If you require a simple circuit for audio driven or reactive LEDs then this simple audio controlled LEDs circuit can do the job very efficiently and you can make beautiful sound effect LEDs with it.
The circuit require a small amount of audio signal at the audio input points shown in the diagram, the
audio input can be from the output of the headphone socket of any audio playing device like mp3 player, CD player, computer, radio, walkman etc.
The circuit is using only 15 LEDs and each three LEDs are connected with a single current limiting resistor of 75 Ohms. The number of LEDs can also be increased in the circuit, but make sure to connect them in the same manner as we have connected. The circuit is using a BD140 PNP transistor with this transistor you can connect upto 60 LEDs with the circuit. For further increasing the number of LEDs you can use a TIP32 or MJ2955 transistor. Also note that if you are using higher number of LEDs and operating the circuit with power supply then use a higher ampere power supply for example 2 to 3 amperes.. On driving higher number of LEDs the transistor will become hot therefore it is important to use a suitable heatsink with it. The operating voltage of the circuit is 12V DC.