Taffic Light Project

So I'm working on my first "useful" thing with my arduino, and what I want to do is control a traffic light I rebuilt in an interesting way. This is also my first major electronics project, so hopefully I'm not too much of a noob.

I figure for my project I'll need 3 basic circuits:

  • Power - I want to only have one power cord into the traffic light, so have to step down 120v a/c to 5v dc. I'll probably just hide a wall-wart inside somewhere.
  • Input - I'm thinking it would be cool to have the lights dance to music. This is the part I'm having trouble with.
  • Output - I designed a schematic to dim 3 lamps using a zero-point detector and one triac per lamp last night.

So, really I don't know where to begin with the input part. I want to be able to control each light based on the frequency and volume of the sound. So red lights up on bass, and green on treble.

My first thought is to sample mic input with an amp circuit and analyze with FFT. Is this feasible with an arduino? Is there an example somewhere?

My second thought is to rip a circuit out of an existing product. There is a useful salvage shop that has lots of A/V equipment, but I don't know what I'm looking for here either.

Any points in the right direction would be greatly appreciated!

Thanks.

The power from a wall wart is quite reasonable. 12V or 9V supplies are common.

Direct FFT of audio (even into 3 bands) will probably be way beyond the Arduino's computing (and maybe memory) capability. But this is where analog circuitry excels-- you can select out various bands of frequencies and feed each "bucket" directly from inputs.

More info on the triac zero-detecting circuit would be good, someone else on the forum was just trying to work one of those out.

More info on the triac zero-detecting circuit would be good, someone else on the forum was just trying to work one of those out.

Andrew Kilpatrick This site helped tremendously with the design of my schematic.