash in turn LED 5 is the target LED and the object of the game is to depress PBI just as LED 5 comes on. If this is....
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The circuit is basically a 555 astable circuit that divides two LEDs, LEDl and LED2. LED2 is switched on when the output of Ul is high, and LEDl is activated when its output is low. When Ul oscillates, LEDl and LED2 switch on alternately as the output....
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Using two SCRs, this control circuit is designed to lock out the other SCR when one has been triggered, so only one lamp will light. Indicator lamp Il is controlled by SCRl. The operator simply presses switch Sl. Lamp I2 is similarly controlled by S2....
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The basic die circuit is given. A 555 timer, ICl, is connected as an astable multivibrator. This feeds clock pulses to divide-by-six counter IC2 tbe outputs of which are decoded by gates Nl to N6 to drive an array of LEDs in the familiar die pattern. When....
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This circuit has a rate multiplier using a 4093 Schmitt trigger as an oscillator, driving a 4017 decade counter. When a pulse p..
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This circuit uses a timer to generate pulses at a 5-ms clock rate. The pulses are shifted into the shift register, one at a ..
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This circuit is a 10-LED spinning wheel that "clicks" as the wheel passes each point. The rotation starts fast, then gradu..
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The electromagnetic ring launcher is comprised of.four subcircuits: a clock circuit (built around U5, a 555 oscillator/timer configured for astable operation), a count-down/display circuit (built around U3), a 74190 synchronous up/down counter with BCD....
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Up to eight players each have their own answer button to press, corresponding to the four Red Team and four Green Team LEDs on the master control board. As soon as the first contestant who thinks that he knows the answer presses the button, a loud tone....
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The slot machine`s realistic action is provided by seven ICs and three displays, as shown. Two 555 CMOS timer ICs generate pulses. IC1 is used to generate the clock pulses for the entire electronic slot machine. The pulses are coupled from the output (pin....
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The circuit, uses a two-transistor direct-coupled oscillator that has a frequency determined by CI, R2, and the (skin) resistance across the touch pads. Since CI and R2 are fixed values, only the skin resistance across the touch pads can vary the sound of....
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The persona] message recorder is built around an ISD1016 CMOS voicc messaging system, which does away with the cumbersome and expensive analog-to-digital and digital-to-analog conversion circuits. A functional block diagram of the ISD1016 is shown. The....
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This device prevents paper notes and memos from being overlooked. A paper note placed between two fingers made of a conducting material (metal or conductive plastic) breaks the circuit, allowing pair 1 of Ul-a to go high...
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The signal starts at a low frequency, rises for about 1.15 seconds to a high frequency, ceases for about 0.35 seconds, then starts rising again from a low frequency, and so on ad infinitum.
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A large number of intercom stations can be tied together. All units are connected in parallel, and the entire system is buzzed by only one signaling circuit. Each unit is powered individually from 1.5-V cells for redundancy. For greater signal volume, 3-V....
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The circuit provides a minimum component intercom. With switch SI in the talk position, the speaker of the master station acts as the microphone with the aid of step-up transformer Tl. A turns ratio of 25 and a device gain of 50 allows a maximum loop gain of....
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When activated, the transmitter sends out a 49.890-MHz, AM rf carrier. The.receiver detects, amplifies, and decodes the rf signal, which, in turn, activates a piezo buzzer. The receiver is small enough to carry in a pocket or sit on your workbench. ..
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Amplifier A increases the microphone"s output to a usable level. The output signal is fed to op amp B, which inverts the signal180°. A balance-control potentiometer connects across the outputs of amplifiers A and B. 1f an audio tone is fed into the....
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The design consists of an amplifier, a double-pole changeover switch and two loudspeakers: one for the master station and..
This circuit uses an SAD 512D (Reticon) chip, which is a 512-stage analog shift register. By varying th..
A gate voltage is applied to initiate the proceedings. When the gate voltage is in the ON state, Q..
This bull horn uses U1 as a driver stage and U2 as an output driver. U1 is set up for a gain of 200. The microphone should have a..
The receiver is an audio amplifier fed by SPKR1, a piezo speaker that is used as a microphone. A scope or headphone..
Integrated circuit Ul is connected as a low-frequency asymmetrical oscillator. Its output is inverted by Ql and fed to the reset te..
The electronic bagpipe mimics the sound of real instruments. This circuit uses two UJT oscillators and an amplifier (Q3,..
As shown, three ICs are used to produce the sounds. ICl is a 555 timer that generates clock pulses. It is configured as an astable multivibrator. The frequency of the clock pulses is set by trim: mer potentiometer PI. These clock pulses are coupled to the....
