Every spinning object can be described with RPM parameter which means revolutions per minute. And there are many ways of measuring it but basically all methods are classified in two groups – direct contact and contact-less. More popular are contact-less methods of capturing spin period. Most popular are magnetic, optical, capacitive. Each of them are used depending on surrounding environment and materials. Pyroelectro suggests to enter this world using optical method of measuring RPM. He uses an IR LED pair (transmitter and receiver) to capture revolution data.

Setup is based on Arduino UNO which takes care of sending signals to IR diode and reading from receiver. Also it displays data on 16×2 LCD. Reading data is simple – spinning fan blades interrupt IR beam that are captured by Arduino. Then algorithm calculates RPM knowing time measured for one rotation. Method can be used to measure fan speed used in your project or other devices that spin and can interrupt optical beam.

Programing AVR fuses is something you should understand well before hitting button. Lots of starters burned out by trying and failing. So there is a good advice – read, understand and follow documentation. But we all agree that official documentations and datasheets are quite boring to read. This is why it is good to look around maybe there are some great tutorials on this subject.

Embedder’s life have posted a short tutorial about AVR Fuses. It goes through understanding how fuses work, what problems you may face by setting one or another fuse. And finally real examples on how to program fuses using avrdude command line tool.

Digital clocks may obtain different shapes and ways of displaying time. But what is a purpose of building purely digital clock? One of them probably for standing out in the crowd. Not everyone can tell the time by looking ad digital binary values and this makes you look geeky. Another reason is simplicity. Microcontrollers operate with binary values so displaying them is as easy as connecting LEDs to pins. Hawing this in mind Floating Wombat build really simple looking digital clock that uses only four RGB LEDs.

He wanted to make really simple front-face and so ended up with single pushbutton and four LED holes. Obviously he used different colors to tell hours, minutes and seconds. The clock runs on PIC24F16KA102 microcontroller that has internal RTC. 3 AA batteries ensure there is enough voltage for MCU and LEDs. Unique design of box enclosure definitely makes you think what it does… No surprise it is called Obfuscating Chronoscope.

Word clock is an interesting and unique way of displaying time. Instead of showing digits it highlights current time using words. All you have to do is to read words down in order to tell time. Ishan karve designed a word clock using 16×8 LED panel covered with letter mask. He used couple of MAX7219 LED display drivers – each capable to control 64LEDs. And split display panel in to 4×4 modules for easier development and eassembly.

The other part includes control and time keeping. Atmega168 takes care of reading time values from DS1307 RTC and also sends time update signals to LED panel. Since MAX7219 are controlled using SPI interface it doesn’t take much of load. Clock project is still in development so keep an eye on updates.