Sound Light Robot


In this Instructable you will be making a sound light device. This device turns on the bright LEDs or light bulbs with music. The music input comes from line out or speak output of a HiFi, computer or mobile phone.

You can see the circuit working in the video.


You will need:

- matrix board,

- heat sink,

- NPN power transistor,

- a few NPN BJT general purpose transistors,

- a two PNP BJT general purpose transistors,

- solder,

- soldering iron,

- encasement (you can use a paper cup),

- electric drill (optional),

- heat transfer paste,

- tape,

- 10 ohm power resistor,

- 270 ohm resistor,

- 4.7 kohm resistor,

- 2 Megohm variable resistor,

- two 1 kohm resistors,

- two 10 kohm resistors,

- 100 kohm resistor,

- 470 nF and 100 nF capacitors,

- nut and bolt for the heat sink,

- a few bright LEDs or two 1.5 V light bulbs,

- scissors or screw driver,

- one general purpose diode.

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Step 1: Attach the Heat Sink

Drill two holes in the matrix board and attach the heat sink as shown in the photo.

Step 2: Attach the Power Transistor

Attach the PNP power transistor with bolt and heat transfer paste.

Step 3: Build the Circuit

The Rc2 resistor was chosen as 10 kohm instead of 1 kohm to increase the charging time constant. The time constant is a multiplication of capacitor (C2) and resistor (Rb2) value. An alternative would be to use a higher C2 capacitor value but this would mean using a electrolytic capacitor which is not very reliable compared to pillow or ceramic capacitors.

You can replace the light bulbs with bright LEDs. If a LED consumes 10 mA with 2 V needed power supply the required series resistor is (Vs - Vled) / Iled = (3 V - 2 V) / 10 mA = 100 ohms. You can put additional LED in parallel and reduce the series resistor in half or you can put a few LEDs with 100 ohm resistors in parallel to power transistor.

You only needs three general purpose BJT transistors. However, you have to purchase a few in case you burn them by connecting to wrong pins. General purpose transistors are very cheap.

Rc4 only needs to be a power resistor if you are using light bulbs.

The Rb1 resistor controls to brightness of the light bulbs or bright LEDs.

Step 4: Put the Circuit in a Paper Cup or Box

You can see that the circuit fits in a paper cup.

The light bulbs are attached with sticky tape.

You can make a hole in cup with a screw driver or scissors for the potentiometer.

The lights will be seen through the cup when on.

Step 5: Secure the Wires With Tape

You can use any sticky tape.

Step 6: Attach the Arms and Legs

Use 1 mm metal wire to attach the arms and Legs to the robot.

You are now done.

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