sound reactive LED help

[carlman14]

hi, i have just set up a system with sound reactive leds in the speakers. they work... but the music has to be really loud for them to work. i know that transistors can be used to amplify current. that helped a little. is there any way i can REALLY boost the current or something else that allows me to have my super awesome leds work without music that my neighbors can hear inside their house?

thanks a bunch.

ps. i am also new to this stuff and this is my first bigger project with leds.

 

[J_C]

Start by showing us a schematic of the whole circuit as you presently have it, and a basic description.

Generally speaking, if you want to boost it more you just need yet another transistor being driven (at it's base) by the present one, though I would also wonder if your mic isn't sensitive enough or do you have direct wired (audio) signal to the circuit?

There are other options, depends on how elaborate, your skill level, expense, etc. Briefly a simple gain stage could be had with a typical opamp.

 

[carlman14]

ok so basically, all the anodes are connected together with wire, and so are the cathodes, in the form of a circle.

on the cathode end is the negative power source.

on the anode end is the negative audio signal (from the speaker wire that runs all around my room) and the emitter of the transistor.

connected to the base of the transistor is positive audio signal.

connected to the collector of the transistor is the positive power source.

sorry, but thats the best i can explain it. if i knew how to put up a picture here i would do it. with all this being said, is there any specific way i should go about this? keep in mind that i am a beginner.

 

[JohnR66]

You would want to use the line out as the signal source as it is not dependent on the volume setting. You should use a bias circuit on the transistor to give it the proper amplification for the job intended. In this case I think you would want the transistor to trigger a digital gate that turns the LED on and off to the music. I would use a low pass filter as you probably want the LEDs to flash to the beat of the music (drums). The device would need a level control as music is not always recorded at the same level or bass level.

The 555 timer could be used in monostable mode. It has sufficient output drive for the LEDs which would eliminate the need for a driver transistor on the output of an ordinary logic gate.

 

[carlman14]

ok, so i have never worked with a low pass filter or a 555 timer... because i literally just picked up this whole circuitry and LED stuff like a week and a half ago. i'm sure this is basic, and i am a fast learner, but could you explain how i would use those to amplify the current, in as simple terms as you can? also, what is a bias circuit? thanks a bunch and sorry for being such a newbie.

 

[JohnR66]

A simple low pass filter is a series resistor followed by a capacitor connected to ground. The resistance (impedance) and capacitance determine the frequency roll-off. A network of resistors used with transistors are used to set the gain (amplification) and bias (a small base current used to get the transistor conducting). The bias current value or lack of any bias depends on the circuit design.

Okay, enough of the tech talk. I assumed you had more knowledge of this stuff since you were talking transistors and such. I can't give a lesson here. Books are written on the subject and may require prerequisite knowledge. Electronics is a fun hobby. Why not check out a few books and be well on your way to design some fun and useful circuits?

 

[carlman14]

yeah, i'm really liking this hobby. i will look in some books soon and learn a bit before i do any more on this, cause i think i'm a little over my head at this point. is there any good books that you know of that can start me off well?

 

[JohnR66]

Any introduction to electronics book will be good. It will take you through the different components. You will need to perform some basic algebra to handle the calculations. A textbook format is better as it will give you some questions to practice on.

Get yourself a protoboard (breadboard) and components to apply your knowledge. For example, calculating the current through a resistor given a certain voltage is important, but setting up the same circuit and actually measuring the current offers some satisfaction in the learning process (not to mention hones your breadboarding skills).

Lastly, don't short change yourself on equipment. You don't need to spend a lot, but a meter that measures, voltage, current, resistance, capacitance, frequency and such is very useful. As you progress, be sure to consider an oscilloscope. It is perhaps the most critical tool when delving into oscillating circuits.