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Unread 12-20-2008, 05:07 PM
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I think one of my Jaguars ate a chipmunk.

Once we got our test bot up and driving with the new control system, we noticed something odd.

One of our Jaguars (and only 1) makes a very interesting high pitched squeal. This occurs with the fan on or off, with the system enabled or disabled. We've checked the wiring, removed the PWM, and it continues. The pitch changes slightly when the LED blinks.

Did our Jaguar swallow a chipmunk, or is something else going on?
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Unread 12-20-2008, 06:34 PM
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Re: I think one of my Jaguars ate a chipmunk.

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Originally Posted by Tom Line View Post

Did our Jaguar swallow a chipmunk, or is something else going on?
Maybe that's what my Jaguar did before it gave up the ghost. I sent it back to Luminary for an autopsy. Have you checked the output? Is it still linear? Keep us apprised of the ultimate fate of yours; I will do the same.
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Unread 12-20-2008, 06:51 PM
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Re: I think one of my Jaguars ate a chipmunk.

Sure thing!

That's the other part of this that's a bit odd - that particular Jag is NOT one we have put any load through at all - we are only running two sims because we rebuilt our 2006, 2007, and 2008 robots this fall. So we are only using two of the Jags, and those two are whisper silent.
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Unread 12-21-2008, 03:12 PM
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Re: I think one of my Jaguars ate a chipmunk.

Are you positive it is the Jag squealing, and not the PD? We ran out of chipmunks while building the PDs, and had to resort to squirrels, groundhogs and ferrets.

I find it really hard to localize high pitched noises, and the PD is known to squeal.
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Unread 12-21-2008, 05:15 PM
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Re: I think one of my Jaguars ate a chipmunk.

So what makes the PD squeal? We noticed it yesterday during the benchtest. Seems like when the Jag lights stopped blinking, the PD would "squeal". Actually sounded more like the hamster wheel than a chipmunk.
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Unread 12-21-2008, 05:20 PM
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Re: I think one of my Jaguars ate a chipmunk.

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Originally Posted by rsisk View Post
So what makes the PD squeal? We noticed it yesterday during the benchtest. Seems like when the Jag lights stopped blinking, the PD would "squeal". Actually sounded more like the hamster wheel than a chipmunk.
I believe the noise from the PD is related to the voltage regulators for the 24v(cRio), 5v(Camera), and 12v(WiFi) regulated outputs, but I'm not an electrical engineer so I'm probably wrong.
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Unread 12-21-2008, 08:23 PM
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Re: I think one of my Jaguars ate a chipmunk.

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Originally Posted by rsisk View Post
So what makes the PD squeal? We noticed it yesterday during the benchtest. Seems like when the Jag lights stopped blinking, the PD would "squeal". Actually sounded more like the hamster wheel than a chipmunk.
The source of the PD squeal is the 12V (and sometimes 24V) boost supplies. Nominally, the boost supply runs at ~600kHz - way out of the audible range. What you are hearing is somewhere in the 20kHz region(ish).

The boost circuit (inductor specifically) was sized to be able to handle the maximum stress conditions. Since it has a fixed frequency and a minimum on time, there is a minimum amount of work it can do in any given cycle. If it is asked to do less, it will simply go to sleep for a few cycles before trying again. This napping or "pulse skipping" happens in the audible range.

Obnoxious? Yes.
Bad? No.
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Unread 12-21-2008, 09:45 PM
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Re: I think one of my Jaguars ate a chipmunk.

Quote:
Originally Posted by EricVanWyk View Post
The source of the PD squeal is the 12V (and sometimes 24V) boost supplies. Nominally, the boost supply runs at ~600kHz - way out of the audible range. What you are hearing is somewhere in the 20kHz region(ish).

The boost circuit (inductor specifically) was sized to be able to handle the maximum stress conditions. Since it has a fixed frequency and a minimum on time, there is a minimum amount of work it can do in any given cycle. If it is asked to do less, it will simply go to sleep for a few cycles before trying again. This napping or "pulse skipping" happens in the audible range.

Obnoxious? Yes.
Bad? No.
Thanks for the details.
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