measuring/detecting/reducing chip noise?

[Mykle James Hansen]

Hi all,

I’ve been trying to figure out a way to reduce background noise
on the Pocket Integrator (PI). It appears that the Pocket Operator (PO)
parent board is dumping some noise into the power connection
between the two boards. But I’m having a hard time characterizing that noise.
Any advice would be much appreciated.

(I have some capacitors in place to try to filter out that
noise at the interconnection point — 10f electrolytic & 1f ceramic
— but there’s still something there. If I can’t characterize
it, I’m probably not filtering it right.)

On the one hand, using my scope on the output ports,
I see a pretty constant ringing at some supersonic frequency,
whenever the PI is drawing power from, or providing it to, the PO.
The freq counter on my scope does not seem to be
locking on for some reason, but it seems stable & I wouldn’t be
surprised if it was the 40hmz clock of the Pocket Operator
I was seeing there.

On the other hand, when I connect the output ports to
my mixer and listen on my speakers, I hear a 733hz tone.
Some audio software I have puts it at about -60db ,
which is quiet but still clearly audible if I turn
the levels way up. It sounds a lot like noise I’ve
heard in the noise floor of digital devices before.
But I don’t see it on the scope, that’s the weird thing.

I also can hear a second, higher pitched tone when I press
certain buttons on the KO. But I don’t see any changes
at all on the scope when I do that, which seems really
strange. This could simply be some loop inside the
PO’s MCU that repeats at an audible frequency … but
why isn’t it visible on the scope? Is that normal?

I’m wondering if the supersonic noise I’m seeing on the
scope is the cause of the audible noise I’m hearing on the
output, like a subharmonic or something? It’s just very
strange that I don’t see any change on the scope at all when
the audible tones change pitch.

Yrs in a fit of puzzlement,
-mykle-

[Nathan McCorkle]

Your sound mixer likely has a much lower impedance than the scope probe and input. Resistance or impedance is an important component of noise filters. So your analysis setups are not apples to apples, thus I'm not surprised that your observations are different. Have you tried using the frequency detected with the scope as input in some filter equations? LC seems appropriate for a power line, but maybe if your power draw is low enough you could consider a low value R for an RC filter too.

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[Jim bell]

There are apparently a large number of economical laser range finders available these days, from companies with odd names like Mileseey, Aicevoos, and others.  They are typically at prices from about $20 to $40 although more expensive models with cameras are available as well.

They are available in a series of ranges, commonly 50, 70, 100, 120 meters.  Presumably they work on the basis of time of flight, and they quote a resolution and presumably accuracy of around 2 millimeters.

And, of course, they are probably rated based on the reflection of the laser from a non-cooperative Target, paint, wood, vegetation, etc.  I think it's actually surprising that they do as well as they do with such targets.  

But there exists far more cooperative targets, such as plastic molded retro reflectors, otherwise known as a corner cube.  I wonder how much improvement in range could occur with using such cooperative targets.

The main limitation I see is that some of these devices seem to be limited in the number of digits that they can display. But if the device is rated for 120 m, what will it display if the cooperative Target is 199 M away?  Or, if the target is 201 meters away?

On Wed, Dec 27, 2023, 5:09 PM Mykle James Hansen <my...@mykle.com> wrote: