Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default Ping Jim Wilkins: Audio filter

On Saturday, April 8, 2017 at 8:25:35 PM UTC-4, Clare wrote:
On Sat, 8 Apr 2017 14:00:31 -0700 (PDT), wrote:

On Saturday, April 8, 2017 at 4:48:35 PM UTC-4, Jim Wilkins wrote:
wrote in message
...
On Saturday, April 8, 2017 at 2:59:13 PM UTC-4,
wrote:
On Saturday, April 8, 2017 at 2:00:06 PM UTC-4, Jim Wilkins wrote:
"Tim Wescott" wrote in message
...
On Fri, 07 Apr 2017 08:51:21 -0700, edhuntress2 wrote:

Yo Jim -- and anyone else who may be interested.
.............

Should be able to do the signal processing digitally, so the
hard
part
will be making a user interface that allows the pro users to
get the
most
out of it while making it easy enough for the ordinary guy so
it
doesn't
just get thrown through the wall.

--
Tim Wescott

I can't claim that I'm good at it but I have a lot of experience
designing user interfaces and writing the instruction manuals.

I'm experimenting with a homebrew grid / solar powered battery
charger
that can be set to run unattended or used manually to diagnose
and
restore neglected Lithium, NiCad and Lead-acid batteries. Earlier
this
week it recovered solder-tabbed Li-ion 18650s from "dead" cell
phone
boosters, this morning it brought back a fully discharged DeWalt
NiCad
pack enough for the automatic charger to accept it, and now it's
working on an AGM that went bad in storage. The once useless
battery
delivers 60A.

It's a simple circuit, the hard part is knowing how to use it,
and I
don't have all the answers yet.

Maybe the reason they aren't on the market already is that they
can as
easily destroy a battery as save it.
-jsw

Speaking of Li-ion, Metabo claims that their new 36 V cordless tool
battery pack can deliver 2,500 Watts, as used in their new 9-in.
angle-head grinder.

Maybe my arithmetic is off, but that says roughly 70 A to me. The
battery pack looks like it's just a standard 10-cell pack. I've
read that the low-end internal resistance for advanced Li-ion cells
is around 0.5 Ohms.

My calculation says the battery pack is dissipating 350 Watts or so
at full load, which sounds unreasonable. This is a normal-size 36 V
battery pack.

What do you think?

--
Ed Huntress

Aha, I think I answered my own question. It appears that internal
resistance of Li-ion cells vary a lot by type, and the cells used in
power tools can be as low as 18 milliohms.

That gives a more reasonable result.

--
Ed Huntress

The little DC Volt/Amp/Watt meters sold to RC hobbyists for their
Lithium packs read over 100A. The cheap tabbed 18650s I'm salvaging
from cell phone portable chargers measure around 75 milliOhms full,
150 nearly discharged.
http://www.ebay.com/itm/like/3317138...&ul_noapp=true

-jsw


Still, it's amazing that those smallish 6.2 Ah Metabo packs will deliver almost 70 A. That seems extremely high, but I guess that's where the technology is now.

How about the pocket sized (well, big pockets) lithium booster packs
that will provide 600 amps of cranking power??


That, too, is pretty amazing. But cranking for a few seconds isn't going to generate the quantity of heat you get from running a grinder for a few minutes.

All in all, it's pretty staggering performance, both ways.

--
Ed Huntress

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Default Ping Jim Wilkins: Audio filter

On Sat, 08 Apr 2017 15:06:40 -0700, Gunner Asch
wrote:

On Fri, 7 Apr 2017 13:01:13 -0400, "Jim Wilkins"
wrote:

wrote in message
...
Yo Jim -- and anyone else who may be interested.

I spend an hour last night tracking down some noises in my furnace
blower, using my usual piece of aquarium hose stuck in my ear g, and
I wondered if there might be a market for an advanced kind of
mechanic's stethoscope -- something that ought to be a piece of cake
for someone like you.

Maybe something like this is on the market. If so, forget it. If not,
consider this:

I had two noises, from different sources, and the interference between
them made it all but impossible to find the origins of the noises. One
was some mechanical interference between the centrifugal fan and its
housing, at one end of the armature shaft; the other was vibration
resulting from stickiness in the centrifugal throw-out switch (a
fail-safe switch that prevents the gas valve from opening), at the
other end of the shaft. I finally took the whole thing apart and found
both problems, but it wasn't easy to find them when the motor wasn't
running.

So, I wondered about the idea of making a small, cheap,
battery-powered amplifier, with a mike and a headphone jack, that
contained a couple of active, adjustable audio filters, one high-pass
and another low-pass. Made a notching filter or bandpass filter to
make it slick.

I don't play with engines much these days, but I can recall times when
such a device would have made quick work of tracking down engine
noises.

There it is. If you make it and sell it, the idea is yours. Watch out
for patents.



http://www.harborfreight.com/mechani...ope-69913.html


Long screwdrivers seem to get used more often than my stethoscope.

