# Distorted Sound from Cowlacious Scary Terry Board? Need help!



## Death Wraith (Mar 23, 2006)

Something is going wrong with my main prop. I'm using a Prop-1 to drive a servo for head turning. I have a PIR set thru the Prop-1 to trigger the newest version of the Scary Terry Servo board from Cowlacious. All that works fine. But when the audio is triggered it comes out very distorted. I'm using the better quality 60 second chip and the chip sounds fine when played back on the Cowlacious chipcorder board after I record it. I know it's not the sound file being recorded too loud. There is also additional audio interference when the mouth servo is active through the ST board. Something somewhere has gone wrong, maybe some type of filter on the ST board?

Not much time left. Can anyone help??

DW


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## Otaku (Dec 3, 2004)

Do you have any 110 volt lines near the Cow board? May be 60 cycle interference. Try wrapping the Cow board loosely in aluminum foil to shield it. Does this distortion occur if the servos are not active, and could anything be interfering with the speakers?


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## Death Wraith (Mar 23, 2006)

I'm checking my setup with headphones so no interference there. There is no sound interference from the head-turning servo which is running off the prop-1. I did have a power strip mounted right next to the boards and moved it, but no improvement. I tried a loose covering of foil over the top of the board and no change. There is also an infrequent popping sound through the headphones (every 2 or 3 seconds) that I never noticed before.

Thanks for the advice Otaku. You're always the man when it comes to electronics! Tomorrow I'm gonna try a set of speakers and also plugging the two boards into seperate outlets instead of one powerstrip.

Any other ideas?

DW


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## Otaku (Dec 3, 2004)

You have both the sound board and the servo driver board as separate units? Are you using wall warts to power them, or battery packs? Try isolating at least one of them with a 6 volt AA pack and see if that changes anything. That popping sound you mentioned sounds familiar, too. I've had that issue before, and was only able to get rid of it by powering down the chip, erasing the file and reloading it. Don't know if it's related to the distortion problem, though.


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## Death Wraith (Mar 23, 2006)

Not separate boards, just running the Scary Terry board with the onboard 60 sec chip. The popping sounds comes through even when the sound file isn't playing. Using walwarts for power so I'll try hooking up a battery pack. I'm also using an extension cable on the mouth servo and I'm wondering if there might not be a problem with that.

Everything is mounted on a board inside the prop so I'm going to undo everything and reset it on my table to test it out.

I got an email back from Carl at Cowlacious and he didn't have a clue as to what could be wrong.

DW


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## Death Wraith (Mar 23, 2006)

The popping noise is definitely caused by the servo. Unplugging the servo eliminates the popping. I tried 4 different Hitec servos and they all did the same thing distorting the sound when they move.

The overall distortion of the sound file (even without the servo attached) is still a mystery. Maybe dirty contacts?

DW


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## gmacted (Jan 18, 2006)

The problems you are seeing may be caused by a "ground" issue. Since you are using two different "wall-warts", but are connecting the two boards together, you need to have a common ground point. Do you have the "GND" pin from the Prop-1 connected to the GND point on the Scary Terry board? I'm not familiar with the Scary Terry board, so I'm not sure where you would tie it, but that may be causing your problem.


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## Death Wraith (Mar 23, 2006)

Yes I have a common ground running from the Prop-1 'GND' pin over to the ST board. I did discover that the distortion was because I was using headphones! I hooked up a pair of powered speakers and the audio sounds fine. Maybe different impedence made the headphones distort with this board? There is still a very low, very fast 'popping' whenever the mouth servo moves, but on the powered speakers it is a lot softer and really something I can live with.

Thanks for all the help guys!

DW


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## DeathTouch (Sep 6, 2005)

Have you tried using a battery as a source.


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## Sickie Ickie (Jun 20, 2006)

I hear that you can use a potato as a battery.


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