rvalkass 5 Report post Posted July 10, 2010 I recently decided, to fill the time, that I would try to make a small device that flashed LEDs in response to sound or music. This should be a helpful guide to the components and circuit to build the same device. It's also fairly easy to adapt to different sound sources or light outputs. It has two sockets, one for audio input and one for audio output, so you can connect your speakers to the device and still hear your music/sound. Bill of Materials Codes refer to Maplin product codes. Stripboard / Veroboard - N95CF - http://www.maplin.co.uk/?ModuleNo=47480&2xAA battery holder - YR60Q - http://www.maplin.co.uk/?ModuleNo=31427&SPST rocker switch - YX64U - http://www.maplin.co.uk/?ModuleNo=2365&Blue LEDs (x9) - JA24B - http://www.maplin.co.uk/?ModuleNo=12703&3.5mm stereo jack sockets (x2) - FK03D - http://www.maplin.co.uk/?ModuleNo=1189&TIP31C NPN transistor - UM82D - http://www.maplin.co.uk/?ModuleNo=19066& I sourced all of the components from my random collection of electronics parts I've gathered over the years except for the jack sockets and the veroboard (as I'd run out). Both of those were purchased from eBay very cheaply. I have also seen the jack sockets on sale in Maplin (although at a slightly higher price). Circuit Diagram NB: Not shown - connect the input left channel to the output left channel too. How it Works As the sound level varies on the input, the signal reaching the base of the transistor varies. This causes the current flowing from the collector to the emitter to vary with it, causing the LEDs to blink along with the music. They switch on with loud base nots, and switch off for quiet sections. Improvements As the LEDs I used were rated 25mA@3V I connected them in parallel with 2 AA batteries. This allows the device to work with no external power source, so it's useful with portable music players when out and about, for example. However, these LEDs are not bright enough to really stand out (I also only had water clear ones rather than diffusing ones to hand). I also intend to fit the device into a case, mounting the switch and audio sockets so it looks much neater and is easier to move around, but that will have to wait until I have access to a drill again. If people are interested I can put my veroboard layout up, and a video of the device in action Share this post Link to post Share on other sites