The space-age sound device uses a 556 dual-times IC to produce a phasor sound. That IC is actually two 555 timer ICs in one 14-pin package, as shown in the schematic. Each timer inside the 556 is connected iri an astable multivibrator mode. The first timer....
The electronic gong is comprised of an oscillator (built around half of a 74COON quad 2-input NAND gate), an active twin-T filter (built around a TL081), and will drive an audio amplifier IC such as aii LM386N. Pulses from astable multivibrator ICl cause....
An outside horn-type speaker works best with the circuit. However, such devices require a great deal of power, so this sounder should only be used in alarm circuits where at least a 6-A SCR is used as the sounder driver. A single CMOS 4001 quad 2-input NOR....
This is a simple low-level noise maker that`s ideally suited to certain alarm applications. When the sounder is located in another part of the building, the sound level is loud enough to be heard, but is not loud enough to warn off an intruder. A single....
The circuit consists of four parts: a binary counter, a D/A converter, a VCO, and an audio output amplifier. The speed at which the counter counts depends on the frequency of the output of the VCO, which in turn is determined by the output of the counter.....
Half of a Motorola MG14538B dual, precision, retriggerable mono stable multivibrator is used to form an extended on-time timer circuit. That type of circuit can be used as a switch debouncer. Such circuits are often used in digital circuitry, where each and....
The transistors form a differential pair with an active current-source tail. This configuration, known technically as a variable-transconductance multiplier, has an output proportional to the product of the two input signals. Multiplication occurs due to the....
By adding a small amount of noise to a signal to be digitized (about 0.7 bit): where: n = #..
This thermometer is capable of 0.01°C accuracy over - 50°C to +150°C. A unique trim arrangement eliminates cumbersome trim interactions so that zero gain, and nonlinearity correction can be trimmed in one even trip. Extra op amps provide full Kelvin....
TCA965 window discriminator IC allows the potentiometers RVl and RV2 to set up a window height and window width respectively. Rl and thermistor THl for a potential divider connected across the supply lines. Rl is chosen such that at ambient temperature the....
The circuit exploits the fact that when fed from a constant current source, the forward voltage of a silicon diode varies with temperature in a reasonably linear way. Diode Dl and resistor R2 form a potential divider fed from the constant current source. As....
This design measures the differential temperature between two sensors. Sensor Tl, located before the heater resistor, assumes the fluid"s temperature before it is heated by the resistor. Sensor TZ picks up the temperature rise induced into the fluid by the....
Filtered 15 V de is applied to a series circuit consisting of thermistor R2 and parallel combination of resistors Rl and R3. Transistor Ql acts as a switch whose state is determined by the setting of potentiometer R3, which is first set so just enough....
This circuit responds quickly enough to prevent damage from most overloads. C 1 "s input is connected to the output of the LT1088 servo circuit. If the LT1088 circuit"s output exceeds the threshold at Cl"s other input, C1 trips, discharging the 2-!"F....
When power is applied, the thermistor, a negative tc device, is at a high value. A1 saturates positive. This forces the LT3525A switching regulator"s output low, biasing Ql. As the heater warms, the thermistor"s value decreases. When itsinputs finally....
Sensing element Ql is a 2N3904 general-purpose npn transistor, although any general-purpose npn unit in a T0-92 style case will do. IC1, an LM334, supplies Ql with a constant current that is independent of temperature. An LM324 quad op amp, IC2, forms a....
To decouple the sensors from the meter amplifier, either a reference junction at ooc or a bucking voltage set at room temperature may be used. The latter method is simpler, but is sensitive to changes in ambient temperature. ..
The temperature sensor provides an input to pin 3 of the NE5037 of 32 mV/°C. This 32 mV is the value of one LSB for the NE5037. The LM334 is a three-terminal temperature sensor and provides a current of 1 p.A for each degree Kelvin. The 32-KO resistor....
This circuit uses the +5 V reference output and the op amp to level shift and amplify the 2.1 mV/°C Tempco output into a voltage signal dependent on the ambient temperature. Different scaling can be obtained by selecting appropriate resistors from the....
A simple op amp and silicon diode are the heart of the temperature-to-voltage converter that will permit you to use an ordinary voltmeter-either analog or digital-to measure temperature. User adjustments make it possible for a reading of either 10 mV or....
This control, with zero-voltage load switching, uses a CA3130 BiMOS op amp and a CA3079 zero-voltage switc..
A thermistor (RI) is compared with a reference (R2) in a Wheatstone-bridge circuit. Comparator Ul"s output goes high..
