Design Ideas: Circuit schematics, applications, software, videos contributed by electronic engineers from EDN

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Create a swept-sine function in LabView with just one virtual instrument

Sean McPeak, University of California—San Diego; Edited by Martin Rowe and Fran Granville --EDN, 6/25/2009

Charlieplexing at high duty cycle

Luke Sangalli, Digital Designs, Melbourne, Australia; Edited by Martin Rowe and Fran Granville --EDN, 6/25/2009

Serial port tests digital circuits

Yury Magda, Cherkassy, Ukraine; Edited by Martin Rowe and Fran Granville --EDN, 6/25/2009

DAC calibrates 4- to 20-mA output current

Ronald Moradkhan and Steven Lau, Maxim Integrated Products, Sunnyvale, CA; Edited by Martin Rowe and Fran Granville --EDN, 6/25/2009
When your design requires self-calibration, this circuit will perform the task.

Alarm tells you to close the refrigerator door

Boris Khaykin, TRW Automotive, Livonia, MI; Edited by Martin Rowe and Fran Granville --EDN, 6/25/2009
A simple gadget that you place inside the refrigerator alerts you by beeping if the door stays open for 20 seconds or longer.

Fast 10-line-to-one-line data selector/multiplexer comprises only two ICs

Marián Štofka, Slovak University of Technology, Bratislava, Slovakia; Edited by Martin Rowe and Fran Granville --EDN, 6/11/2009

Implement a simple digital-serial NRZ data-recovery algorithm in an FPGA

Jef Thoné and Bob Puers, ESAT-MICAS, Katholieke Universiteit Leuven, Leuven, Belgium; Edited by Martin Rowe and Fran Granville --EDN, 6/11/2009
A shift register and some logic lets you recover embedded clocks from data streams.

LED strobe has independent delay and duration

Michael C Page, Chelmsford, MA; Edited by Martin Rowe and Fran Granville --EDN, 6/11/2009
High-brightness LEDs, with independent delay and duration, find use in a visual-inspection application.

Cancel sensor-wiring error with bias-current modulation

W Stephen Woodward, Chapel Hill, NC; Edited by Martin Rowe and Fran Granville --EDN, 6/11/2009
This circuit cancels the wiring-resistance error inherent in diode temperature sensors and requires only two conductors in the sensor cable.

Simple FSK modulator enables data transmission over low-speed link

Israel Schleicher, Prescott Valley, AZ; Edited by Martin Rowe and Fran Granville --EDN, 6/11/2009
Send digital data over a low-speed link.

Current-sense monitor and MOSFET boost output current

Gyula Diószegi and János Nagy, Divelex Ltd, Budapest, Hungary; Edited by Martin Rowe and Fran Granville --EDN, 5/28/2009
You can bypass BDC current-settings resistors and use a MOSFET to increase current.

Multiplexed, programmable-gain, track-and-hold amplifier has instrumentation inputs

W Stephen Woodward, Chapel Hill, NC; Edited by Martin Rowe and Fran Granville --EDN, 5/28/2009
This ADC front end implements the standard ensemble of functions.

Simple circuit smoothly drives stepper motors

Uwe Schüler, Institute of Physiology, Tübingen, Germany; Edited by Martin Rowe and Fran Granville --EDN, 5/28/2009

Excel spreadsheet yields RLC best-fit calculator

Alexander Bell, PhD, Infosoft International Inc, New York, NY; Edited by Martin Rowe and Fran Granville --EDN, 5/28/2009
Excel lets you automate engineering functions to find best-fit values of resistors, inductors, and capacitors.

Automatically turn secondary lamp on or off

Vladimir Oleynik, Moscow, Russia; Edited by Martin Rowe and Fran Granville --EDN, 5/28/2009
A transformer and a relay are all you need to automatically turn a spare lamp on or off.

CMOS-NAND gates control sump pump

V Gopalakrishnan, Indira Gandhi Center for Atomic Research, Kalpakkam, India; Edited by Martin Rowe and Fran Granville --EDN, 5/14/2009
A similar circuit lets you control both the sump pump and the water level.

Use an LED to sense and emit light

Rafael Camarota, Altera Corp, San Jose, CA; Edited by Martin Rowe and Fran Granville --EDN, 5/14/2009
LEDs in portable devices often show power status, battery status, or Bluetooth-connection activity. LEDs can be major factors in determining battery life because their intensity is directly proportional to power drain.

Two instrumentation amps make accurate voltage-to-current source

Frank Ciarlone, Analog Devices, Wilmington, MA; Edited by Martin Rowe and Fran Granville --EDN, 5/14/2009
Many designs require precise voltage-controlled current sources, especially in the presence of variable loads. Common approaches, which use a few op amps and a handful of passive components, have inherent errors due to nonideal component characteristics, such as finite open-loop gain, common-mode rejection, bias current, and offset voltage.

Simple circuit indicates health of lithium-ion batteries

Fritz Weld, Friedberg, Germany; Edited by Martin Rowe and Fran Granville --EDN, 5/14/2009
A simple inexpensive circuit quickly indicates a battery pack's health.

Simple method uses PSpice for Thevenin-equivalent circuits

David Karpaty, Analog Devices Inc, Wilmington, MA; Edited by Martin Rowe and Fran Granville --EDN, 4/23/2009
A simple method lets you obtain the Thevenin voltage and resistance and the Norton equivalence with the aid of simulation.

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