Waveshield : buzz with batteries

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alwentio
 
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Waveshield : buzz with batteries

Post by alwentio »

Hi,

I want to attach a PIR sensor to an arduino with a waveshield connected to small amplifier, 12V-0.5A.
Everything works fine but the amp is buzzing when the waveshield is playing.

This happens with one 12V battery connected to the amp+arduino. No buzz when the waveshield is not playing.
When I use 2 separate batteries, no buzz.

It looks like the current needed by the amplifier when it's playing is doing some extra noise in the arduino's power and create the buzz.

So my question is how can I isolate the power between the arduino and the amplifier ? Condenser ?

Thank you very much for any help.

David.

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adafruit_support_mike
 
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Re: Waveshield : buzz with batteries

Post by adafruit_support_mike »

alwentio wrote:It looks like the current needed by the amplifier when it's playing is doing some extra noise in the arduino's power and create the buzz.
That's possible. An amplifier's job is to throw a lot of power around, and that can create noise for other systems connected to the same supply.
alwentio wrote:So my question is how can I isolate the power between the arduino and the amplifier ? Condenser ?
For starters, try moving the Arduino out of the amplifier's power loop. Even if you're using the same battery, have one set of wires going from the battery to the amp, another set going from the battery to the Arduino. The battery terminals should be the only place where the two circuits meet. Having both 'quiet' and 'noisy' devices connected to the same wire can cause trouble.

For additional protection, put a couple of capacitors on the Arduino side of the battery.. 1 microfarad and .1 microfarad are the usual values. The .1u capacitor damps out fast signals trying to come through the power line, and the 1u capacitor handles slower ones.

The step after that is to put a voltage regulator between the battery and the Arduino (probably about a 9v regulator), but by then things are getting complicated enough that it's probably easier to use separate batteries for the Arduino and the amplifier.

alwentio
 
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Joined: Tue Oct 09, 2012 12:51 pm

Re: Waveshield : buzz with batteries

Post by alwentio »

Thank you very much for your reply.

So I tested the two capacitors between Vin and ground of the arduino.
No changes.
I also tried, following another advice, to put a 6 ohm resistor between +12V then a 1000µF 23V between Vin and ground, no changes either.
Still the same buzz when playing.

I don't know how to "decouplate" powers, so I think I'll have to go for two different batteries.

If anyone has more luck with that, I'd be interested.

Thanks again.

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JMB1971
 
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Re: Waveshield : buzz with batteries

Post by JMB1971 »

Hi,

I seem to be having exactly the same issues with my waveshield sound as listed here. I am new to the digital electronics world so all the advice went straight over my head so could I ask for some advice with my particular setup?

My project is a gameshow sound effects console ( I am a teacher looking to bring more interactivity to my lessons). I have a waveshield playing sound bites from 7 interactive buttons. I have the waveshield attached to a velleman amplifier kit (K4001 - 7w mono amplifier). This, in turn, is attached to a 4 Inch Coaxial With Piezo 4 Ohm 20w speaker all running from a single 9.6v 1A Nicad battery. I have no clue if they are even remotely compatible, the amplifier was chosen as it was in kit form so I could practice my soldering, the speaker as it was 4 ohm and the battery; nicked from my RC car.

I linked these together using the instructions from velleman and waveshield tutorial though I kept the original pot on the waveshield; cue lots of buzzing. I then used a separate battery and buzzing stopped though there was no volume control and it was permanently full volume. I connected a separate 10k pot with the separate battery and hey presto, no buzzing, perfect sound (as far as 12 bit uncompressed PCM mono sound can be!).

So, long story short, I now know the problem is the noise generated from running everything from a single 9.6v battery. However, my console is already packed to the gunnells and I have next to no space for a second battery. I would like to try and keep the single battery (though I recognise that I may need to upgrade to a 12v battery).

I forgot to mention, I am running power through a nicad charging circuit. Ideally, I would like to simply add to this circuit when isolating the power between the arduino and the amplifier to solve my problem if possible.
Nicad Charger PCB.png
Nicad Charger PCB.png (257.69 KiB) Viewed 306 times
So, my questions;

1. How can I change the circuit to effectively isolate the power between the arduino and the amplifier?

2. Is this feasible (read easy)?

3. Are there easier and more simplified ways of solving this issue?

4. If I have to go down the route of attaching caps and rectifiers etc, could someone draw me a diagram?



Any suggestions would be greatly appreciated! v I have a month to get this project finished in time for September!

JmB1971

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adafruit_support_bill
 
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Re: Waveshield : buzz with batteries

Post by adafruit_support_bill »

I'd start with Mike's suggestions above:
have one set of wires going from the battery to the amp, another set going from the battery to the Arduino.
Separate wiring helps to isolate the wave shield from power fluctuations in the amplifier.
For additional protection, put a couple of capacitors on the Arduino side of the battery.. 1 microfarad and .1 microfarad are the usual values.
These will help filter out any noise that does manage to find its way into the power lines.

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JMB1971
 
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Re: Waveshield : buzz with batteries

Post by JMB1971 »

Hi Bill,

Thanks for your reply, unfortunately, as I stated earlier, Mike's advice was over my head. I did add a terminal block to nicad charger and ran a connection from the battery but no change;
Wiring.png
Wiring.png (285.56 KiB) Viewed 295 times
It is likely that I have incorrectly wired it up to the nicad charger but no ideas how else to do it?

JmB1971

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adafruit_support_bill
 
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Re: Waveshield : buzz with batteries

Post by adafruit_support_bill »

If you are trying to diagnose the noise problem, you should simplify your circuit. Try it without the charger.

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