Click para ampliarThree Way Touch Lamp
A three-way switch to control a lamp (off-dim-bright, etc.) uses an NE555 timer to generate a one-second pulse, triggered by ambient ac fields that are picked up by the human body. C1 and D1 form an input network. U2 is a decode counter/divider and drives one of 10 outputs (three are used). The logic outputs drive various resistors in series with the LED in the optocoupler. The optocoupler controls a triac that is in series with a load (lamp, etc.).
By reconfiguring the outputs of U2, more than three brightness levels can be obtained, up to 10. An 1N914 and resistor will be required for each output.
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By reconfiguring the outputs of U2, more than three brightness levels can be obtained, up to 10. An 1N914 and resistor will be required for each output.
Click para ampliarThree Power Level Triac Controller
Three power levels are supplied by the two logic inputs of this enhanced circuit. R5, D4, D5, and
C2 form a power supply for the logic IC. They can be omitted if another source of low voltage is available.
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C2 form a power supply for the logic IC. They can be omitted if another source of low voltage is available.
Click para ampliarSensitive Triac Controller
The single transistor connected between the capacitor and the common side of the ac line allows a logic-level signal to control this triac power circuit. Resistor R2 prevents false triggering of the triac by the trickle current through the diac.
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Click para ampliarLight Modulator
The light seem to dance in time with the music. Line-voltage lamps of about 40 to 100 W do nicely. The current for the lamp is from an SCR. When low-level audio is present across T1, SCR1 is not triggered into conduction. A louder signal, however, triggers the SCR so that the lamp lights and follows the sounds.
Since SCR1 is operated by an alternating current, the rectifier moves out of the avalanche condition when the gate current is low. Potentiometer R3 lets you adjust the power reaching transformer T1, so that with normal operating volume, SCR1 triggers again and again, except during quiet passages.
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Since SCR1 is operated by an alternating current, the rectifier moves out of the avalanche condition when the gate current is low. Potentiometer R3 lets you adjust the power reaching transformer T1, so that with normal operating volume, SCR1 triggers again and again, except during quiet passages.
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LED Brightness Control
The brightness of LED display is varied by using a photocell in place of one timing resistor in a 555 timer, and bypassing the other timing resistor to boost the timer's maximum duty cycle. The result is a brighter display in sunlight and a fainter one in the dark.
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Click para ampliarDC Lamp Dimmer
A low power, low cost dc lamp dimmer for a two-wire portable "flashlight" can be realized with little or no heatsinking. In addition, a single potentiometer, R3 adjusts lamp brightness. Battery power is stored in C1 for U1, which is a free-running multivibrator whose frequency is determined by R1, R2, R3, R4, and C2. U1 drives the gate of Q1, turning it and the lamp ON and OFF at a rate proportional to the multivibrator duty cycle.
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Click para ampliarAutomatic Light Controller For Carport
A 555 timer IC, operating in the one-shot mode, is triggered by light striking photoresistors. These normally have a resistance of several megohms but, in the presence of light, that resistance drops to several hundred ohms, permitting current from the six-volt source to flow in the circuit. The R-C combination shown gives an on-time of about two minutes. Photoresistors PC3 and PC4 are mounted at headlight-height. When headlights illuminate the photoresistor, the timer starts. That actuates a relay, RY1, and the lights are turned on. The lights are automatically turned off when the timer's two minutes are up.
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Click para ampliar120 AC Shimmering Light
You can turn any ordinary household bulb into one that shimmers or blinks. This circuit works on any incandescent light up to 200 W, and runs on standard 120 Vac. The circuit uses an SCR to cause an ordinary lamp to shimmer. Note that one side of the lamp is connected directly to 120 Vac, and the other side of the lamp goes to the cathode of the SCR. As ac voltage is brought into the circuit through the line cord, it is full-wave rectified by diodes D1 and D2. That changes the ac to dc, and a portion of that dc voltage is applied to capacitor C1 through R2. Diode D3 blocks the (+) dc voltage so that only the voltage from the path of R1 and D3 is clear.
That forms an oscillator, which has a frequency determined by the setting of potentiometer P1 (because the other components have fixed values). Remember to use EXTREME CAUTION when using a device that connects to the ac line. NEVER use it outside or near water and always mount the entire kit inside a wooden or plastic (insulated) box to prevent any contact with the ac voltage.
