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'Bouncing Ball Detector'
1998\07\09@140754 by Rock Thompson

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In an effort to further the athleticism of my children, so they can
someday be filthy rich and support their kindly old father, I am
building a wooden target for them to throw a ball at.

I want to count the number of times the ball hits the target.  A PIC
will count the number of hits and handle an LED display.  But I'm
hoping for suggestions on how to detect the hits.  Two things come to
mind: An accelerometer responding to the vibration of a hit, or a
microphone that picks up the sound of a hit.

Any further ideas or comments?

Thanks, Rock




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1998\07\09@144125 by Timothy D. Gray

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face
A simple robot impact sensor would do...
--------------+------- +vcc
*            *
--------------+------- TO PIC
Two pieces of metal with insulators at the end... one wire on each plate..
voila! vary the thickness and size of the plates to adjust sensitivity.

On Thu, 9 Jul 1998, Rock Thompson wrote:

{Quote hidden}

1998\07\09@153426 by Andy Kunz

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face
>mind: An accelerometer responding to the vibration of a hit, or a
>microphone that picks up the sound of a hit.

The mike is easier.  Hook it up to a low-pass filter to detect the sudden
but sustained noise of a hit, vs. background noise of kids playing.

Andy


==================================================================
Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
==================================================================

1998\07\09@153519 by David Anderson

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face
Or you could use a simple microphone with an analog comparator. Check around
in the web pages for analog synthesizers about using piezo speakers as
triggers. You also wouldn't have to debounce the input as you would with the
scheme shown below.

{Original Message removed}

1998\07\09@164156 by Eric Belanger

picon face
Why not try a PIEZO Electric disc. Its innexpensive and verry sensitive
if you mount it firmly on the surface. You can salvage the disk from a
commercial pizzo buzzer ( The large the better ) or buy just the plain
disk ( available from some distributor ).Take a look ay Shyogo Web
site(http://www.shogyo.com/), the have a huge variety of piezo.

  Eric

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1998\07\09@165928 by Reginald Neale

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>In an effort to further the athleticism of my children, so they can
>someday be filthy rich and support their kindly old father, I am
>building a wooden target for them to throw a ball at.
>
>I want to count the number of times the ball hits the target.  A PIC
>will count the number of hits and handle an LED display.  But I'm
>hoping for suggestions on how to detect the hits.  Two things come to
>mind: An accelerometer responding to the vibration of a hit, or a
>microphone that picks up the sound of a hit.
>
>Any further ideas or comments?
>
>Thanks, Rock
>
Interesting problem. Childrens' toys are among the most difficult devices
to make idiot-proof. How do you defend against the trivial case where the
child just walks up and whacks the target to increase the score? Probably
YOUR kids would never do such a thing :-)

Reg Neale

1998\07\09@180458 by ephen Rothlisberger

picon face
>In an effort to further the athleticism of my children, so they can
>someday be filthy rich and support their kindly old father, I am
>building a wooden target for them to throw a ball at.
>
>I want to count the number of times the ball hits the target.  A PIC
>will count the number of hits and handle an LED display.  But I'm
>hoping for suggestions on how to detect the hits.  Two things come to
>mind: An accelerometer responding to the vibration of a hit, or a
>microphone that picks up the sound of a hit.

A strain gauge connected to an op-amp, and a comparator to give a hit/no
hit indication to the PIC.

Stephen.

1998\07\10@025459 by Morgan Olsson

picon face
At 15:31 1998-07-09 -0400, you wrote:
>>mind: An accelerometer responding to the vibration of a hit, or a
>>microphone that picks up the sound of a hit.
>
>The mike is easier.  Hook it up to a low-pass filter to detect the sudden
>but sustained noise of a hit, vs. background noise of kids playing.
>
>Andy
>
Instead of mike, use a piezoelectric disk and glue it to the backside
surface of the target.

You can get it from a worn out wrist-watch that can beep.


/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  spamBeGonemrtspamBeGonespaminame.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /

1998\07\10@115903 by Peter L. Peres

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On Thu, 9 Jul 1998, Rock Thompson wrote:

> In an effort to further the athleticism of my children, so they can
> someday be filthy rich and support their kindly old father, I am
> building a wooden target for them to throw a ball at.
>
> I want to count the number of times the ball hits the target.  A PIC
> will count the number of hits and handle an LED display.  But I'm
> hoping for suggestions on how to detect the hits.  Two things come to
> mind: An accelerometer responding to the vibration of a hit, or a
> microphone that picks up the sound of a hit.
>
> Any further ideas or comments?
>
> Thanks, Rock

Buy a piezo disc (the kind that is used to make beepers) and glue it to
the wooden target (on the back of it) with a good wood glue, or good
quality contact cement, ceramic face up. The target can be 1/2 inches
thick or so. Then, solder (very gently) a flexible shielded twisted pair
wire to the disc (vinyl player pickup connection wire is great), and start
experimenting. In my experience, this kind of setup gives so much voltage
directly on a CMOS input that I had to use protection diodes and a series
limiting resistor. Some signal conditioning will be required, but a PIC
could do that, and drive the display too.

