Let’s imagine that you need to add a power switch to something that’s battery-powered but processor-free; perhaps it must also be waterproof and thus membrane-sealed...
To press on or hold off? This does both
Hack into a stopwatch to make a phototimer
The exposure tester in this Design Idea measures the on time of a light source, whether an LED, an incandescent lamp, a halogen lamp, or another source...
Comparator directly controls power-MOSFET gate
It is common practice to power a MOSFET with a comparator and with an unregulated voltage and to power the comparator driving it from a regulated one...
Improved PRTD circuit is product of EDN DI teamwork
Recently I published a simple platinum resistance temperature detector design idea that was largely inspired by a deviously clever earlier DI by Nick Cornford...
Circuit improves on temperature measurement
When current pulses with a stable IHIGH/ILOW ratio modulate a semiconductor junction, the ensuing voltage difference is a linear function of the absolute (Kelvin) temperature...
Quartz oscillator with shock excitation
The circuit seems utterly simple but demonstrates unusual behavior. It produces an almost square wave of odd-integer quartz harmonics, including its main frequency...
DC power wire also carries clock or data
A high-side current-sense amplifier offers a simple method of combining low-speed clocks or other signals with dc power in cables between subsystems...
Simulate input-offset current for current mirrors
Simulating the output-offset current of a current mirror is straightforward. You simply have to apply an input current, measure the output current, and calculate the difference. This output-offset current, however, is not equal to the input-offset current...
The power of practical positive feedback to perfect PRTDs
Frequent contributor Nick Cornford recently published a delightfully clever design idea using a platinum RTD calibrated to output a 1 mV/°C signal that’s perfect for direct readout via a standard DMM…
Electromechanical damping stabilizes analog-meter readings
Before shipping moving-coil meters, manufacturers may short-circuit the meters' terminals with a length of wire, which provides effective electromagnetic damping and results in better immunity to external mechanical vibration and shocks that can occur during transportation...
