0

VU meter with Music Maker shield
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

VU meter with Music Maker shield

by alecwaters on Mon Oct 20, 2014 5:56 pm

Hello,

I've seen other projects where a VU meter has been made by calling analogRead() on a pin attached to an audio source (like a 3.5mm jack, or indirectly via an amplified electret mic).

Is there somewhere on the Music Maker I can tap to achieve the same thing? The line out socket somehow?

Many thanks,
alec

PS - the "resistor" captcha on this forum is tricky when one is colour blind :)
User avatar
alecwaters
 
Posts: 17
Joined: Tue Oct 01, 2013 10:55 am

Re: VU meter with Music Maker shield

by adafruit_support_mike on Tue Oct 21, 2014 2:18 am

If you have the version without a class-D amplifier to drive speakers, you can pull the left, right, and GND signals from the pads that would provide input to the amp:

1790-04.jpg
1790-04.jpg (61.26 KiB) Viewed 505 times

Otherwise, you'd have to take the signal that comes out of the headphone jack.

adafruit_support_mike
 
Posts: 55341
Joined: Thu Feb 11, 2010 2:51 pm

Re: VU meter with Music Maker shield

by alecwaters on Tue Oct 21, 2014 6:14 am

Thanks Mike.

I've got the amplified version, so I'll have to take it from the headphone jack.

Is it safe to go straight from the L and R connections to analog pins? Or do I need to treat the signal somehow before it gets there?

Many thanks,
alec
User avatar
alecwaters
 
Posts: 17
Joined: Tue Oct 01, 2013 10:55 am

Re: VU meter with Music Maker shield

by adafruit_support_mike on Thu Oct 23, 2014 9:58 pm

The headphone outputs are decoupled through 220 microfarad capacitors, which leaves the signals 'floating'.. independent of the Arduino's VCC and GND rails. You need a current path to a known voltage to guarantee the signals stay in a range where you can measure them.

Make a couple of 10k-10k voltage dividers between VCC and GND, and connect each output to the center of a divider. That will give you an AC signal centered at 2.5v.

adafruit_support_mike
 
Posts: 55341
Joined: Thu Feb 11, 2010 2:51 pm

Re: VU meter with Music Maker shield

by alecwaters on Thu Oct 30, 2014 7:56 am

gravestonefinal.png
gravestonefinal.png (119.64 KiB) Viewed 478 times
Thanks Mike.

In the end I used a Sparkfun Spectrum Shield (I know, a competitor's product!)

The end result is this (the spectrum shield kicks in at about 40s):

http://youtu.be/0xwMbbmw55Y
User avatar
alecwaters
 
Posts: 17
Joined: Tue Oct 01, 2013 10:55 am

Re: VU meter with Music Maker shield

by adafruit_support_mike on Thu Oct 30, 2014 2:23 pm

Whoa.. *nice* build!

Since I know everyone who sees the video will ask, could you give a quick explanation of how you covered the LEDs to make them invisible when they're off?


BTW - the folks from Sparkfun are our friends. Any 'competition' between us and them is on the order of "who's going to get that next star in Mario Kart?"

adafruit_support_mike
 
Posts: 55341
Joined: Thu Feb 11, 2010 2:51 pm

Re: VU meter with Music Maker shield

by alecwaters on Thu Oct 30, 2014 5:11 pm

Hi Mike,

Thankyou :)

The gravestone is just paper stuck to card, and the Arduino etc is in an enclosure fixed behind it. The card has a cut-out in the middle that goes around the enclosure like a lion's mane. This means that there's only paper over the front of the enclosure where the LEDs are mounted - they just shine through the paper when they're on!

alec
User avatar
alecwaters
 
Posts: 17
Joined: Tue Oct 01, 2013 10:55 am

Re: VU meter with Music Maker shield

by adafruit_support_mike on Fri Oct 31, 2014 3:28 pm

I like it.. simple, elegant, and easy to customize.

Once again, kudos for an excellent build.

adafruit_support_mike
 
Posts: 55341
Joined: Thu Feb 11, 2010 2:51 pm

Please be positive and constructive with your questions and comments.


cron