I can hear my gemma on my Audio FX.

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ShaunDarkLord
 
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I can hear my gemma on my Audio FX.

Post by ShaunDarkLord »

Hi All

I'm working on a small project using a Gemma to control some NeoPixels and an Audio FX (+ 2x2W Amp) sound board to play sound files. I'm using a single 5V power source, and have buttons connected to trigger actions on both the Gemma and the soundboard.

Everything is working, but I can hear the Gemma's NeoPixel output through the speakers. I assume this is because I have a common power source and am getting some kind of feedback?

What is the best way to prevent this from happening? I need a common ground so that the buttons work on both boards, and I'd prefer to not have to crack open the 5V power supply.

Thanks

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adafruit_support_bill
 
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Re: I can hear my gemma on my Audio FX.

Post by adafruit_support_bill »

You do need a common ground. But try to use separate power and ground wires for the analog part of the circuit. That will help isolate them from the current fluctuations of the Neopixels. You can also add some capacitors between 5v & gnd close to the Audio board. A .1uF ceramic cap and whatever size electrolytic you can fit in the space available.

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ShaunDarkLord
 
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Re: I can hear my gemma on my Audio FX.

Post by ShaunDarkLord »

adafruit_support_bill wrote:You do need a common ground. But try to use separate power and ground wires for the analog part of the circuit. That will help isolate them from the current fluctuations of the Neopixels. You can also add some capacitors between 5v & gnd close to the Audio board. A 1uF ceramic cap and whatever size electrolytic you can fit in the space available.
Thanks very much.

What would be the ideal sized electrolytic capacitor (I'll make space) and should the capacitors be in series or parallel?

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adafruit_support_bill
 
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Re: I can hear my gemma on my Audio FX.

Post by adafruit_support_bill »

The capacitors should be wired in parallel. The ceramics react faster to short transients. The electrolytics are slower but have the capacity to smooth over larger fluctuations. The 'ideal' value is somewhat dependent on the specifics of your circuit and neopixel activity. The rated voltage should be 5v or more. Something in the 200uF range would be a good place to start: https://www.adafruit.com/product/2192

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ShaunDarkLord
 
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Re: I can hear my gemma on my Audio FX.

Post by ShaunDarkLord »

Thank you - I shall give it a go tonight.

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ShaunDarkLord
 
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Re: I can hear my gemma on my Audio FX.

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adafruit_support_bill
 
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Re: I can hear my gemma on my Audio FX.

Post by adafruit_support_bill »

Nice looking Arc Reactor! Thanks for the video.

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mrhume
 
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Re: I can hear my gemma on my Audio FX.

Post by mrhume »

Hello,
I'm having this same problem, and I see that the solution is to use the capacitors you linked to smooth out the current, but I'm sorry to say I'm such a novice I don't understand the wiring instructions. Do I just solder the two capacitors to the wires running into the audio fx board? And if so, do I attach them across the power and ground, or do they go on one side only? I'm sorry these are such basic questions! Thanks for your patience.

Thanks very much for your help!
Josh

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Franklin97355
 
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Re: I can hear my gemma on my Audio FX.

Post by Franklin97355 »

According to the other post you would wire a 200uF electrolytic and a 1uF ceramic in parallel between power and ground close to the amp.

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mrhume
 
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Re: I can hear my gemma on my Audio FX.

Post by mrhume »

Hi Franklin,
thanks for the reply. I understand they must be wired parallel, but I'm just not really clear on how one does that. I get that you attach the positive lead on the capacitor to the positive wire, and the negative to the negative, but how are you meant to attach them? Like do you feed the leads from the two capacitors through the holes in the Audio FX board along with the power wires? Or do you somehow splice them in to the wire itself before it reaches the board? Or do you have to get a breadboard or something and attach them with that?

As I said, I'm a complete and utter beginner, so please excuse the extremely basic questions! If there is a reference for the right way to wire this, I would be very grateful for a link.

Thanks again,
Josh

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adafruit_support_bill
 
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Re: I can hear my gemma on my Audio FX.

Post by adafruit_support_bill »

For experimenting and prototyping, a breadboard is the easiest solution. On most breadboards, there is a power bus along the side of the board. You can plug your power wires in there as well as both capacitors. https://www.adafruit.com/products/64

Once you have a circuit that performs to your expectations, you can make it permanent by transferring it to something like a perma-proto board. That has the same layout, but you can solder the connections to make them permanent. https://www.adafruit.com/products/1609

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