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That forms an oscillator, which has a frequency determined by the setting of potentiometer P1 (because the other components have fixed values). Remember to use EXTREME CAUTION when using a device that connects to the ac line. NEVER use it outside or near water and always mount the entire kit inside a wooden or plastic (insulated) box to prevent any contact with the ac voltage.
Click para ampliarTriple Op Amp Instrumentation Amplifier
VOUT = VIN (1+ (R1+R2)/R3) (R6/R4)
GAIN = 100
GAIN LIN = 0.002%
SLEW RATE = 2.5V/sec
PSRR = 112dB
IF (R6/R4 = R7/R5) THEN CMRR = 120 dB
ADJUST R7 FOR MAXIMUM CMRR
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GAIN = 100
GAIN LIN = 0.002%
SLEW RATE = 2.5V/sec
PSRR = 112dB
IF (R6/R4 = R7/R5) THEN CMRR = 120 dB
ADJUST R7 FOR MAXIMUM CMRR
Click para ampliarLMC6062 Instrumentation Amplifier
Useful for +5-V single-supply applications, this op amp circuit features low drain (around 1mA), high input resistance (10 e14 ), and low bias current (10 e-14 A).
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Click para ampliarLM6218 High Speed Instrumentation Amplifier
This amplifier features 400-usec settling time (to 0.01%), 140-V/msec slow rate, and 17-Mhz gain-bandwidth product. The supply voltage can be 5 to 20 V.
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Click para ampliarLevel Shifting Isolation Amplifier
The 2N4341 JFET is used as a level shifter between two op amps operated at different power supply voltages. The JFET is ideally suited for this type of application because Id = Is.
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High Gain Differential Instrumentation Amplifier
This circuit includes input guarding, cable bootstrapping, and bias current compensation. Differential bandwidth is reduced by C1 which also makes common-mode rejection less dependent on matching of input amplifiers.
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Click para ampliarExtended Common Mode Instrument Amplifier
These circuits allow a larger common-mode range than most instrument amplifier inputs can allow.
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Click para ampliarBattery Powered Buffer Amplifier for Standard Cell
This circuit has negligible loading and disconnects the cell for low supply voltage or overload on output. The indicator diode extinguishes as disconnect circuitry is activated.
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Click para ampliarWireless IR Headphone Transmitter
The transmitter for the wireless headphones is built around a CD4046 CMOS phase-locked loop, coupled with a driver transistor, and a pair of infrared LEDs. Although the CD4046 is comprised of two phase comparators, a voltage-controlled oscillator (or VCO), a source follower, and a zener reference, only its VCO is used in this application.
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Click para ampliarWireless IR Headphone Receiver
IR detector diode D1 intercepts the IR signal at around 40 kHz and feeds it from U1, a high-gain preamp, to PLL, U2, a 4046 configured to serve as an FM detector. U3 is an audio amplifier that feeds a pair of headphones or a speaker.
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IR Pulse to Audio Converter
If your ear is good, you can use this IR-pulse-to-audio converter to troubleshoot infrared remote-controls. It is also a good project for detecting infrared-light sources. A photo cell module detects IR radiation and drives audio IC U1. This circuit is useful for troubleshooting IR remote
controls.
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controls.
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IR Remote Extender
This circuit can be used to operate a VCR or CD player from another room. It's really an infrared signal repeater. The signal from the remote is received and then retransmitted over wires to an infrared LED. The beam from the LED is then picked up by the receiving window on the VCR or CD player.
The visible light LED (LED1) in series with the IR unit (LED2) is used to indicate that the transmitted signal has been detected. The 100-kW trimmer potentiometer (R1) adjusts the repeater's sensitivity. The resistor that is usually found in series with the LEDs is omitted, because the voltage reading is about 1.0 Vdc as a result of the voltage drop across the lines.
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The visible light LED (LED1) in series with the IR unit (LED2) is used to indicate that the transmitted signal has been detected. The 100-kW trimmer potentiometer (R1) adjusts the repeater's sensitivity. The resistor that is usually found in series with the LEDs is omitted, because the voltage reading is about 1.0 Vdc as a result of the voltage drop across the lines.
Click para ampliarIR Reflection Proximity Switch
IR radiation from LED2 (modulated by a 1-kHz wave) is keyed by U1 , and Q1 is radiated. Reflected IR energy is picked up by Q3, and the audio signal from Q3 is amplified by Q2 and sent to the decoder. The LED1 lights to indicate presence of reflected IR. LED1 can be the input of an isolator so that a triac or SCR can be controlled.