For the absolute measurement of temperatures, a thermometer is indispensable. However, in many situations, an ..
The reference current is fed from the supply voltage via Rl, to the inverting terminal, and the variable (noninver..
The AD537 uses its two reference outputs—one fixed at 1 V, the other of which varies with temperature (1 mV per °K). At ..
The output goes high when a preset temperature is exceeded. A fixed half-supply reference voltage feeds a reference..
As a sensor in the design of this linear thermometer, the LM34 is used. The output is the difference between..
This thermometer is capable of measuring temperatures from - 30 to +120 °F. A diode-connected 2N3904 transistor form..
This circuit combines a current source and a platinum RTD bridge to form a complete high-accuracy thermometer. Th..
A TDA1024 electronic thermostat senses soil temperature via thermistor R6. The circuit uses zero-crossing switching of the heater. The heater is made of elastic-coated steel wire. PI is used to set the temperature. The heater should have 2 or more....
The telephone-line tester consists of nothing more than a meter (that`s used to measure line voltage in the on- and off-hook state), three resistors (one of which is variable), a pushbutton switch, and a modular telephone connector...
This circuit provides a linear increase of frequency of 10 Hz/°C over 0-100 °C and can thus be used with logic systems, including microprocessors. Temperature probes Ql Vbe changes 2 mV/°C. This transistor is incorporated in a constant current source....
This temperature controller operates as a pulse snatching device, which allows it to run at its own speed and tum on at the zero crossing of the line frequency. Zero crossing tum-on reduces the generation of line noise transients. TMOS Power FET, Ql, is....
The fan employed is one of the new electrostatic type which is very reliable, because it contains no wearing parts. These devices require high-voltage drive. When power is applied, the thermistor, located in the fan"s exhaust stream, is at a high value.....
Both of these converters use CMOS inverters. Figure 105-1A shows a free-running circuit having both the pulse duration and pulse pause dependent on temperature of the diode D8. It can be used where a synchronization between the converter and something else....
The ROMs or PROMs must have the correct code for converting the data from the NE5037 -used as address for the ROMs or PROMs-to the appropriate segment driver codes. The displayed amount could easily be converted to degrees Fahrenheit, °F, by the....
The DVM-to-temperature adapter is built around a single IC, National"s LMlO. That micropower IC contains a stable 0.2 V reference, a reference amplifier and a general-purpose op amp. The circuit is designed for a linear temperature range of 0 to 100°C (32....
This oscillator circuit includes a quartz crystal that has a nominal resonant frequency of 262,144 Hz and is cut in the orientation that gives a large linear coefficient of frequency variation with the temperature. In this type of circuit, the oscillation....
This temperature controller has a range of -50 to +150°C and permits defrosting. R7, VR3, and R8 ..
Using the fact that the VRE of a transistor shifts 59.16 mV per decade of current at 25°C. This cons..
You need to find a reliable full bridge driver to drive your flyback transformer? Well, This is your final stop. There are many flyback drivers schematics out there, but most of them will not last for long. It is common known that famous ZVS invented by....
This circuit provides a regulated dc with less than 100 mV of ripple for microprocessor applications. Necessary operating voltages are taken from the bleeder resistor network connected across the unregulated 28 V supply. The output of the LM710 comparator....
This low-voltage high-current output, sWitching de power supply is running off the 220-Vac input. In this circuit, an ST2 diac relaxation oscillator, Q3, Cl, and the diac, initiates conduction of the output switching transistor Ql, the on-time of which is....
The schematic shows a 50W power supply with a 5-V 10-A output. It is a flyback converter operating in the continuous mode. The circuit features a primary side and secondary side controller will full-protection from fault conditions such as overcurrent. ..
The LTC10432 switched-capacitor building block provides nonoverlapping complementary drive to the Ql to Q4 power MOSFETs. The MOSFETs are arranged so that Cl and C2 are alternately placed in series and then parallel. During the series phase, the + 12 V....
A simple battery-powered switching regulator provides 5 V outfrom a 9-V source with 80% efficiency and 50 mA output capability. When Q1 is on, its collector voltage rises, forcing current through the inductor. The output voltage rises, causing A1"s output....
A shows a COR/CAS circuit for repeater use. CR1 is a silicon diode. 2 may be any relay with a 12-V coil (a long-life..
Switch-mode power supplies offer the benefit of a much greater efficiency than obtainable with a traditional ..
In conventional applications, switching-regulator ICs regulate VQVT by controlling the current through an external inductor. The IC in A, however, driving a diode-capacitor network in place of the inductor, offers comparable performance for small loads. The....
