Got to love circuits that flash and make noises when you are showing electronics to young people. These five circuits that take just a few minutes to build, they are easy to modify in order to change the flashing speeds or on times.

The first circuit is a little different and a fun treat but first to parts.

Supplies

Parts and Supplies

I have a few extra parts like capacitors just to change the speeds of the flashers and the on times.

3 x 100 Ω

1 x 330 Ω

2 x 470 Ω

3 x 10 KΩ

1 x 1 MΩ

1 x 1 KΩ pot

2 x 0.01 uF

2 x 0.1 uF

2 x 1 uF

2 x 100 uF

2 x 1000 uF

4 x BC547

1 x BC557

2 x 2N3904

1 x Chip RGB LED

4 x LEDs Any Color

1 x Momentary Button Switch

1 x Piezo Buzzer

Batteries or an adjustable power supply.

9 Volt Battery

9 Volt Battery Holder

3 x AA 1.2 Volt Rechargeable Batteries

1 x 3 x AA Battery older Bread Boards

If you make permanent circuits you will need prototype boards, a soldering iron, solder, and cutters, to remove excess leads.

Step 1: Beeping RGB LED

This first circuit is a real neat circuit, it uses the changing current of the chip RGB LED to make the piezo buzzer buzz with different tones as the LED changes color.

Parts

1 x chip RGB LED

1 x Piezo buzzer

1 x BC547 transistor

1 x 100 Ω

1 x 330 Ω

9 volt battery and holder Wire and bread board.

Step 2: Delay Circuit

This circuit will keep the LED on until the capacitor losses its charge. With this circuit I could change the brightness and the on time with different valued capacitors, resistors, and transistors.

Parts

1 x 100 Ω

1 x 10 KΩ

1 x 1000 uF

1 x 2N3904

1 x LED Any Color

1 x Momentary Button Switch

3 x AA 1.2 Volt Rechargeable Batteries

1 x 3 x AA Battery older Bread Boards

Step 3: Dimmer Circuit

This is a nice little circuit to demonstrate controlling an LED with a pot and a transistor.

Parts

1 x 100 Ω

1 x 2N3904 transistor

1 x 1 KΩ pot

1 x LED Any Color

9 volt battery and holder Wire and bread board.

Step 4: Flasher

This circuit is very forgiving and east to change the speed of the flashing by changing the value of the capacitor.

Parts

1 x BC547

1 x BC557

1 x LED Any Color

1 x 1 uF

1 x 1 MΩ

9 volt battery and holder Wire and bread board.

Step 5: Flip Flop Flasher

This is a very forgiving circuit; you can put the capacitors in backwards and the circuit works, you can also change the flashing speed by changing the capacitor values.

Parts

2 x 470 Ω

2 x 10 KΩ

2 x 100 uF

2 x BC547

2 x LED Any Color

9 volt battery and holder Wire and bread board.