Name: Class: FMT-105

Spr. 2015

Class Project: Rain Sound Generator – Sleep Aid in Case of Insomnia

1. Project objective: build a circuitry that generates a rain sound effect.Insomnia treatment consists mostly of sleeping pills consumption but thiscircuit is an alternative for that and consists of a simple circuitry thatgenerates a rain sound effect. The Japanese researches were the first todiscover that sound of rain has a relaxing effect. With the help of thissimple circuit we can generate the rain sound which can be a sleep aid incase of insomnia.

2. Why I chose this project:I found this circuit on the Internet. Someone said the rain sound has arelaxing effect. It is not easy to generate the rain sound with a simplecircuit. However, I try to build this circuit and hope the sound generates bythis circuit has an actual relaxing effect.

3. Circuitry:

T1 is used as a noise generator and its signal is amplified by the 741 IC and thru T2, R7 and C4 goes to a headset with low resistance. If you do not want to use the headphones then use a speaker with impedance between 4 and 16 Ω. With the help of P1 can adjust sound level and with P2 the tone.

4. How do I build it: I use a prototype PCB, and mount electronics components on it. Because I use a small speaker, the sound is very small. I have to modify the circuit, adding one transistor amplifier (T3). Finally, I can hear the sound on a small speaker.

The sound generates by this circuit is not the natural rain sound. When I try to make it louder, it does not make me relax. However, when I adjust the sound barely audible, I have a feeling of comfort.

Pins description:

Op Amp 741 Op Amp 741 DIP-14pin DIP-8pin

Modified circuit:

- 4

5

10

11

6

+

VCC+

VDD-

- 2

3

6

7

4

+

VCC+

VDD-

- 2

3

6

7

4

+

VCC+

VDD-

VCC +9V

VDD -9V

220Ω

2N2222

2N2222

speaker

220Ω

4.7K

4.7K

10µF

47µF

T2

T3