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Converting a traffic light to a disco light

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mansir

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Hi guys!

A few days ago my housemates and I went on a night out, much drunkenness etc occurred and on our way back we spotted the severed "head" of a traffic light in a skip. In our drunken stupor 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 had a root around on the internet and found that the easiest way to do this would be to:

1) solder some wires onto the connector wire between the ipod and the hifi to get the musical output

2) split this into 3, one for each light, then bandpass filter the signal to get it to the desired frequency range

3) rectify this signal to get a DC output voltage depending on the signal strength of the music in that frequency range.

4) Use this voltage to trigger a triac used as part of a dimmer switch circuit

This makes a lot of sense as a general idea but I'm having a bit of trouble fully designing the circuit as my knowledge of electronics is pretty basic!

I had a bash at designing something, see the attachment (excuse the crappy mspaint)


As far as I can tell, the voltages across the 3 diode bridges should be fully rectified copies of the music, filtered to the frequencies I select via the RC value of the filters. The trouble I'm having is I'm unsure how to connect this to the triac that's connected to the mains. The areas I'm talking about are circled in red on the diagram. There are two outputs from the rectifier and the triac gate is only one input, and I'm not too sure what I need to do. Like I said, my electronics knowledge is pretty basic and I'm probably missing a load of stuff on this so if anyone could have a look over this and point out where I'm going wrong and what I need to do it'd be much appreciated. Thanks!
 

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Google for color organ. You may need to add bigger SCRs or TRIACs to whatever project you find if the traffic light draws a lot of current.

Your link is duff:
**broken link removed**
403 Forbidden
nginx
 
Hi again!

I trawled the internet and finally found this circuit:

**broken link removed**

which I then converted to this-

https://i43.tinypic.com/2ez69f5.jpg

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:).

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?

Any help is much appreciated, thanks!
 
Sadly I can't help you with the electronics but this looks like an awesome project. Could you post some videos of it if/when you get it working?
 
1) Is there anything glaringly wrong with that circuit?
Nothing really. Did you take into consideration the resistance of R2, R6 & R9 when designing the filters? If not, your frequency cutoffs will not be as expected.
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?
You should probably use the MOC3052 or other Opto which has a VDRM of 600V or more. The VDRM of the MOC3021 is 400V which is pushing the safety margin a bit on 240VAC. I assume the BTA-600B has a blocking voltage of 600V also.
3)Could I replace the Line out input with a microphone input?
Probably not without a mic preamp. You can use an OpAmp for that.
 
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