Ciarcia’s Circuit Cellar, Vol. 1-3

Many electronics enthusiasts have fond memories of Steve Ciarcia’s first run of Circuit Cellar articles in BYTE magazine. Since Circuit Cellar headquarters still gets inundated with requests for these columns and subsequent Circuit Cellar books (all out of print), Steve has agreed to make these books available online.

Please enjoy these first three volumes. Look for more in future Circuit Cellar News Notes newsletters.

The real purpose behind “Ciarcia’s Circuit Cellar” (1978) is to involve, educate, and motivate the reader… it is to provide a timely and cost effective design which will aid the personal computer enthusiast and enhance his or her system… -Steve Ciarcia

Vol. 1

Vol. 2

Vol. 3

EQ Interactive

Problem

The circuit shown below is the classic op-amp difference amplifier, in which V_OUT = R_Y/R_X(V_P – V_N).

This circuit has several pitfalls for the unwary, however. For example, even assuming an ideal op-amp, what is required to achieve a high common-mode rejection ratio (CMRR)?

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Answer

The CMRR of the circuit is extremely sensitive to how well the resistors are matched; specifically, the R_Y/R_X ratio of the upper half must match R_Y/R_X of the lower half. For example, resistors with 1% tolerance must be used in order to guarantee a CMRR of just 40 dB, and 0.01% resistors are needed to get to 80 dB.

Wheels, Tracks, or Legs: Options Abound at Fire Fighting Home Robot Contest

More than 100 teams from six countries signed on to participate in the 2009 Trinity College Home Robot Fire Fighting Contest. Circuit Cellar magazine is a proud sponsor of this event, which is held at nearby Trinity College in Hartford, Conn.

During the competition, the autonomous computer-controlled robot must respond to a fire alarm, discover the blaze, and extinguish it in the shortest possible time. To accomplish that task, the robot must navigate a maze that resembles a typical house, locate the fire (a burning candle), extinguish it, and optionally return to the starting point.

As seen in the following video, competitors used various methods for robot propulsion, sensing, and fire suppression.

Circuit Cellar would like to thank Parallax Inc. for contributing additional prizes for the event. Prizes, including the Scribbler Robot, Boe-Bot Robot Kit, and the BASIC Stamp Activity Kit, pictured here, went to winners of the Robot Olympiad exam. The exam consists of about ten questions, each presenting a real problem that might arise during robot design projects. Each question requires a solution based on theoretical background and practical experience.

Circuit Cellar congratulates all of the winners and participants in this event.

For more information about this annual event, visit http://www.trincoll.edu/events/robot/

For more information about Parallax, visit www.parallax.com.

STMicroelectronics Announces Multi-City North America Seminars for 8-bit Microcontrollers and Embedded Control Solutions

STMicroelectronics, a world leader in analog ICs and microcontrollers, announced that registration is now open for two of its most popular North America seminar series: motor- and motion-control solutions and STM8S, ST’s new 8-bit microcontroller. Developed by STMicroelectronics and promoted in partnership with its distributors*, the series of free seminars provide hands-on training that delivers practical design guidance and showcases ST’s leading-edge technologies. -More-

Microchip MASTERs Conference

Join embedded design engineers from around the globe July 27 - Aug. 1 in Phoenix, AZ at the 13th Annual Microchip MASTERs Conference! With over 80 different technical classes offered for all experience levels, you can be sure to find a curriculum to help you become an expert in practically any embedded control application! Enjoy fun activities too – with a variety of evening events and networking opportunities available each night for you and your family. Save $155 when you register by 5/8/09.

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