Converting a traffic light into a color organ

Discussion in 'The Projects Forum' started by mansir, Mar 7, 2009.

  1. mansir

    Thread Starter New Member

    Mar 7, 2009
    Hi guys!

    A few weeks ago my housemates and I went to the dump to get rid of some old crap from the house, and on our way out we spotted the severed "head" of a traffic light. We thought it'd be a great addition to the living room, so we dragged it home.

    Next day we cleaned it and rewired all the lamps to a mains plug, and surprisingly it worked! Only problem is, it shines far too brightly and all 3 lights shine constantly. We had a brainwave and came up with the idea to modulate the intensity of the lights with a musical input. We'd like to make it so that the green light varies with bass frequencies, the yellow light with mid frequencies and the red light with treble frequencies.

    I trawled the internet and finally found this circuit:

    which I then converted to this-

    I wanted to use the optoisolator design for safety etc, but apparently optoisolators require a pretty strong signal to work, so the op-amp section of the circuit is for voltage amplification. After that the signal is split into three, filtered to the desired frequency ranges and passed through the optoisolator. The voltage of this signal then goes into the gate of the triac which controls the brightness of the lamp.

    I've just got a couple of questions now-

    1) Is there anything glaringly wrong with that circuit? I tried simulating it on LTSpice but I couldnt find the triac parts I was looking for so that was fruitless. A quick review from a third party would be great[​IMG].

    2)If you compare the images, you'll see that the original circuit runs from 120V AC, and my adapted one runs from 240V since I'm in the UK. Does anyone know which component values I'd have to change for this to work over here?

    3)Could I replace the Line out input with a microphone input?

    4)Assuming this circuit is right, would it be possible to build it on a breadboard? or maybe have everything up to the triac on a breadboard and the triac just floating?

    Any help is much appreciated, thanks!
  2. bertus


    Apr 5, 2008

    Here is a drawing I used some time ago on the forum.


    The input may come from a microphone.

  3. Johnnz

    Active Member

    Dec 31, 2008
    I'm sure a video of the finished project would go down a treat on Youtube ;) Good luck getting it to go :)
  4. wr8y

    Active Member

    Sep 16, 2008
    Yea, the level of the music will be very critical. (The lights won't blink, but just come on and stay on over a certain level.) But I see the post after yours includes ALC to take care of that!!!

    I made a color organ for a traveling DJ 20 years ago and neither he or I were very happy with it. The human ear can ear much better than circuits like these! A faint drum beat will go unnoticed by the electronics but not by our ears. I ended up giving up and built the guy a keyboard to drive the lights. He had a partner (ya got one guess who that guy was) who "played" the lights like an instrument. I sure met a lot of women doing that!!!
  5. KL7AJ

    Senior Member

    Nov 4, 2008
    I used to have a parking meter and a drive-in movie speaker in my bedroom. And they WEREN'T from the dumpster. Don't tell anyone! :D