The Max650 switching regulator produces a regulated 5 V from large negative voltages, such as the -48 V found on telephone lines. The resulting power supply operates with several external components, including a transformer, and it delivers 250 mA. The....
The power supply uses two VN4000A 400-V MOSPOWER FETs in a half-bridge power switch configuration. Outputs available are + 5 Vat 20 A and ±15 V (or ±12 V) at 1 A. Since linear three-terminal regulators are used for the low-current outputs, either ±12 V....
An LT1172 generates positive and negative voltages from a 5-V input. The LT1172 is configure..
A shows a typical LTC 1148 surface-mount, application providing 5 V at 2 A from an input voltage of 5.5 V to 13.5 V. The operating efficiency, shown in B, peaks at 97% and exceeds 90% from 10 mA to 2 A with a 10-V input. Ql and Q2 comprise the main switch....
Predictable time delays from as low as 0 milliseconds to over 3 minutes are obtainable without resorting to a large value electrolytic-type timing capacitor..
Circuit (a) lets you delay the leading edge of a positive pulse while leaving the trailing edge almost unaffected. A positive input transition, inverted hy IC2, has no effect on IC1B. However, when the positive transition reaches IC1A, (delayed hy the....
A single monostable multivibrator delays a pulse train by a variable amount; nonetheless, this amount can be no less than the minimum allowed pulse width fw· The exclusive-OR gate, IC1, generates a short pulse following every leading or falling edge of....
You can obtain well over 360° of phase delay by cascading two monostable multivibrators. In a typical configuration, a single monostable multivibrator is used to introduce delay in a pulse train; the multivibrator triggers on each incoming pulse, provided....
The time delay, T, in seconds is: T = 1.1 x Cl x (Rl + R2). The resistances are in megohms and capacitances in microfarads. The sum of R1 and R2 should not be Jess than 1000 0 nor higher than 20 MO. Pressing S1 starts the timing cycle. A low-going pulse,....
Power is applied to the circuit with the initiate switch open. The 25-JtF capacitor charges through the A14, or equivalent, diode and 2.2-KO resistor to full supply voltage. When the initiate switch is closed, the low side of the capacitor is suddenly....
After the first cycle. the relay will normally be energized. When normally closed pushbutton 51 is activated, the SCR turns off, the relay is de-energized, and power is applied to the relaxation oscillator and the load. Mter a time delay varying from....
The alarm/sensor circuit shown is built around two SCRs, a transistor, a 4049 hex inverter, and a few support components, all of which combine to form a closed-loop detection circuit with a delay feature. The delay feature allows you to enter a protected....
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....
Three 555 IC timers are used in this circuit to construct a simple delayed-pulse generator. IC1 acts as a waveform shaper to produce a rectangular waveform. IC2 produces a delaying pulse to trigger 103 on the trailing edge of the delaying pulse. Rl controls....
This circuit uses a Hall-effect sensor, consisting of an IC that resides in a small gap in a flux-collector torrid, to measure de current in the range of 0 to 40 A. You wrap the current-carrying wire through the toroid; the Hall voltage VH is then linearly....
In operation, the TL3019 device will activate, or become low, when a south pole of a magnet comes near the chip face of the device. The example shows five doors. Each door has a magnet embedded in its edge with the south pole facing the outer surface. At....
Hall-effect switches have several advantages over mechanical and optically coupled switches, They"re insensitive to environmental light and dirt, they don"t bind, and they don"t sustain mechanical wear. Their major drawback is that they require three wires....
The TL3103 linear Hall-effect device can be used as a compass. By definition, the north pole of a magnet is the pole that is attracted by the magnetic north pole of the earth. The north pole of a magnet repels the north-seeking pole of a compass. By....
Although not intended for this application, Hall-effect switch can be used as the basis for a rather unusual oscillator. The oscillator can be reconfigured, as shown in Fig. B, to allow the circuit`s oscillating frequency to be controlled via an RC network, ..
The two probes shown are held in the hands and the skin resistance applies bias to the transistor. The 5 k ohm pot is set for zero deflection on the meter. When the ' 'subject'' is embarrassed or lies, sweating on the hands takes place, increasing the bias....
The circuit is built around an LM339 quad comparator, Ul, which forms the basis of a Schmitt trigger, timer circuit, and a window comparator. One comparator within the LM339 (pins 1, 7, 6), plus LDR1, R4, R5, R6 and R8, is used as a Schmitt trigger. The....