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Click para ampliarIR Receiver
Q3 is an IR phototransistor that responds to a modulated IR beam. Q1 amplifies the ac component of the IR beam. Q2 drives a meter as a relative indication of the strength of the light beam. A strong beam gives a lower meter reading. U1 is a tone decoder that produces a low output on pin 1 during reception for an IR beam that is modulated with the correct tone frequency, determined by R6.
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Click para ampliarInvisible Infrared Pulsed Laser Rifle
The device generates an adjustable frequency of low to medium powered IR pulses of invisible energy and must be treated with care. The portable battery pack is stepped up to 200 to 300 volts by the inverter circuit consisting of Q1, Q2, and T1. Q1 conducts until saturated, at which time, the base no longer can sustain it in an "on" state and Q1 turns "off," causing the magnetic field in its collector winding to collapse thus producing a voltage or proper phase in the base drive winding that turns on Q2 until saturated, repeating the above sequence of events in an "on/off" action. The diodes connected at the bases provide a return path for the base drive current. The stepped up squarewave voltage on the secondary of T1 is rectified and integrated on C2.
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Click para ampliarInfrared Wireless Speaker System
Although the IR region is free from radio interference, it is subject to interference from incandescent lamps, fluorescent lamps, stray reflections, and other sources. A simple way to overcome that problem is to create a carrier by chopping the IR radiation at a rate of 100 kHz. The audio then modulates the carrier by modulating the chopping rate. A receiver then detects the IR beam as a 100-kHz FM signal. The only disadvantage is that instead of a simple audio amplifier, a high-gain FM receiver is necessary. However, with the ICs that are now available, an FM receiver is easy to build, and contains little more circuitry than a high-gain audio amplifier.
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Infrared Remote Controller
The transmitter is built around two CMOS 555 timer ICs (TLC 555s). The transmitter generates a modulated 35-kHz IR signal. The 35-kHz carrier frequency is generated by IC2, and the 1 500-Hz modulating signal is generated by IC1. The output of IC2 drives LED1 through resistor R5; that LED provides visual indication that the transmitter is working. In addition, IC2 drives transistor Q1, which drives the two infrared LEDs (LED 2 and LED 3).
To provide the high current needed to drive the two IR LEDs, capacitor C6 is precharged, the charge it contains is dumped when S1 is pressed. When S1 is not pressed, the power to the ICs is cut off. However, C6 is kept charged via R8. Then, when S1 is pressed, the current stored in C6 can be used to drive the LEDs for as much as 1/2 second. That's plenty of time for the receiver to pick up a signal.
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To provide the high current needed to drive the two IR LEDs, capacitor C6 is precharged, the charge it contains is dumped when S1 is pressed. When S1 is not pressed, the power to the ICs is cut off. However, C6 is kept charged via R8. Then, when S1 is pressed, the current stored in C6 can be used to drive the LEDs for as much as 1/2 second. That's plenty of time for the receiver to pick up a signal.
Click para ampliarInfrared Remote Control Tester
Using a battery, a phototransistor and a visible-light LED, this simple circuit is a go/no go tester for IR remote control devices. The illumination of the LED indicates that Q1 is being modulated by IR energy.
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Click para ampliarFrequency/Voltage Converter
Frequency to Voltage Converter
In these applications, a pulse input at Fin is differentiated by a C-R network and the negative-going edge at pin 6 causes the input comparator to trigger the timer circuit. Just as with a V-to-F converter, the average current flowing out of pin 1 is Iaverage = i x (1.1 R1C1) x f. In this simple circuit, this current is filtered in the network RL = 100 k ohm and 1mF. The ripple will be less than 10 mV peak, but the response will be slow, with a 0.1 second time constant, and settling of 0.7 second to 0.1%.
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Click para ampliarLow Frequency Divider
The ratio of capacitors C1 and C2 determines division. With a positive pulse applied to the base of Q1, assume that C1 = C2 and that C1 and C2 are discharged. When Q1 turns off, both C1 and C2 charge to 10 volts each through R3. On the next pulse to the base of Q1, C1 is again discharged but C2 remains charged to 10 volts. As Q1 turns off this time, C1 and C2 again charge. This time C2 charges to the peak point firing voltage of the PUT causing it to fire. This discharges capacitor C2 and allows capacitor C1 to charge to the line voltage. As soon as C2 discharges and C1 charges, the PUT turns off. The next cycle begins with another positive pulse on the base of Q1 which again discharges C1. The input and output frequency can be approximated by the equation
For a 10 kHz input frequency with an amplitude of 3 volts, the table shows the values for C1 and C2 needed to divide by 2 to 11.
