Knowledge
Hard disk (HDD) is an important device which works as the computer's data storage after the file is saved to the hard drive. If the hard drive has a large capacity it can save a lot as well. It is also an area for your computer's operating system, so the hard drive is like a filing cabinet of your computer.  Read more about hard disk....
All teachers wish to find the teaching aids for students in order to make them understand in what they are studying or practice in their experiment, but the big problem is those teaching aids have expensive to serve that requirement cause by insufficient of allocated budget. By the other hand, changing idea to find recyclable material and make it as teaching aid tools instead could solve budget problem as well. Read more information ....
Musical robot working by the principle of electromagnetism to launch a mobile rod rap or outlet of various musical instruments by using of hard disk reading arms with permanent magnet. Read more about musical robot ....
Hard disk reading head can work as electrical generator by its moving through magnetic field of permanent magnet. The hard disk head and arms are installed by attach to the front end aligned in a circle on the cycle base with a permanent magnet. Rotating of hard disk head means magnetic field of a permanent magnet can be cut with coil then an electric current flowing in a coil apply to a small light bulb. Read more about generator....

Other contents
Musical fountain, reading head is an internal parts of the unused hard disk that can be refurbished as many kind of toys. Particular, the invention as musical fountain used hard disk reading arms and permanent magnet on both sides of the coil which work as the water valve so-called Solenoid valve. Read more about musical fountain .........