Peter

1998\07\10@171444 by

flavicon
face
> >>mind: An accelerometer responding to the vibration of a hit, or a
> >>microphone that picks up the sound of a hit.
> >
> >The mike is easier.  Hook it up to a low-pass filter to detect the sudden
> >but sustained noise of a hit, vs. background noise of kids playing.
> >
> >Andy
> >
> Instead of mike, use a piezoelectric disk and glue it to the backside
> surface of the target.
>
> You can get it from a worn out wrist-watch that can beep.
>
You could amplify the output from the transducer, put it through an A/D,
feed it into the fastest PIC you can get, run some nice DSP algorithms to
filter out the exact sound the ball makes and feed the results into a lower
powered slave PIC that does the scoring.

Or you could use a microswitch. :)

Sorry for being such a killjoy, but for such a simple application do you
really need to go to these lengths?

Mike Rigby-Jones
TakeThisOuTmrjonesEraseMEspamspam_OUTnortel.co.uk

1998\07\10@235346 by Timothy D. Gray

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face
>
> Or you could use a microswitch. :)
>
> Sorry for being such a killjoy, but for such a simple application do you
> really need to go to these lengths?
>
WEll he could measure the particle decay of a small isotope glued to the
impact zone... measuring the dopplar difference in the particles woud give
impact speed.. and probably make the kids glow in the dark too!

1998\07\11@011902 by Bill Cornutt

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face
Radio Shack use to sell a vibration detector in their
line of intrusion detection devices.  It is a simple
switch with a weighted thing that will make or break
when it is moved suddenly.

As we live in a world of instant gradification, why
not have a bell go off when the target is hit.

And of course, the pic could be emulated with a couple
of 555's.

Bill C.    RemoveMEbillspamTakeThisOuTcornutt.com

1998\07\11@043858 by Bill Cornutt

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face
As a low tech solution, suspend the wooden target.  Cut a hole
in the center of the target and hang a cow bell ( find a tipped
cow and remove its bell) in the hole.

Bill C.   billEraseMEspam.....cornutt.com

1998\07\12@043640 by Peter L. Peres

picon face
On Fri, 10 Jul 1998, Rigby-Jones, Michael [PAI01:4837:EXCH] wrote:

> Sorry for being such a killjoy, but for such a simple application do you
> really need to go to these lengths?

Actally, it's these simple things that are the hardest to do right, as
someone else has already pointed out (making toys...).

A piezo disc is not overkill for this, it's just right, especially since I
happen to know this precisely. I also know that its output can be fed
directly to 5-Volt powered CMOS logic, using just a resistor in series
with the sensor, and no filter, but that debouncing is required (actually
holdoff of 1-2 sec after a hit is registered, as the plate vibrates quite
a bit). I had used two CMOS decade counters, BCD->7 seg. display drivers,
and transistor boosters to drive a 2-digit jumbo LED display, a 4093 + RC
monostable, a 100 kohm protection series resistor with the disc, and a 15
meg pull-down at the sensor feed-in to the CMOS. This was to react to
tennis balls (the plate was 1/2 inch compact board, about 60x60 cm,
suspended from 2 ropes across the field, or placed against a stool ;).
There was also a thing that turned the diplay power off if no hits came
for about 2 minutes (a spare section of the 4093 did this), as it ran on
batteries (6 Volts: 4 x D-cells I think you call them), and an industrial
heavy-duty red 'mushroom' reset button for the counter (kids get violent
when they lose) <G>. No power switch. And heavy 10 mm aquarium glass in
front of the jumbo display set in a metal rectangular frame flush in a
bevel in the wood with a rubber gasket, and a second identical frame not
so flush on the back. I wished later that I had chosen anti-reflex glass
as it gleamed in the sun.

Just don't use a thicker plate, or you'll need an amplifier and don't damp
its vibration modes by mounting, and use a shielded short audio cable to
connect the piezo disc ;)

Now, would that be enough detail, or do I have to find the PCB layout
and the schematic and attach them ;) (It would be hard, I did this a long
time ago - so I might have to redraw it).

Peter

1998\07\12@125041 by Timothy D. Gray

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face
No not overkill, but the simple plate switch is 1000 times more durable,
will survive a child whacking the sensor with the bat directly,

{Quote hidden}

1998\07\12@143745 by Peter L. Peres

picon face
On Sun, 12 Jul 1998, Timothy D. Gray wrote:

> No not overkill, but the simple plate switch is 1000 times more durable,
> will survive a child whacking the sensor with the bat directly,

The child will be whacking the wrong side of the compact plate with the
bat, as it's the only one he can get at. Besides, do not underestimate the
resilience of a piece of elastic metal plate coated on the far side (from
the blows) with not less resilient and flexible ceramic material. Your
solution contains *moving parts*, and imho will fail before the piezo disc
will even take any visible or measurable damage, when hit through the
compact plate.

I was also not talking about baseball bats, but about tennis balls and the
odd kick (even Karate-style well-trained kick, but done by a kid). No
damage, except to the battery holder, which spilled its heavy contents
inside the case, so it was reinforced with a more solid lid facing
outwards on the back ;)

Peter

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