An electronic circuit is assembled inside a CD case with a headphone jack on the side. The device plays back 40 minutes of low-fi 1-bit electronic music—the lowest possible digital representation of audio. The device is available for $25 and it’s sold as a form of art.
40 Minutes Of Low-Fi 1-Bit Electronic Music: [Link]
This is one of the smallest fan controllers I’ve seen. It does the same job as others, it controls the fan speed according to a temperature sensor. The main utility is that you save power this way, and second its noise reduction, the fan will now run most of the time at lower speeds. The whole circuit its based on 3 parts:
These are really easy to get parts, so you wont have any trouble. As a last word this is a very useful and simple to build project. Good luck building it.
Fan Temperature Controller: [Link]
This is a very small telephone exchange system with two ordinary telephones attached. Full bi-directional facility with an intercom system: when a phone is in off hook condition , the circuit will detect it & send ringing pulse to the other phone. When it will be picked up , the connection will be established between both phones. This will take place vice-versa also. This project sounds great if you need a simple and efficient communication system, like in a tree house, you place on telephone in the tree house and the other one in your house. This is just an example but there are far more applications for this system.
Two way telephone system: [Link]
