This project was intended to put a smile on a bloggers face on Christmas, the yuletide season is over but we wouldn’t mind putting smiles on every bloggers face each time a bell rings.

The hit counter concept is fairly simple, when someone hits your blog a bell will ring. Simple huh? The implementation was not as simple as it sounds though, to tap into the blog of interest multiples programming languages was used – phyton and PHP – PHP is the base of most blogs it runs in apache, while phyton is a very powerful language when it comes to web-embedded interfacing. When the blog gets hit by a viewer it sends a signal, through phyton and PHP, to an Arduino board which in turn will send pulses that will trigger a servo motor, the bell attached to the servo’s paddle will then generate the ding dong of a blogger’s lifetime!

Remember the laser based alarm system that you see in spy movies? The one that sets the alarm when the laser gets cut by any object? Guess what, – you can have one at home! And what’s more? You can make one using an arduino!

This project was featured in instructibles.com, it’s a fairly simple approach in building a laser based security system – and don’t get me wrong the laser is visible unlike the ones in mission impossible where they use infrared. A laser diode / pointer is biased using a resistor and a battery and a switch is place on series to have a way of turning it on and off. The other end of the system is made up of a photo resistor attached to an arduino. The laser is positioned so that the light hits the photo resistor and when some one cuts the light the change in the resistance in the photo resistor will be detected by the arduino and in turn it will fire the alarm – the good old buzzer! And the best part of this project? It comes in Altoids!

In fact GSM shield is called SM5100B Cellular Shield. So this project is simple – programming Arduino to send text messages, dial the number. Tutorial goes step by step how to connect Cellular shield to Arduino mega and communicate to it by using newsoftserial Arduino library. Whole process steps are monitored in terminal window, so it is easy to follow whats going on during each step of program run.

In the end you will see that using cellular shield is really easy – you can send text messages or make a call by sending couple AT commands. It seems that there will be more info on that, so keep an eye on it.

Digital Tachometer or RPM (Revolutions Per Minute) counter is a tool telling the speed of some object rotation. In real world tachometers often can be fount in most cars panels. RPM indicates rotation of engines crankshaft. It usually gives some information to drivers on throttle and gear usage. So PyroElectro have built a digital RPM counter that can be used for most setups like fan motors or other spinning parts. It is based on optical detector where infrared diode is directed to receiver and moving object interrupts signal at some rate. Having this information RPM can be calculated by microcontroller.

Particularly this project was aimed for measuring RPM of PC fans. So The RPM scale is limited to 1200 – 3200 RPM. Digital RPM value is displayed on standard LCD.

Be sure to check out another great PC fan speed tester.