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January 2011
Reliable 555 timer doesn’t falsely trigger
Test continuity with an LED
Flash an LED from ac-mains power
Transistors drive LEDs to light the path
Use an optocoupler to make a simple low-dropout regulator
Power an LED driver using off-the-shelf components
Oscillator has voltage-controlled duty cycle
Generate noisy sine waves with a sound card
Decode a quadrature encoder in software
February 2011
Compute a histogram in an FPGA with one clock
Control an LM317T with a PWM signal
High-speed buffer comprises discrete transistors
Limit inrush current in high-power applications
Protect MOSFETs in heavy-duty inductive switched-mode circuits
Reduce acoustic noise from capacitors
Function generator has varibale frequency
Power supply accepts wide input-voltage range
Circuit lets you test capacitors
March 2011
Design provides single-port-to-dual-port SDRAM converter
Zener diode protects FPGA inputs
Bicolor LED indicates 10 states
Relay driver switches two relays with one pin
Anticipator circuit speeds signal settling to a final value
Schmitt trigger provides toggle function
Active multiplexing saves inputs
Finely tune the hue of blue-light sources
April 2011
Low-component-count logic probe works with TTL and CMOS logic
Circuit implements photovoltaic-module simulator
Switch circuit controls lights
Isolated PWM suits low frequencies
Increase efficiency in embedded digital-I/O lines
Modulating a reference allows maximum-value search for phase detection
Offline supply drives LEDs
Light an LED without wasting energy
May 2011
Circuit secures bootstrap operation under light load
Build an accurate bipolar voltage reference
Send MIDI signals over long distances
MOSFET provides high power at low loss
Waveform generator minimizes amplitude dependency
Produce current from positive or negative high-voltage supplies
Arrange LEDs as seven-segment displays
Logic gates form high-impedance voltmeter
Measure resistance and temperature with a sound card
June 2011
Potentiometer calibrates photodiode amplifier
Drive 16 LEDs with one I/O line
Circuit measures battery capacity
Programmable driver targets piezoelectric actuators
Circuit boosts voltage to piezoelectric transducers
Protect power-LED strings from overcurrent
Simple flasher operates off ac mains
Use resistor noise to characterize a low-noise amplifier
Build a UWB pulse generator on an FPGA
Generate swept sine/cosine waveforms with two filters
July 2011
Compensate for four-wire sensor errors
LED-current limiter accepts ac or dc
Voltage inverter employs PWM
Form positive pulses from negative pulses
Positive edges trigger parabolic timebase generator 07/28/2011
Measure small currents without adding resistive insertion loss
Power resistor varies in value
Minimize noise in power-supply measurements
August 2011
Driver circuit lights architectural and interior LEDs
Use op amps to make automatic-ORing power selector
Charging time indicates capacitor value
Circuit provides universal ac-input-voltage adapter
Logic probe uses two comparators
DAC fine-tunes reference output
LEDs indicate sound level
September 2011
Polynomial rotation accelerates CRC calculations
Simple circuit measures optocoupler's response time
Circuit provides visual verification of IR pulses
An LED's intrinsic capacitance works in a 650-mV LRC circuit
Eight LEDs make a 100-division voltmeter
Simple circuit controls the rate of voltage change across a capacitor or another load
LED bar-graph display represents two digits
October 2011
Circuit controls inrush current in ac-operated power supplies
Save 3 dB of output power using feedback to set the output impedance
Optically isolated overcurrent detector works from ac mains
Simple circuit helps to protect a vehicle-reverse camera
Use a self-powered op amp to create a low-leakage rectifier
Simple reverse-polarity-protection circuit has no voltage drop
Series-LC-tank VCO breaks tuning-range records
November 2011
Circuit detects rapidly falling signals and rejects noise
Hack into a stopwatch to make a phototimer
Comparator directly controls power-MOSFET gate
AGC circuit uses an analog multiplier
Add extra output to a boost converter
Fabricate a high-resolution sensor-to-USB interface
Converters yield droop-free S/H circuit
December 2011
Inexpensive VFC features good linearity and dynamic range
Mains-driven zero-crossing detector uses only a few high-voltage parts
Build an op amp with three discrete transistors
A diode ladder multiplies voltage under software control
Charger extends lead-acid-battery life
Circuit provides more accurate multiplication
A few added components make a self-contained controller for 100A load
Simple night-light uses a photoresistor to detect dusk
Simple tester checks Christmas-tree lights

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