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Noise when powered by 9v battery

8 years 3 months ago - 8 years 3 months ago #411 by curado
Noise when powered by 9v battery was created by curado
Looking for suggestions. The Pedalshield seems to work fine when powered by USB, but powering with 9v battery causes a very audible background frequency.

9 out of 10 times when powered on with the 9v battery, you get the background noise. But sometimes it's quiet -- it's just a question of chance. When powered by USB, you get a fairly clean signal. Is this some sort of weird grounding issue?

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8 years 3 months ago #412 by Ray
Replied by Ray on topic Noise when powered by 9v battery
Hi,

Its the first time I hear about this problem when using a 9V battery.

So I guess that you use a clip adapter an power everything using the black connector on the Arduino board, right?



Could you also check that the polarity is the right?
Could you check that you have all the right voltages at the test points? +5V, -5V, etc..
Could you check that the battery is charged?
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8 years 3 months ago #413 by curado
Replied by curado on topic Noise when powered by 9v battery
No eBay APP ID and/or Cert ID defined in Kunena configurationGood idea -- I will check the test points.

It does power on and play properly even with the high pitch frequency in the background. I am using the VIN pin because the PedalShield is mounted inside of the guitar body. I have read that using the VIN pin is a bad idea and will later revise to use the barrel plug pins (for the diode protection in particular).

Tried it with a fresh, fully charged alkaline battery and with a lithium rechargeable 9v. Seems to occur either way.

The Arduino DUE is from eBay:

Is SainSmart OK?

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8 years 3 months ago #414 by Ray
Replied by Ray on topic Noise when powered by 9v battery

The Arduino DUE is from eBay:
Is SainSmart OK?

Some folks reported that some eBay boards are not as good as the Arduinos, but on eBay the DUEs shouldn't be necessary bad.

I have used a barrel plug in the past and it works fine, I dont have any clear idea of why do you get this issue when applying power like that.

The best idea is to check that you have all the test points with the right voltages.

Are you sure that you are applying the voltage in the right polarity? pedalSHIELD is pretty tough and it will work even in the most difficult situations, sometimes I did something wrong myself and I am impressed that it can produce sounds...

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8 years 3 months ago - 8 years 3 months ago #415 by curado
Replied by curado on topic Noise when powered by 9v battery
Added a separate 5v regulator connected to the 5V pin on the DUE. The noise is completely gone. Unfortunately when powered by USB, the power backfeeds into the regulator. This is problematic at best -- very sketchy. But it's not necessary to plug into USB very often.

I'm thinking it's simply a problem with the voltage regulator in this particular DUE.

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8 years 3 months ago #418 by Ray
Replied by Ray on topic Noise when powered by 9v battery
In my experience, the voltage regulators on the DUEs are pretty noisy, if you are able to reduce it using an external linear regulator its a good solution, the USB power is usually very noisy as well....
Thanks for your input!

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6 years 10 months ago #881 by test123
Replied by test123 on topic Noise when powered by 9v battery
I wonder if a single 9V is enough to power the due + pedalshield without causing the switching psu to sag more deeply into it's ripples, baring it's 500khz switching freq.

I've spend most of the morning tracking down the noise issues Regular USB adapters seem to be out as well for noise. Some do ok (200-400mv peak to peak), but some (like my laptop) introduce a high pitched squeal.

Looking at the due schematic, it doesn't even try to regulate the 5v outside of a couple of ferrite beads. It doesn't have sufficient noise reduction caps on the board as well.

The best I've been able to do so far is 6AA batteries (which gives me 100-200mv peak to peak when writing zeros to the DACs). I'll try putting together a 7805 circuit and going straight to the 5v in pins - looks safe enough on the schematic (as long as I don't reverse the pins :)), that's basically what the higher voltage switcher is doing from the USB's point of view.
The following user(s) said Thank You: Ray

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6 years 10 months ago - 6 years 10 months ago #883 by Ray
Replied by Ray on topic Noise when powered by 9v battery
Thanks for your investigation!

It doesn't have sufficient noise reduction caps on the board as well.

There are two caps c15 and c16 if I remember well, placed next to the tc1044 (they are omitted in the schematic, check the pcb) , that give extra decoupling to +5v and -5v.

I tried different values decaupling +5 and - 5v but I did not find much difference, the game changer is the powe supply, in my case an apple usb power adapter is the best so far, but im sure that there are plenty of alternatives out there.

Let us know your progress!!

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6 years 10 months ago - 6 years 10 months ago #886 by test123
Replied by test123 on topic Noise when powered by 9v battery

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