The audio player was built using an SD memory card and the ATtinyX5 series 8-pin AVR microcontroller. [via]
8-Pin Microcontroller Based SD Audio Player – [Link]
You might find yourself needing a low power H bridge for driving a motor like I once did. The 555 IC can drive a load up to 200mA, source or sink, which might make is usable as a driver, if one can control the output as desired.
555 / 556 H bridge – [Link]
A certain knock at the door may tell you if the person behind it is the one expected or just somebody else. Each knock on the door itself cannot tell you too much, it can be lighter or stronger and that’s all about it, there’s no information on pitch here. But a certain sequence of knocks can be an actual secret code. The secret knock is encoded in the actual timings of the knocks, the time between each knock creating a distinguished pattern.
Secret knock detector with 555 – [Link]
One of the applications of 555 timers is a class D amplifier. In its most simplistic form it can be built with a single 555 and the 200mA current capability is enough to drive a small speaker, making it a good replacement for a low power amplifier. But I wanted more; I wanted to use it to build an amplifier that had enough power to allow listening to music in a small room. Adding a high power stage to a classical 555 class D amplifier was too easy, so I decided to build my own high power 555.
555 class D amplifier - [Link]
dangerousprototypes.com writes: [via]
Here’s a project which unifies art and tech: a LilyPad Cyclocomputer. Mark Fickett designed this bicycle computer which uses a magnet and reed switch as a cyclocomputer wheel sensor. This sensor is read by the Arduino/LilyPad (Atmega328) which processes the data and stores two trip meters and a speed histogram; the trip meters are reported in Morse code via a speaker, and the histogram can be saved to EEPROM and later printed over the serial connection.
Arduino Cyclocomputer – [Link]
Here’s a Leach Amplifier based on 2SC5200 and 2SA1943 output power transistors that can provide up to 700W of power. The mechanical design is relatively simple, the transistors are placed on the two cooling profiles with a height of 66 mm, width 44mm, overall length 260mm. They are turned against each other Thus, from the cooling tunnel. Coolers are attaching the nylon backing which allows the assembly of transistors without washers, and thus better transfer of heat. DPS amplifier is at the top of the tunnel and the transistors are soldered from the bottom of PCB.
700W Leach Amplifier – [Link]