Tuesday, 9 August 2011

Audio level triggering device


This is Dr Harry Witchel. A doctor no less. He's a scientist specialising in Neuroscience and Psychobiology. We've always found stuff to do with thinking and the brain to be quite fascinating (hey, this isn't called Nerd Club for nothing!) so were thrilled when one of us met up with him recently to discuss helping out with a project he's working on.

The full brief is here but the basic idea is this:
Harry needs a device that he can connect to the audio out of a PC and will trigger a number of outputs when it detects a loud sound. The threshold volume of the input sound needs to be selectable via a potentiometer or similar rotary dial. The same device needs to display what is happening through a series of coloured LEDs and have a number of operational modes selectable through a series of buttons.

It's just crying out for a microcontroller.
And not just any microcontroller, but our old friend the PIC 18F2455.
Using a number of analogue-to-digital pins, digital inputs and outputs and a few discrete components, we could even create a USB-compatible device that can display exactly what is going on, in a nice onscreen display - not just a few twinkling LEDs!

Here's Harry's original spec with our comments in red:
Specifications for Audio Trigger


Here's the first version of the circuit diagram to acheive what he's after:
Audio Input Circuit

We're hoping to have a working version of this circuit (on a breadboard at least) in time for next Thursday's BuildBrighton meeting. More details (and photos) will be posted here in good time.....