Sound Reactive LEDs

[audioguru]

I assume the resistors would have to be altered for the 9v?

I used 9V because the opamp drives the transistor so that the emitter goes to (the supply voltage minus 2V) which is not high enough (only 3V with a 5V supply) to turn on a white, blue or bright green 3.5V LED.
Use Ohm's Law and simple artithmatic to calculate the resistor value:
1) Find out what is the minimum forward voltage of the LED from its datasheet.
2) The emitter goes to +9V with the switch so subtract the forward voltage and divide by how much current you want (20mA?).
An example is a 1.8V (minimum) red LED. The resistor is (9V - 1.8V)/20mA= 360 or 390 ohms.
Another example is a 3.2V (minimum) blue LED. The resistor is (9V - 3.2V)/20mA= 290 or 300 ohms.
You cannot connect two blue LEDs in series because their max forward voltage might be 3.5V then they won't have enough voltage across the resistor since the emitter is +7V when driven by the opamp.

1) (havent got that type of switch in my app but thats the rough idea!)

You said you have a 3-positions switch: On-Off-On. In the off center position then the battery is connected to nuttin.

 

[Sizer]

Thanks for that, they are 3v forward, so 300ohms should do it. I do have the switch I just cant represent it in the diagram as the app I use doesnt have one.

I got all the parts today, only problem is I missed one out

Is there a way to replace the 0.33uf Capacitor as I only have the following ones :

4 x 100nF ceramic.
4 x 1uF electrolytic.
4 x 10uF electrolytic.
2 x 220uF electrolytic.
10 x 10nF Ceramic Disc capacitors.
10 x 100nF Polyester box capacitors.
10 x 1uF Electrolytic capacitors.
10 x 10uF Electrolytic capacitors.
10 x 100uF Electrolytis capacitors.
3 x 220uF Electrolytic capacitors.
3 x 470uF Electrolytic capacitors.

If not ill have to order one, was just hoping to get it running tonight.

 

[audioguru]

If the pot is 100k then a 100nF poly capacitor produces a cutoff frequency of 16Hz which is fine.

 

[Sizer]

Wicked!! Just got to try and get it on the breadboard now then!

They should really make a prog that translates it for you...

Thanks for all your help, Ill keep you posted with the results

 

[Sizer]

Well results so far are 10 very dim LED's and not alot else...just trying to check through it all

 

[Sizer]

Update, got it working but doesnt react quite as I expected. When adjusting sensitivity theres not alot in it, its either off or on, the LEDs do flash but not as responsive as I expected. Even loud if its just vocals, no LEDs only when the bass kicks it do you get the lights going. (and damnn that POTs sensitive!)

Also I swapped the Chinese Purple Ultra Bright LEDs out for some UK Ultra Bright Blue ones (much brighter) 5mm BLUE, 8500mcd 3.3Vf Ifmax=25mA and when i did that they stayed on permanently??

 

[audioguru]

Update, got it working but doesnt react quite as I expected. When adjusting sensitivity there's not alot in it, its either off or on, the LEDs do flash but not as responsive as I expected. Even loud if its just vocals, no LEDs only when the bass kicks it do you get the lights going. (and damnn that POTs sensitive!)

The gain is 101 times so it should be fairly sensitive. Maybe that expensive no-name-brand mic is garbage.
What is the value of your volume control pot?
Maybe the transistor has its pins connected backwards.

Also I swapped the Chinese Purple Ultra Bright LEDs out for some UK Ultra Bright Blue ones (much brighter) 5mm BLUE, 8500mcd 3.3Vf Ifmax=25mA and when i did that they stayed on permanently??

A purple LED is almost an ultra-violet one that is invisible.
See my attachement. When there is no sound then the output to the LEDs is ZERO VOLTS so how can the LEDs stay on permanently?

Oh. Maybe you are using a breadboard and the millions of messy long jumper wires are antennas that pickup mains hum.

 

[Sizer]

I had a wire wrong, works a treat now. Certainly off the PC/AMP, where the volumes pretty loud, tried it off the TV and its not sensitive enough really but does still work. The best bit is I almost understand all of the circuit thanks to your help so I'm chuffed to nuts. So next mission is to make it up properly and get it to work on the xmas tree.

Got to be said though the 18000 mcd purple LED's are pants, anyone thinking of buying off ebay....save yourself a fiver.....they are a waste of money. Putting the blue next to the Purple Ultra Bright...I'd say the Ultra Bright Blue are 4x brighter. So buy from a reputable person with the datasheet rather than a Chinese person guessing at random numbers.

For anyone interested heres a vid : https://www.youtube.com/watch?v=Bj6C5EHI_FM&list=UUwU0TL8VRkjk18A17-Z3_7A&index=1&feature=plcp

 

[audioguru]

You are correct, it is not sensitive to sound levels. Only the loudest parts (the beat) turn on the LEDs.
If you reduce the value of the 1k resistor at the opamp or increase the value of the 100k resistor connected to it then the circuit will be more sensitive.

 

[Sizer]

That dome the trick, 100 to 300k is about perfect....works a treat. No to get it all onto a proper board thenfigure out how to wire it up to the xmas tree LEDS