Sound Activated LED's

[wej9547]

I have been researching ways to make an array of around 300 LED's that would be sound activated. After looking through previous forums I found this particular one to be very helpful Wiring 500 or more LEDs: Parallel of Series? However having only taken a few electrical engineering courses in college I am not 100% confident in wiring with 120V.

Basically I am trying to recreate something like THIS but with 300 LEDs and be able to plug it into a standard American wall outlet. My original plan for the audio input is a 3mm audio cable. The LEDs I will be using are 5mm blue LEDs, 3.5V, 20mA. Any advice would be greatly appreciated.

Thanks

 

[Helmut.G]

Get a mains adapter that puts out a safe voltage and wire the LEDs to that.

btw instead of using 300 crappy 5mm LEDs it could be easier to use a couple of high-powered ones.

 

[wej9547]

Using a lower voltage power supply would solve the safety issue for sure and any AC DC conversion, but would also mean using more current to supply all of the LEDS right? This is assuming I use a 12V supply with 3 or 4 groups of 75-100 LEDs wired in parallel.

The reasoning behind using 120VAC was to make many small groups of LEDs and eliminate the need to buy a power supply.

My other question would be how to make the lights flash to sound. To do this I think I need a transistor wired in somehow. What transistor would be good for this application and where would it be wired in? And could I use a transistor to amplify the current out of a 12V power supply?

 

[Helmut.G]

Using a lower voltage power supply would solve the safety issue for sure and any AC DC conversion, but would also mean using more current to supply all of the LEDS right? This is assuming I use a 12V supply with 3 or 4 groups of 75-100 LEDs wired in parallel.

The reasoning behind using 120VAC was to make many small groups of LEDs and eliminate the need to buy a power supply.

My other question would be how to make the lights flash to sound. To do this I think I need a transistor wired in somehow. What transistor would be good for this application and where would it be wired in? And could I use a transistor to amplify the current out of a 12V power supply?

Yes you'd need more current at the lower voltage but it's the best solution because you can't just wire some LEDs to the grid and hope it works.
First, the voltage is dangerous.
Second, it's AC so the voltage varies between like -150V and +150V 60 times a second, it's not like you wouldn't need any circuitry to protect your LEDs.

And yes, of course you need a transistor, like shown in the circuit diagram you linked to.
The transistor that switches the LEDs' current needs to be big enough to stand the power.


I don't see why you'd want to wire up 400 LEDs.
You could use 12 power LEDs, four strings of 3 LEDs and get about the same brightness.