Currently I am in the process of designing the PCB layout for the Music and Lights system. I am using KiCAD for designing the layout. I want to do a really good job on the layout because as observed on the bread board prototype, this circuit is very susceptible to interference.
In the meantime, I thought I should write a blog post about the first Music and Lights system I built. Yup, that’s the one on the image at the top of this page. I called it the MSYNC.
It has two 32ohm speakers driven by classic LM386 audio amplifiers. Each speaker has 20 LEDs around them; 10 green and 10 red leds. These LEDs are driven by LM3914 led drivers. The red lights show the bass level and the green lights show the treble level of the input audio.
On the front side, there are 10 RGB LEDs showing the bass and treble levels. At maximum bass (when all 10 red LEDs are lit) a blue lights goes across the front LED bar. I will explain how it works in detail in just a bit, but first lets see it in action!
Unlike the Music and Lights system I am building right now, MSYNC is completely analog. It has no microcontrollers. Also MSYNC uses passive filters made from resistors and capacitors unlike the new system, which has active filters made from op-amps.
It is made with two double sided PCBs stacked together separated by an insulated layer (I used a sheet of plexiglass). The top PCB has the speakers, speaker amplifiers, filters and the LEDs around the speaker (see schematic below). In order to conserve space I decided to place the speakers on top of the LM3914 LED driver chips with a bit of insulation.
The second PCB controls the 10 RGB LEDs on the front. With the help of a LM555 timer IC, a set of shift registers poll the state of the LM3914 output pin that corresponds to maximum bass level at regular intervals. When the maximum bass is registered, the blue LED connected to the first output pin of the shift register is turned on. This value then gets shifted out of the shift register on subsequent readings, which results in a blue light moving across all ten RGBs.
The schematic below shows how the components in the second PCB are connected.
Now I could get into how I made the PCBs at home and how I assembled everything in a plexiglass box, but it would take many more blog posts to explain everything. There will surely be a post about how I make PCBs at home in the future.
Thanks for reading! If you have any questions please comment.