Go Down

Topic: VU meter (Read 995 times) previous topic - next topic

funkyguy4000

Hello!
http://hacknmod.com/hack/led-light-box-thumps-to-your-music/
I'm trying to make that!
But i have issues
1)I want to use a socket instead of a plug
2)I don't have a 12v battery, I want to run it at 5v
3) I want to run a lot of leds, so i need to wire it up in parallel

GO NOW ARDUINO FORUMS! DO MY BIDDING!! MUAHAHAHA!
no but really, I've been trying to work on this alllllll day, which means over 10 hours! I NEED HELP!!
Please help :)
Accelerate to 88 miles per hour.

James C4S


1)I want to use a socket instead of a plug

Okay, that should be an easy change.


2)I don't have a 12v battery, I want to run it at 5v

Looks like the circuit relies on the LEDs to have a 3V forward voltage.  There really should still be a current limiting resistor in the design.  Since the LEDs are not addressed individually, you could use a 5V supply and put them in parallel instead of series.
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

funkyguy4000

Okay, I'll try that again.  I think my tip31 is burnt out or some crap like that
Accelerate to 88 miles per hour.

James C4S


Okay, I'll try that again.  I think my tip31 is burnt out or some crap like that


That could happen if you used LEDs without a current limiting resistor... ;)
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

funkyguy4000

well the diagram doesn't say to use a resistor
what value would i even use?
Accelerate to 88 miles per hour.

James C4S


well the diagram doesn't say to use a resistor

Not everything on the internet is correct.

That circuit relies on the power supply to act as a constant current supply, which isn't a good idea.  When a LED has its forward voltage dropped across itself, it effectively turns into a short circuit.  This is why you use a current limiting resistor.  The voltage drop of the LED is constant.  This means the voltage dropped across the resistor is constant and there is a linear relationship of voltage and resistance with a resistor.  This will create a constant current through the resistor.  Since the resistor is in series with the LED, it limits the amount of current the LED draws.


what value would i even use?

Depends on the maximum current allowed by the LED, how bright you want it, and how much current is available by your supply.
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

Magician

Schematic posted on hacknmod is good example how NOT to do.
Use this one instead:
http://arduino.cc/playground/uploads/Learning/multiple_leds2.jpg

funkyguy4000

How would that one be changed so that you could use it for the audio input?
all of them are arduino....
Accelerate to 88 miles per hour.

Magician

Connect to audio output , line level and up. Speakers (< 2 W) and headphones outputs should be o'k too.

funkyguy4000

Ah the only thing i want this meter to do with the arduino is the ground and +5,
I want to still use the tip31, its just using it properly. I know how to change the wiring so its parallel but i dont understand why it won't work.

...in my first diagram, it says left OR right, can i just put both on that pin?
Accelerate to 88 miles per hour.

James C4S

The original diagram was meant to be connected to an audio source, 12 volt battery, and 4 LEDs.

You're using "lots of LEDS", a 5V supply, and an Arduino as the source.  At what point are you going to realize this circuit has nothing to do with what you are trying to do?
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

Magician

Yes, you can put both. Type of transistor doesn't matter much, as long as its V-I spec.  not exceeded.

funkyguy4000

Quote
The original diagram was meant to be connected to an audio source, 12 volt battery, and 4 LEDs.

You're using "lots of LEDS", a 5V supply, and an Arduino as the source.  At what point are you going to realize this circuit has nothing to do with what you are trying to do?


I think you a little butt-hurt because you don't understand what i'm trying to convey, probably my fault.  Thank you for your help thus far.

Quote
Yes, you can put both. Type of transistor doesn't matter much, as long as its V-I spec.  not exceeded.


Alright then, I think i'm just going to do a all-or-nothing run.  Coming off of the breadboard and off to the soldering iron.  wish me luck!
Accelerate to 88 miles per hour.

Go Up