This game tests a player"s reaction time. It is activated by closing switch SI, which starts the tone generator and arms the circuit. The touchplate, labeled PLAY in the diagram, consists of two metal strips about l/16th-inch apart. The first player to....
Six LEDs are arranged to produce a display the same as the dots on a dice. When PBI is depressed, the display is blanked and the oscillator (ICl a, b, c) clocks IC2 at about 1MHz. IC2 counts from zero and resets on seven..
The 555 timer produces a rapid series of pulses whenever switch SI is open. These pulses are counted in groups of 16 and converted into binary form by the 7493 and applied to the 74154 (a l-of-16 decoder/demultiplexer) wired so that each of its 16 output....
Circuit uses an astable multivibrator to vary the heads-or-tails condition, and a flip-flop to store the condition given by the multivibrator..
This is a circuit for a game of the shooting gallery variety. IC2a and b form an astable multivibrator clocking ICl which causes LEDs 1-8 to flash in turn LED 5 is the target LED and the object of the game is to depress PBI just as LED 5 comes on. If this is....
The circuit is basically a 555 astable circuit that divides two LEDs, LEDl and LED2. LED2 is switched on when the output of Ul is high, and LEDl is activated when its output is low. When Ul oscillates, LEDl and LED2 switch on alternately as the output....
Using two SCRs, this control circuit is designed to lock out the other SCR when one has been triggered, so only one lamp will light. Indicator lamp Il is controlled by SCRl. The operator simply presses switch Sl. Lamp I2 is similarly controlled by S2....
The basic die circuit is given. A 555 timer, ICl, is connected as an astable multivibrator. This feeds clock pulses to divide-by-six counter IC2 tbe outputs of which are decoded by gates Nl to N6 to drive an array of LEDs in the familiar die pattern. When....
This circuit has a rate multiplier using a 4093 Schmitt trigger as an oscillator, driving a 4017 decade counter. When a pulse p..
This circuit uses a timer to generate pulses at a 5-ms clock rate. The pulses are shifted into the shift register, one at a ..
This circuit is a 10-LED spinning wheel that "clicks" as the wheel passes each point. The rotation starts fast, then gradu..
The electromagnetic ring launcher is comprised of.four subcircuits: a clock circuit (built around U5, a 555 oscillator/timer configured for astable operation), a count-down/display circuit (built around U3), a 74190 synchronous up/down counter with BCD....
Up to eight players each have their own answer button to press, corresponding to the four Red Team and four Green Team LEDs on the master control board. As soon as the first contestant who thinks that he knows the answer presses the button, a loud tone....
The slot machine`s realistic action is provided by seven ICs and three displays, as shown. Two 555 CMOS timer ICs generate pulses. IC1 is used to generate the clock pulses for the entire electronic slot machine. The pulses are coupled from the output (pin....
The circuit, uses a two-transistor direct-coupled oscillator that has a frequency determined by CI, R2, and the (skin) resistance across the touch pads. Since CI and R2 are fixed values, only the skin resistance across the touch pads can vary the sound of....
The persona] message recorder is built around an ISD1016 CMOS voicc messaging system, which does away with the cumbersome and expensive analog-to-digital and digital-to-analog conversion circuits. A functional block diagram of the ISD1016 is shown. The....
This device prevents paper notes and memos from being overlooked. A paper note placed between two fingers made of a conducting material (metal or conductive plastic) breaks the circuit, allowing pair 1 of Ul-a to go high...
The signal starts at a low frequency, rises for about 1.15 seconds to a high frequency, ceases for about 0.35 seconds, then starts rising again from a low frequency, and so on ad infinitum. ..
A large number of intercom stations can be tied together. All units are connected in parallel, and the entire system is buzzed by only one signaling circuit. Each unit is powered individually from 1.5-V cells for redundancy. For greater signal volume, 3-V....
The circuit provides a minimum component intercom. With switch SI in the talk position, the speaker of the master station acts as the microphone with the aid of step-up transformer Tl. A turns ratio of 25 and a device gain of 50 allows a maximum loop gain of....
When activated, the transmitter sends out a 49.890-MHz, AM rf carrier. The.receiver detects, amplifies, and decodes the rf signal, which, in turn, activates a piezo buzzer. The receiver is small enough to carry in a pocket or sit on your workbench. ..
Amplifier A increases the microphone"s output to a usable level. The output signal is fed to op amp B, which inverts the signal180°. A balance-control potentiometer connects across the outputs of amplifiers A and B. 1f an audio tone is fed into the....
The design consists of an amplifier, a double-pole changeover switch and two loudspeakers: one for the master station and..