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H-Bridge to drive white LED arrays directly from the AC mains supply

Posted on August 23, 2013 by R-B Leave a comment

The classical H-bridge circuit is widely popular in driving DC motors in robotics applications. This article talks about a novel application of the H-bridge circuit for driving white-LED arrays directly from the AC mains in full-wave current-limited mode to realize an excellent flicker-free, energy-efficient solid-state lamp. The circuit controls and maintains the LED excitation current in both negative and positive half cycles of the excitation voltage to a constant level by way of electronic switches operating alternately during the positive and negative excursion of the excitation voltage.

Low-cost thermostat design for cooking appliances using PIC10F204

Posted on August 20, 2013 by R-B Leave a comment

Countertop cooking appliances, such as electric ranges and skillets, use an adjustable thermostat to vary the heat output. In traditional appliances, a mechanical thermostat was used in series with the heating element to control the current through the element. While this technique is inexpensive, it is less accurate and less reliable over time because the mechanical components wear out. This application note from Microchip describes a low-cost microcontroller-based design which eliminates these drawbacks. The solution uses the PIC10F204 microcontroller, which gathers user inputs from a potentiometer and control current to the heating element via a triac. The application note also

Arduino-controlled prosthetic hand operates on verbal commands

Posted on August 19, 2013 by R-B Leave a comment

Here is a really cool instructable about making a prosthetic hand cum arm that operates on voice commands. The project uses a modified version of the InMoov hand/forearm to construct a five-finger prosthetic hand, which is controlled by an Arduino Uno along with a voice-recognition shield. This hand can perform 15 general hand gestures and actions that are used in daily life, such as pinch, peace, thumbs up, point, etc.

High-voltage seven segment LED display driver with SPI interface

Posted on August 19, 2013 by R-B 44 comments

Seven segment LED displays are known to be resource and power hungry. But because they are visually so charming and readable from a far viewing distance and at a much wider viewing angle as compared to any other electronic displays, they are still hugely popular. The required number of I/O pins to drive the LED segments can be reduced significantly by using an additional dedicated hardware. For example, the MAXIM’s MAX7219 device allows you to interface 8 pieces of seven segment LED modules using only 3 I/O pins of Arduino or any other microcontroller. You can find details on the

Data recovery from a dead SD card using Arduino

Posted on August 19, 2013 by R-B Leave a comment

A Secure Digital (SD) memory card is the most standard memory card for use in mobile electronic devices, such as cell phones, digital cameras, GPS devices, and tablet computers. Communication with an SD card can be done in one of two modes: the SDIO mode and the SPI mode. By default, the SD card operates in the SD mode, which is much faster than the SPI mode and is thus more preferable in the portable devices for achieving high-speed data transfer. If you have a damaged SD card that contains valuable information, this example shows you might have a chance

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