surface so it will blink LEDs when guitar is played, It can be placed on the surface of a loud speaker box to blink LEDs on music etc.
The circuit is very simple to build and using only two transistors and few other discrete components. A peizo electric sensor is used to sense the knock or vibration. The sensitivity of the circuit can be adjusted with the 1M variable resistor. The operating voltage of the circuit is 9V to 12V DC. It can also be operated with lower voltages like 5V or 6V. If you are operating the circuit with lower voltage then use 220 Ohms resistors in the place of 470R for brighter LED light. For best performance fit the circuit in a small enclosure with lithium coin batteries.