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For a 10 kHz input frequency with an amplitude of 3 volts, the table shows the values for C1 and C2 needed to divide by 2 to 11.
Click para ampliarFrequency Doubler Works to 1Mhz
Frequency Doubler
The output contains the sum component, which is twice the frequency of the input, since both input signals are the same frequency.
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Click para ampliarFrequency Divider
If the input frequency is known, the timer can easily be used as a frequency divider by adjusting the length of the timing cycle. Figure shows the waveforms of the timer when used as a divide-by-three circuit. This application makes use of the fact that this circuit cannot be retriggered during the timing cycle.
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Click para ampliarDivide by -1 1/2 Circuit
An input signal drives both SN7474 D-type flip-flops, which are positive edge-triggered devices. A low-to-high input signal transition triggers the A flip-flop, while a high-to-low input signal transition triggers the B flip-flop via the SN7404 inverter. Either flip-flop in the high state will cause the output to decrease via the SN7402 NOR gate. This in turn disables the opposite flip-flop from going to the high state. The flip-flop in the high state remains there for one clock period, then it is clocked low. With both flip-flops low, the output increases, enabling the opposite flip-flop to be clocked high one-half clock cycle later. This alternate enabling and disabling action of the flip-flops results in a divide-by- 1 1/2 function. That is, three clock pulses in, produce two evenly spaced clock pulses out. The circuit has no lock-up states and no inherent glitches. Replacing the NOR gate with an SN7400 NAND gate inverts the A, B, and output
signals. By adding simple binary or BCD counters, counting chains, such as divide-by-3, -6, -12, -24, -15, -30, etc., can be generated using the divide-by-1 1/2 circuit as a basis.
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signals. By adding simple binary or BCD counters, counting chains, such as divide-by-3, -6, -12, -24, -15, -30, etc., can be generated using the divide-by-1 1/2 circuit as a basis.
Click para ampliarBroadband Frequency Doubler
This circuit will double low-level signals with low distortion. The value of C should be chosen for low reactance at the operating frequency. Signal level at the carrier input must be less than 25 mV peak to maintain operation in the linear region of the switching differential amplifier. Levels to 50 mV peak may be used with some distortion of the output waveform.. If a larger input signal is available, a resistive divider may be used at the carrier input with full signal applied to the signal input.
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Click para ampliarWideband Two Pole High Pass Filter
The circuit provides a 10MHz cutoff frequency. Resistor R3 ensures that the input capacitance of the amplifier does not interact with the filter response at the frequency of interest. An equivalent low pass filter is similarly obtained by capacitance and resistance transformation.
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Click para ampliarVariable Q Filter For 400Hz
A bootstrapped twin T notch filter in this circuit can yield an effective Q of up to 10. Rs adjusts the feedback, hence the Q. Values of C1 and C2 can be changed to alter the frequency. RF is a fine tune null control.
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Click para ampliarVariable Bandwidth Bandpass Active Filter
This circuit has adjustable bandwidth with values for a center frequency of about 800 Hz. The 10 K pot adjusts bandwidth from approximately +-350 Hz to +-140 Hz at 3 dB down points.
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Click para ampliarVariable Bandpass Audio Filter
This circuit is a variable audio bandpass filter that has a low cutoff variable from about 25 Hz to 700 Hz and a high cutoff variable from 2.5 kHz to over 20 kHz. Rolloff is 12dB/octave on both high and low ends. R2-a-b and R6-a-b are ganged potentiometers for setting lower and upper cutoff frequencies, respectively.
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Click para ampliarTunable Audio Filter
This circuit uses a Wien Bridge and variable negative feedback. R7 controls the gain and R8A and R8B controls the tuned frequency.
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Simple High Pass Active Filter For 1kHz
This simple 1 kHz filter uses a voltage follower and an RC section for a filter element. For other frequencies f3 dB - 1/6.28 R1C1. The response drops 6 dB/octave below f3dB.
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