What follows are instructions for constructing a battery powered portable VU meter, as well as detailed instructions for the construction of the PCB needed to complete this project. It was designed to illuminate from 0-10 LEDs depending on ambient sound levels. I designed it to be attached to a wristband, clothing, or a necklace if the design is scaled down somewhat. Its purpose is to be worn in a nightclub or similar locale where music is playing, as an animated alternative to a glow stick. It can be used, however, for a variety of alternative purposes.
For this project, you will need the following materials:
1. 1 LM3916 IC
2. 1 LM386 IC
3. 10 LEDs
4. 1 UV Reactive PCB Board
5. 1 18 pin IC socket
6. 1 8 pin IC Socket
7. Various SMT Resistors
8. 1 Dremel tool
9. 1 UV Exposure box
10. Developing chemical
11. Etchant (I use Ferric Chloride)
12. 1 Fine soldering pencil
13. Fine silver-bearing solder
14. 4 3v coin cell batteries
15. 2 Sockets for 2 coin cell batteries each
16. 1 switch
17. 1 electret microphone
18. 3 (1 uf SMT capacitors)
19. Denatured or Isopropyl alcohol
In a pinch some of these components may be purchased from RadioShack but your best bet is to buy them from DigiKey.com or from Fry’s Electronics, or other equivalent local electronics parts retailer.
I created the PCB artwork in a program called Express PCB, which is available for free download and is surprisingly functional. The resultant artwork is pictured on this page. Next, I printed out the PCB artwork on a transparency. When printing the top copper layer of he PCB within Express PCB, the yellow component outlines are not printed, only the red traces are printed. I then cut out the printed portion of the artwork. This will define the size and shape of the PCB. The third picture is a screen shot of Express PCB showing labels for all of the components.
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