EDN's Design Ideas

Compact, four-quadrant lock-in amplifier generates two analog outputs

Generate a pair of quadrature-phase digital signals.

Eight-function remote uses one button, no microcode

Simplify the operation of a remote control.

Doorbell transformer acts as simple water-leak detector

Doorbell transformer acts as a power supply.

Inverted regulator increases choice and reduces complexity

A simple approach for any high side overcurrent-protection circuit references the entire circuit to the high-side rail.

Debug a microcontroller-to-FPGA interface from the FPGA side

Monitor activity through a JTAG download cable.

Precision tilt/fall detector consumes less than 1.5 mW

Detect X-axis position and indicate it with an LED.

Reset an SOC only when power is ready

Use a comparator, an AND gate, and a capacitor to properly reset an SOC.

Circuit provides simpler power-supply-sequence testing

New circuit improves on an earlier power-sequence-testing idea.

Inexpensive power switch includes submicrosecond circuit breaker

Control power to a load and protect the power source.

Create a DAC from a microcontroller's ADC

Use a microcontroller's ADC in the feedback loop.

Inspect solar cells without a microscope

Use a short-wave infrared camera to capture the image of an entire wafer.

Solar-powered sensor controls traffic

A traffic-sensor post measures vehicle location and speed at an intersection, providing an accurate, effective, inexpensive approach to monitoring traffic flow

Self-oscillating H bridge lights white LED from one cell

Circuit operates on batteries as low as 0.6V.

Low-cost LCD-bias generator uses main microcontroller as control IC

Control a buck-boost switch-mode regulator with the same microcontroller that sends data to an LCD.

Negative-to-negative switch-mode converter offers high current and high efficiency

Don't let variations in input voltage affect the output voltage.

ADC for programmable logic uses one capacitor

Use a capacitor's charging and discharging time to sense a user input.

Use two phases to cut current and improve EMI

A two-phase SEPIC has lower output-capacitor current, which also improves reliability.

Fader switch uses inexpensive controller

Control the brightness of an LED or incandescent lamp.

Astable multivibrator gets hysteresis from positive-feedback stage

Add hysteresis through positive feedback.

Class B amplifier has automatic bias

Biased transistors minimize distortion.

Cable tester uses LEDs to find faults

Test as many as 16 wires with LEDs as continuity indicators.

Dual-coil relay driver uses only two MOSFETs

Differentially drive relays to minimize power consumption.

Unused port adds a PWM/analog channel to a microcontroller

Take advantage of unused pins to generate a PWM signal and then filter it into analog.

Capacitance meter uses PLL for high accuracy

An improvement on an old design lets you measure capacitors from 10 pF to 1 µF.

Resistor compensates for instrumentation-amp gain drift

Temperature makes instrumentation amp's gain drift; a resistor corrects it.