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Is MintyBoost too "noisy" for this
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Please be positive and constructive with your questions and comments.

Is MintyBoost too "noisy" for this

by es2mac on Thu Nov 04, 2010 5:05 am

Here's something I'm really puzzled with --

I'm working on a project where I have a Teensy reading analog inputs from 4 linear pots (a ThinPot, thinner version of the SoftPot), then use the readings to set up timer interrupt to toggle two pins to play notes on a little speaker.

When Teensy is connected to the computer it does just fine. When I use a MintyBoost to power it however, I found that it generates a constant static. It does still play the tone I want it to play though somewhat poorly.

I played with increasing delays and raising minimum analog readings required to turn on speaker, and it seems to be that the problem is the analog reading having a lot of "jitter" when connected to the MintyBoost. In particular analog pin doesn't read zero when I thought it would.

So by playing with delay and a cutoff value I can do away with the static at no input, and regular sound plays somewhat normally but the pitch still jumps around; with fast refresh rate it sounds like the speaker is "popping."

I wonder if this is because the MintyBoost's output is too "noisy?" Is there a way to get around it?
es2mac
 
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Joined: Wed Mar 31, 2010 1:08 am

Re: Is MintyBoost too "noisy" for this

by stinkbutt on Thu Nov 04, 2010 5:31 pm

If you believe that the Minty Boost as a power source is "noisy" then there's a simple solution: Throw a noise filtering capacitor in between Vcc and Ground to filter out the noise. If you're still seeing "pops" and whatever else, then it's probably not power supply noise. Minty Boost isn't, to my knowlege, intended to power other circuits, but just charge an iXXXX.
Red M&M, Blue M&M: They all wind up the same color

stinkbutt
 
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Re: Is MintyBoost too "noisy" for this

by len17 on Thu Nov 04, 2010 10:06 pm

It might not be the output that's noisy, it might be RF interference from the minty boost converter.

Try this: Power the Teensy from the computer, and connect the MintyBoost to another device (iPod or whatever). Put the MintyBoost close to the Teensy. Does it cause problems?

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Re: Is MintyBoost too "noisy" for this

by es2mac on Fri Nov 05, 2010 12:23 pm

Nice idea, didn't think of that one. Tried it out just now, with Teensy connected to the computer and MintyBoost charging an iPod Touch. No effect on Teensy though, even if I lift the MB's lid and wave things close together.
es2mac
 
Posts: 2
Joined: Wed Mar 31, 2010 1:08 am

Please be positive and constructive with your questions and comments.


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