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DIY wristwatch using Atmega328P

Posted on September 27, 2013 by R-B Leave a comment

Zak Kemble from England has shared his digital wristwatch buildon his blog. It is a very neat and clever design using the Atmega328P microcontroller and a 1.3″ OLED for display. The watch is powered by a 150mAh LiPo battery which can be charged via USB. The onboard battery charging circuit uses Microchip’s MCP73832 device. The ATmega328P uses its internal 8MHz oscillator and runs on 2.5V derived from a linear regulator. Time-keeping is done with the DS3231M RTC chip. With 32K of program memory, Zak has implemented many other cool features besides displaying time and date, such as alarm, stopwatch, animation,

AC load dimmer using triac

Posted on September 24, 2013 by R-B Leave a comment

Triacs-based dimmers are based on the principle of controlling the phase of AC voltage applied to the load and are specially designed for resistive loads such as incandescent or halogen lamps. Mike from Electronics-Lab has shared this simple TRIAC AC load dimmer circuit that can handle AC power up to 400VA. The circuit is working by controlling the phase of the 220 VAC voltage allowing the load to be powered for less than 360º of the full sine wave. Powering the load for smaller period than full sine wave delivers less power, so it has a dimming effect on the

DIY mailbox alert system that texts you when letters arrive

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

Here’s a DIY mailbox alert system that will free you from guessing, wondering, or making wasted trips to the mailbox only to find it empty. Yes, this Arduino-based mailbox notifier sends you a text whenever you get mail. The device uses a simple light-dependent resistor (LDR) to detect the light levels inside the mailbox. When somebody opens the mailbox, the light level goes up and Arduino knows it is time to send a text. It can also serve as a security device to avoid your mail being stolen if the mailbox is accessed during non-delivery hours. A push switch button

Proximity sensing for mobile phones SAR requirements

Posted on September 21, 2013 by R-B Leave a comment

Research in to the long term health effects from exposure to radio frequency energy has been ongoing over the past two decades. As a result of this research the FCC and other telecommunications agencies have adopted limits for safe exposure to radio frequency (RF) energy. These limits are referred to as the Specific Absorption Rate (SAR), which is the measure of the amount of radio frequency energy absorbed by the body when using a mobile phone or other wireless device. The FCC and other agencies require that manufacturers of wireless devices comply with these limits for safe exposure. In order

Arduino-controlled plant watering system

Posted on September 19, 2013 by R-B 11 comments

Here is another automatic plant watering system using Arduino. The system continuously senses the moisture condition of soil and activates the water pumping system if the soil condition is too dried. The system also implements a real time clock for timekeeping, LEDs to indicate various soil conditions, and a LCD display to show various parameters including the time and the status of the water pump.

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