Issue 263: Net-Enabled Controller, MCU-Based Blood Pressure Cuff, MOSFETs 101, & More

Although the June issue is still in production, I can report that it’s packed with projects and tips you’ll find immediately applicable. The projects include an AC tester design, an Internet-enabled controller, a DIY image-processing system, and an MCU-cased blood pressure cuff. Once you’ve had your fill of design projects, you’ll benefit from our articles on essential topics such as concurrency embedded systems, frequency mixers, MOSFET channel resistance, and “diode ORing.”

An Internet-Enabled Controller, by Fergus Dixon
Power-saving smart switches require a real-time clock-based controller. With a request for an Ethernet interface, the level of complexity increases. Once the Ethernet interface was working, connecting to the Internet was simple, but new problems arose.

Final PCB with a surface-mount Microchip Technology ENC28J60 Ethernet chip (Source: F. Dixon, CC263)

AC Tester, Kevin Gorga
The AC Tester provides a modular design approach to building a tool for repair or prototyping line voltage devices. In its simplest form, it provides an isolated variable AC voltage supply. The next step incorporates digital current and voltage meters with an electronic circuit breaker. The ultimate adds an energy meter for Watts, VA, and VAR displays.

The AC Tester powered up and running. The E meter is shown in the plastic case on the top of the tester. The series current limit bulbs are on the top. (Source: K. Gorga, CC263)

Image Processing System Development, by Miguel Sánchez
Some computer vision tasks can be accomplished more easily with the use of a depth camera. This article presents the basics on the usage of Microsoft’s Kinect motion-sensing device on your PC for an interactive art project.

Build an MCU-Based Automatic Blood Pressure Cuff, by Jeff Bachiochi
Personal health products are becoming more and more commonplace. They reinforce regular visits to personal physicians, and can be beneficial when diagnosing health issues. This article shows you how to convert a manual blood pressure cuff into an automatic cuff by adding an air pump, a solenoid release valve, and a pressure sensor to a Microchip Technology PIC-based circuit.

A manual blood pressure cuff adapted into an automatic cuff by adding an air pump, a solenoid release valve, and a pressure sensor to a microcontroller. (Source: J. Bachiochi, CC263)

Concurrency in Embedded Systems, by Bob Japenga
This is the first in an article series about concurrency in embedded systems. This article defines concurrency in embedded systems, discusses some pitfalls, and examines one of them in detail.

Radio Frequency Mixers, by Robert Lacoste
Frequency mixers are essential to radio frequency (RF) designs. They are responsible for translating a signal up or down in frequency. This article covers the basics of RF mixers, their real-life applications, and the importance of frequency range.

MOSFET Channel Resistance: Theory and Practice, by Ed Nisley
This article describes the basics of power MOSFET operation and explores the challenges of using a MOSFET’s drain-to-source resistance as a current-sensing resistor. It includes a review of fundamental enhancement-mode MOSFET equations compared with Spice simulations, and shows measurements from an actual MOSFET.

Diode ORing, by George Novacek
Diode ORing is a commonly used method for power back up. But there is a lot more behind the method than meets the eye. This article describes some solutions for maintaining uninterrupted power.

The June issue will hit newsstands in late May.

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