This incredibly attractive and easy-to-build device will astound your colleagues and family. LED lamp reacts to a single clap of hands. It has minimal sensitivity to typical ambient sounds such as: speech, music, dog barking and other. Each subsequent clap of hands makes the output IC to the opposite, enabling or disabling the high brightness white LED. After the power is turned on, the system is reset and it enters into standby mode until it “hears” the clapping of hands. Regardless of the status it draws little power from the battery. The printed circuit board was designed to fit in the battery basket.
• Under typical conditions, LED “hears” a clap of hands from a distance of up to 3 meters.
• LED switching on/turned off by a clap of hands.
• Light source: high brightness, white LED.
• Powered from 3 batteries AA size (not included).
• PCB dimension: 35×52mm.
• Electronic Kit – soldering required.
The diagram is shown in Figure 1. The light switch is made up of three blocks: a transistor amplifier, a “T” trigger with a 4017 chip, output buffer with T4 transistor. The microphone signal is amplified by an amplifier with three T1-T3 transistors. R4 resistor and capacitor C2 provide negative feedback. This amplifier amplifies only high-frequency signals from the acoustic band. This makes it less responsive to typical ambient sounds. A strong acoustic signal containing a large amount of high-frequency components causes the transistors T1 and T3 to open. Once receiving clap of hands, positive pulse will occur on the clock input of the 4017 integrated circuit. It causes the change of the state of the counter chip (US1), which through the transistor T4 turns on the white, high brightness LED. Resistor R5 and capacitor C3 reset the counter chip after power up. To supply the LED lamp use 3 R6 (AA) batteries. In the standby state, the LED consumes less than 200uA, while in the active state up to 10mA.
Assembly and test
The assembly diagram is shown in Figure 2 in the user manual. Assembling should start with soldering resistors. Then, the larger components should be soldered. At the end, the US1 chip should be inserted into the socket.
Before soldering the LED, its pins must be bent in “Z”-shape and it should be placed just above the chip. In the next step, the red wire from the battery basket to the "+" and black to the "-" should be soldered (shortening to the required length). To save battery use a battery basket with a switch.
The LED lamp assembled correctly from the tested components operates immediately after the power is turned on. To disperse the emitted LED light, module can be covered with a roller or paper cone, or a disposable white beverage cup. For alkaline batteries, the average lamp life will be approximately 100 hours.
LED1: White LED diode
T1, T2, T4: BC547
US1: 4017 IC with 16-pin IC socket
Battery holder 3×AA with switch