Sound Activated Light Circuit

In summary: If it is too bright, then the transistors will probably not work. Cathode tubes can be quite bright when used in this way.
  • #1
DoomDuck
9
0
Hello,

I am currently working on a music reactive light system with LEDs, but due to the low amount of light produced by the LEDs I was hoping to incorporate cathode tubes commonly found in desktop computers. I tried amplifying the signal from my mp3 player where the base current was produced by the player and the cathode's inverter was connected to a TIP31B transistor with a 12 V source. This produced a very low amount of light but the light did beat to the music, to a degree. I tried to use multiple transistors but that failed and surprisingly induced no light. Then opened some old computer speakers and tried to use the leads to the speaker as the base current but this produced no effect at all despite the higher current. Strangely when the ground of the inverter came into contact with the positive lead of the speaker and then the leads were placed in the circuit, the cathode would briefly light up and beat with the music but then slowly diminish until this ceased.

I am a bit baffled at both why multiple transistors and the speakers didn't work. This is my first experience with inverters, are there any special considerations with them?

Thanks,
Duck

These are the cathodes:
http://www.xoxide.com/bluecathode.html
 
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  • #2
If it helps, the circuit set up is similar to this except in place of LEDs there is an inverter attached to the cathode tube. As stated earlier, that works but poorly. The 12 V is supplied by a modified computer power supply that acts as a bench top power unit, so the dc voltage being used should be very clean with regard to its signal.

This image is originally from:
http://www.instructables.com/id/Music-LED-Light-Box/step6/Building-the-circuit/
 

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  • #3
If you put a lamp or a LED (in series with a protective resistor) across a 12 volt supply, that is as bright as it is going to get. Adding a transistor in series with it will only make it dimmer.

The transistor acts like a variable resistance in series with the lamp or LED and gives you control over the device, but it can't make it brighter.

A PNP transistor like the TIP31 should not have its base grounded because this would cause its base current to be very large and it may destroy the transistor. The output of an amplifier is usually through a capacitor, so this probably saved your transistor.
You would need to have a suitable resistor in circuit from base to ground and then feed the input via a capacitor onto the base.
A suitable resistor might be 100 K, but you would have to check this by trying it. Make it smaller to send more current through the LED. You can also reduce the size of the 470 ohm resistor, but this is at some risk of letting too much current pass through the LED. Most LEDs will only cope with about 20 mA.
[PLAIN]http://dl.dropbox.com/u/4222062/NPN%20%20LED%20AMP.PNG [Broken]

Your cold cathode devices have an internal high voltage supply, so this is probably set up to be self protecting. Again, connect the device across 12 volts (observing polarity carefully) and that is as bright as it is going to get. If it is bright enough to be useful, then you can try to control it with transistors.
 
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1. What is a sound activated light circuit?

A sound activated light circuit is an electronic device that uses sound waves to trigger the turning on and off of lights. It typically consists of a microphone or sound sensor, a control circuit, and a set of lights or LEDs.

2. How does a sound activated light circuit work?

The sound activated light circuit works by detecting changes in sound levels through the microphone or sound sensor. When a sound above a certain threshold is detected, it sends a signal to the control circuit, which then activates the lights connected to it. The lights will remain on until the sound levels decrease below the threshold.

3. What are the applications of a sound activated light circuit?

A sound activated light circuit can be used in various applications, such as in disco or party lights, stage performances, security systems, and even as a fun DIY project. It can also be used to visually represent sound levels in music or other audio recordings.

4. Can a sound activated light circuit be adjusted for different sensitivity levels?

Yes, most sound activated light circuits come with adjustable sensitivity levels. This allows the user to adjust the threshold at which the lights will be triggered, depending on the environment or their preference.

5. Are there any safety precautions to consider when using a sound activated light circuit?

Yes, it is important to make sure that the sound activated light circuit is properly installed and wired according to the manufacturer's instructions. It is also recommended to use caution when handling electrical components and to disconnect the circuit from power before making any adjustments or repairs. Additionally, avoid exposing the circuit to excessive moisture or extreme temperatures to avoid damage.

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