--
Newman's First Law:
It is useless to put on your brakes when you're upside down.
--Paul Newman
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Default Ping Jim Wilkins: Audio filter

On 8 Apr 2017 00:18:53 GMT, "DoN. Nichols"
wrote:


So, I wondered about the idea of making a small, cheap,
battery-powered amplifier, with a mike and a headphone jack, that
contained a couple of active, adjustable audio filters, one high-pass
and another low-pass. Made a notching filter or bandpass filter to make
it slick.


Instead of a microphone, use an old phono cartridge with a brass
whisker where the needle normally was held. (Ceramic or Crystal
cartridge -- not the fancier stereo cartridges of higher quality and
lower stylus force which came later.) Astatic was the brand of one of
these types. I wonder if you can still find them on eBay?


I did essentially the same thing except that I used the active element
out of a cheap set of headphones. In this design, the speaker "cone
is a somewhat corrugated piece of clear plastic with about a 3/4"
diameter "voice coil" and a super magnet. The other pole piece is a
cylindrical piece that almost touches the cone.

I went this route because I found phono cartridges much too fragile. I
cement the rod to the center of the cone with strong but resilient
(E6000) cement. If I push too hard, the cone moves until it touches
the center pole piece and no damage is done. In fact that forms a
mechanical high pass filter which is usually needed.

In the electronics box was an amplifier, a low pass filter, a high
pass filter and a bandpass filter with adjustable width.

I used the unit mostly for charging AC systems where I didn't have a
refrigerant weight to go by. As I described previously I listen to
the refrigerant flow. The band pass filter was invaluable. It
chopped all the low frequency noises such as the compressor
compressing, the engine running and so on. It also chopped the high
frequency of the refrigerant flowing through the rest of the system.

A notch filter would have been handy, though I emulated one pretty
well by drawing the high and low pass filters close together.
Especially handy for listening for ball bearings that have a bad ball
but aren't making noise yet. one can notch out the regular beat of
the balls rolling and hear just the clunk of the one ball with a flat
spot go by.

When I get time I am going to re-implement this as a learning DSP
project. This time with a display capable of showing an FFT so that I
know where to put the band pass filter or maybe have it auto-find the
peak of interest.

This an ultrasonic listener are two of the more useful tools a modern
mechanic can have.

It sounds interesting -- and more so if you can do stereo
pickups with old phono cartridges. :-)


I didn't find stereo all that useful. The probe is extremely
directional off the end, sensitive to longitudinal motions of the
probe. One simply changes the angle of the probe to go looking for
the noise source.

John
John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address

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Default Ping Jim Wilkins: Audio filter

On Sat, 08 Apr 2017 17:02:02 -0500, Tim Wescott
wrote:


That's a bit over 11C, which is well within the limits that model
airplane battery packs are run these days. Every day packs come out that
can handle more current for the capacity -- it's probably tools like that
which are driving it.


That, EVs and grid level energy storage.

I have a friend who is one of the top guns in EV drag racing. His
rail dragster isn't all that much slower than Top Fuel.

I have in my hands one of the batteries he developed in conjunction
with a chinese battery company. It's a bit smaller than a garden
tractor battery, 48 volts and 14 amp-hours. The real kicker is that
it is capable of supplying 1000 amps while keeping the voltage above
46 volts and do so until the charge is depleted (defined as 20%).

I'm working on a product that will use 2 of a lower capacity version
of that battery (96 volts, 7 amp-hours). I have to say that I work
with that little bomb with great trepidation.

John

John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address

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Default Ping Jim Wilkins: Audio filter

On Sat, 08 Apr 2017 21:26:25 -0700, Larry Jaques
wrote:

On Sat, 08 Apr 2017 15:06:40 -0700, Gunner Asch
wrote:

On Fri, 7 Apr 2017 13:01:13 -0400, "Jim Wilkins"
wrote:

wrote in message
...
Yo Jim -- and anyone else who may be interested.

I spend an hour last night tracking down some noises in my furnace
blower, using my usual piece of aquarium hose stuck in my ear g, and
I wondered if there might be a market for an advanced kind of
mechanic's stethoscope -- something that ought to be a piece of cake
for someone like you.

Maybe something like this is on the market. If so, forget it. If not,
consider this:

I had two noises, from different sources, and the interference between
them made it all but impossible to find the origins of the noises. One
was some mechanical interference between the centrifugal fan and its
housing, at one end of the armature shaft; the other was vibration
resulting from stickiness in the centrifugal throw-out switch (a
fail-safe switch that prevents the gas valve from opening), at the
other end of the shaft. I finally took the whole thing apart and found
both problems, but it wasn't easy to find them when the motor wasn't
running.

So, I wondered about the idea of making a small, cheap,
battery-powered amplifier, with a mike and a headphone jack, that
contained a couple of active, adjustable audio filters, one high-pass
and another low-pass. Made a notching filter or bandpass filter to
make it slick.

I don't play with engines much these days, but I can recall times when
such a device would have made quick work of tracking down engine
noises.

There it is. If you make it and sell it, the idea is yours. Watch out
for patents.



http://www.harborfreight.com/mechani...ope-69913.html


Long screwdrivers seem to get used more often than my stethoscope.


Ayup. I keep a 18" long Klein phillips screwdriver in my Platt tool
case that gets nearly all this sort of duty.

Gunner

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