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Powering MusicMaker/M0
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Powering MusicMaker/M0

by Virgil_Machine on Thu Apr 27, 2017 5:08 pm

I'm trying to comply with the statement "Don't forget to make sure you have a good strong 5V power supply" in the MusicMaker Feather Wing tutorial.

I assume that means to power the Feather (not the Wing) from a wall wart. That's not feasible for my project. I could use a 4XAA battery pack (I have 2500mAh rechargeables). I do not see the input voltage range for the USB port on the Feather, other than 5V.

So far, it works fine powered from a 3.7V Lipo (not real loud, but the same as USB power). I have a lot more code to write and need to add a servo (with it's own 6V power source).

    Will the 6V cause me a problem?
    Am I missing some other meaning of the "good strong power supply" statement?
    Am I OK with 3.7V?

Thanks for your help.

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Re: Powering MusicMaker/M0

by adafruit_support_mike on Fri Apr 28, 2017 3:19 am

There are a lot of variables that have to be pinned down before you can turn 'good and strong' into a specific number. In general, it means "able to provide the current the VS1053 and its amp need without being subject to voltage spikes big enough to mess up the logic signals."

The Feather isn't designed to work at 6v, but if you'll have a 6v power supply you can use a buck regulator to get a strong 5v rail. Either of these should work:

https://www.adafruit.com/product/1065 - 1A @ 5v
https://www.adafruit.com/product/1385 - 3A @ 5v

The choice between 1A and 3A depends mostly on how much power you want for the speakers.

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Re: Powering MusicMaker/M0

by Virgil_Machine on Fri Apr 28, 2017 3:19 pm

Thank you. It seems to work OK with a 3.7V LiPo powering the board and a 6V battery pack powering the servo.

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Re: Powering MusicMaker/M0

by adafruit_support_mike on Sat Apr 29, 2017 11:55 pm

Glad to hear that's working for you. Some servos are picky about the signal voltage being the same as their supply voltage.

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Re: Powering MusicMaker/M0

by Virgil_Machine on Sun Apr 30, 2017 7:53 am

I'm using the PWM/Servo Feather Wing--without it I had to use a level shifter (one of Adafruit's. of course).

The tutorial says
If using a FeatherWing: Plug the FeatherWing into your Feather. Don't forget you will also have to provide 5V to the V+ terminal block. Check the green LED is lit!
no mention of level shifting, so I assumed that the FeatherWing handled it. I have it working with two different applications.

Do I assume correctly, or am I lucky...or is something else going on?

Thanks.

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Re: Powering MusicMaker/M0

by adafruit_support_mike on Mon May 01, 2017 2:42 am

The servo control signals are the same voltage as the supply voltage to the PCA9685 PWM generator, which would be 3.3v for the FeatherWing.

The 5v servos we carry are okay accepting 3.3v control signals, and it sounds like the 6v servo you're using is also willing to play nicely. That's lucky, but not "drop everything and head to Vegas!" lucky. ;-)

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Re: Powering MusicMaker/M0

by Virgil_Machine on Wed May 03, 2017 3:52 pm

We're getting off the topic of this chain, but here's an update on the servo. The one I'm using is a radio shack standard servo (2730766), 4.8-6.0V. As I mentioned I had it working in a prior version of the circuit without the PWM/Servo Feather Wing, using a level shifter (and the standard Arduino Servo.h library). When I moved to the Feather Wing I no longer needed the level shifter (hence the questions above).

Having learned that I'm lucky, I decided to see what happens if I go back to the prior version without the level shifter. My luck seems to have run out--the servo shimmies and jitters but does not give me the smooth motion I got with the level shifter and with the PWM Servo Feather Wing. In both cases, I have Feather M0 powered from a 3.7V LiPo and the Servo powered by a 4xAA battery pack (with rechargeables).

Everything is as I expected. except that the Servo doesn't mind the 3.3V signals from the Feather Wing when it does seem to mind the signals from a pin on the M0..

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Re: Powering MusicMaker/M0

by adafruit_support_mike on Fri May 05, 2017 1:45 am

That may be related to current more than voltage.

The 32u4 Feather can deliver up to 30mA from each pin, while an M0 is limited to about 9mA per pin.

All wire and all input circuits have some amount of parasitic capacitance, and it takes a burst of current to make them change between high and low. If you use a lot of current, the rising and falling edges will be nice and crisp. If you use less current, the rising and falling edges turn into rising and falling curves, and the lower the current, the slower the curve.

If your servo wants to see a voltage near 3.3v, the M0 might not be able to produce rising and falling edges fast enough to hit the magic number in time.

At this point, I'd hook the boards up to an oscilloscope and see what's actually happening.

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Re: Powering MusicMaker/M0

by Virgil_Machine on Fri May 05, 2017 7:39 am

Thank you.

To be clear: it's an Feather M0 in both cases, with the M0 powered by a 3.7V LiPo

1. I have the music maker and pwm/servo feather wings stacked on the M0, the pwm/servo wing power connections fed by a 4xAA battery pack, the servo connected to one of the 8 servo connections on the feather wing, and the servo responds normally.
2. I have only the music maker stacked on the M0 and the servo power/ground connections to breadboard rails fed by the 4xAA and the signal connection to digital pin 9 on the M0--in this case it works with a level shifter but not without

I don't have an oscilloscope (yet).

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Re: Powering MusicMaker/M0

by Virgil_Machine on Sat May 06, 2017 2:15 pm

Back to the original topic of this thread. I ordered the 5V/2A power supply and the 3A buck converter, and they arrived last night. I powered the Feather M0, and thus the musicmaker, from the new power supply via the USB pin on the Feather.. I notice no increase in volume. I tried using the setVolume method, following what's in the feather_player example

Code: Select all | TOGGLE FULL SIZE
  // Set volume for left, right channels. lower numbers == louder volume!
  musicPlayer.setVolume(10,10);

Several different values from 1-10 yield no discernible difference in volume--am I missing something? Would it be better to use the musicmaker with no amp and supply my own Adafruit class D amp between the musicmaker and the speakers?

Aside: I realized that I overthought this whole thing. The 5V/2A power supply runs both the Feather and the musicmaker, and with a separate connection from the power rails, it powers the servo through the PWM/Servo wing, too. Since I'm using NiMH rechargeables in my 4xAA, I'm getting ~4.8V from that, so I went back to it an powered everything off it: power to the USB pin on the Feather and to the +- terminal block connections on the PWM/Servo wing. Except for the volume everything is fine.

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Re: Powering MusicMaker/M0

by adafruit_support_mike on Sun May 07, 2017 1:11 am

Sorry for the confusion about the 32u4 vs M0.. the same reasoning applies to the output from the Servo FeatherWing's PCA9685 PWM generator. Those can also deliver about 25mA.


.setVolume() accepts values from 0-255, and actually controls attenuation: 0 is loudest, 255 is completely shut off. Each digit represents 0.5db of attenuation, so 0-10 doesn't span a range that would make all that much audible difference. Try some larger values.

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Re: Powering MusicMaker/M0

by Virgil_Machine on Sun May 07, 2017 7:08 am

Thank you.

Re setVolume, I'm trying to make it louder, so 0 is as far as I can go, right? (thanks for clarifying the value range--I did not see that anywhere in the comments or tutorial)

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Re: Powering MusicMaker/M0

by adafruit_support_mike on Mon May 08, 2017 1:22 am

For more volume, you'll probably need a stronger amp, more voltage, or speakers with lower resistance.

What's the impedance of the speakers you're using now?

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Re: Powering MusicMaker/M0

by Virgil_Machine on Mon May 08, 2017 7:39 am

8 Ohm, 1/2 Watt. I've tried a 1.25" cheap radio shack (might be 1/4W) and a 2" that I took out of some device (maybe an answering machine). No difference.
Last edited by Virgil_Machine on Tue May 09, 2017 8:53 am, edited 2 times in total.

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Re: Powering MusicMaker/M0

by adafruit_support_mike on Tue May 09, 2017 3:24 am

Taking headroom limitations into account, you can only get about 1W of output from an 8-ohm speaker. Going to 4-ohm would take the output up to about 3W:

https://www.adafruit.com/product/1314

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