By Anthony H. Smith, October 01, 2009
When Electronic Design asked me to write about my Idea for Design, first seen in this year’s August 13 issue, it seemed a simple enough task. We’re all familiar with design. Most of us do it in some form or another almost every day. But, ideas
By Anthony H. Smith, August 13, 2009
A full-wave rectifier that exploits the fact that the output voltage of certain single- supply op amps is effectively “clamped” to ground is described.
By Anthony H. Smith, June 11, 2009
Monitoring the current taken by a mains-powered appliance can be a challenge. Here's an approach centered on Hall-effect sensors and current-sense transformers, which afford the galvanic isolation required for operator safety.
By Anthony H. Smith, August 03, 2006
Many microcontrollers feature a pulse-width-modulated (PWM) output that can be low-pass filtered to produce a variable dc voltage. Without additional circuitry, however, this technique is limited to controlling very low-power loads. The circuit here
By Anthony H. Smith, October 28, 2004
This voltage-booster circuit for driving one or more white LEDs uses a 555 timer as its main element (see the figure). The timer, IC1, functions as a resettable astable multivibrator where R1, R2, and C2 are...
By Anthony H. Smith, March 29, 2004
Implementing a current limit with a ground-referred load often requires a power transistor, a high-side current-sense resistor, and some form of level shifting to get the current-sense signal referred to a convenient potential, usually ground. The...
By Anthony H. Smith, July 07, 2003
The thyristor or silicon-controlled rectifier (SCR) provides a convenient latching mechanism for switching power to a load. However, once the thyristor is triggered into conduction, it supplies no means of controlling the current flow, which is...
By Anthony H. Smith, July 22, 2002
Designed to complement conventional 4- to 20-mA analog signaling, the Highway Addressable Remote Transducer (HART) protocol supports two-way digital communications for process measurement and control devices. The protocol uses frequency-shift keying...