Prototype Project - Looking for some help

[[email protected]]

Howdy,
I'm currently working on a project to build an machine that uses
Impact Sensors (Tekscan, Interlink, any other inexpensive suggestions?)

to register the user's force of impact and convert the incoming analog
data into an electronic format for storage and data calculations. The
system will be able to run a number of pre-programmed routines that
control multiple analog outputs (LEDs, Sound Components, Etc) and
output statistical reports of a user's use during their session.

The force sensors would be mounted on a 8" diameter vertical tube
with a elastomer padding covering the sensor(s) for impact absorption
and protection. The system would need to register the force applied
directly by a user and activate an analog device to notify the user
they have reached or exceeded certain limits set by the system.

I'm looking for a small company or an individual in the Northern
LA area that is interested in helping build a prototype of this
machine.

The person needs to be willing to work one-on-one with me through
the prototyping stage. Please don't reply to this message with, "Well
I can build it for you for X thousands of dollars" because frankly, I
don't have that kind of money to spend on this. I can afford to spend
some money on the cost of development, but that would have to be worked

out on a personal basis with someone interested in the project, not
just the money.

If this sounds like a project you're interested in, please feel free to

reply to this post. I will be relocating from NY to LA the first half
of February and I would really like to get this project underway.

Thanks a ton,

- Jace

 

[Stanislaw Flatto]

Howdy,
I'm currently working on a project to build an machine that uses
Impact Sensors (Tekscan, Interlink, any other inexpensive suggestions?)

to register the user's force of impact and convert the incoming analog
data into an electronic format for storage and data calculations. The
system will be able to run a number of pre-programmed routines that
control multiple analog outputs (LEDs, Sound Components, Etc) and
output statistical reports of a user's use during their session.

The force sensors would be mounted on a 8" diameter vertical tube
with a elastomer padding covering the sensor(s) for impact absorption
and protection. The system would need to register the force applied
directly by a user and activate an analog device to notify the user
they have reached or exceeded certain limits set by the system.

I'm looking for a small company or an individual in the Northern
LA area that is interested in helping build a prototype of this
machine.

The person needs to be willing to work one-on-one with me through
the prototyping stage. Please don't reply to this message with, "Well
I can build it for you for X thousands of dollars" because frankly, I
don't have that kind of money to spend on this. I can afford to spend
some money on the cost of development, but that would have to be worked

out on a personal basis with someone interested in the project, not
just the money.

If this sounds like a project you're interested in, please feel free to

reply to this post. I will be relocating from NY to LA the first half
of February and I would really like to get this project underway.

Thanks a ton,

- Jace

From your description you don't measure impact, which is a very
demanding measurement in terms of amplification equipment and the
accuracy required in calibration. You measure force applied, on static
known mass, completely different animal. For this an accellerometer with
peak recording instrumentation will do the job.
Just a notion (from lifetime in test department of aerospace industry).
And NO, am happily retired.

Have fun

Stanislaw

 

[[email protected]]

From your description you don't measure impact, which is a very
demanding measurement in terms of amplification equipment and the
accuracy required in calibration. You measure force applied, on static
known mass, completely different animal. For this an accellerometer with
peak recording instrumentation will do the job.
Just a notion (from lifetime in test department of aerospace industry).
And NO, am happily retired.

Have fun

Stanislaw

Stanislaw,

Thanks for the reply. The machine is stationary though so I don't know
if an accelerometer would work for this application. The sensors I'm
looking to use would be of a variable resistance type so it would
measure impact force unless I'm not understanding what you mean?

Basically I want to identify that there was an impact, and how hard
that impact is. The system will allow for setting a target force so
that if the user hits the machine and the force is less than the set
target, it will either not register the hit, or notify the user that
the hit was insufficient by means of some analog signal being a light
or sound.

The system needs to record the force of the hits so it can create
statistical data and do some other calculations that I would like
produced.

I'm throwing around the idea of creating two systems, one that only has
generic contact sensors and one that uses the variable resistance force
sensors.

- Jace

 

[Stanislaw Flatto]

I'm throwing around the idea of creating two systems, one that only has
generic contact sensors and one that uses the variable resistance force
sensors.

- Jace

"Strain gauges?" would do if:
the 'impact' shock wave moves along the test sample without degradation
and is longer than the strain gauge dimention, the attaching glue
transfers this in true form so NO shock absorbing action takes place.
Otherwise your readings recorded and reality have nothing in common.

If you insist on 'impact' as your measure stick better find someone
experienced in this kind of measurements. And such maybe rare like
chicken teeth.

Good luck

Stanislaw

 

[[email protected]]

"Strain gauges?" would do if:
the 'impact' shock wave moves along the test sample without degradation
and is longer than the strain gauge dimention, the attaching glue
transfers this in true form so NO shock absorbing action takes place.
Otherwise your readings recorded and reality have nothing in common.

If you insist on 'impact' as your measure stick better find someone
experienced in this kind of measurements. And such maybe rare like
chicken teeth.

Good luck

Stanislaw

Stanislaw,

I've been doing some research into Strain Guages and I don't know if it
would work for my application only because according to the description
on Wikipedia, "as the object is deformed, the foil is deformed, causing
it's electrical resistance to change", and the object the user would be
hitting is a 8" diameter steel vertical cylinder. Unless we're
counting micro-deformations, the "object" shouldn't deform. But I
understand the principle, it's the same as the piezoresistive force
sensors just instead of using a chemical pressure sensitive ink, the
strain gauges cause variable resistance based on the shape.

I know this goes against most all electrical engineering ideals, but
this system doesn't have to be super accurate. Even rounding to the
nearest pound or point of a pound of force would be sufficient. Hence
why I said I'm considering not using force sensors at all for one
model. I've contacted Tekscan and described what I needed thoroughly
with them and they said that their product is 100% suited for my
application. The only problem is that I can't afford, personally or as
a per-unit cost, to have a custom run of 10,000 sensors made to my size
requirements and their standard "off the shelf" sensors are the size of
a penny and I need a contact area of roughly 6" tall by 24" wide. They
have some leftover sensors from the company that makes those force
sensing brake pedals so that trailer brakes can be applied in addition
to the truck brakes, but they don't make a habit of selling other
people's leftover custom sensor designs, and those are only 3"x5"
anyway.

Basically it comes down to cost versus accuracy. I need to keep the
per-unit cost of my system down under the $1k range to make it
affordable for my prospective clients but I want to give them the best
experience for their buck. For what I'm doing, there are other
products on the market, but in my opinion, they don't fulfill the needs
of their (our) target market.

And just as additional info to take into consideration for the cost
projection, I need either 15 6"x24" sensors or 45 6"x8" sensors to
complete each unit. Using Tekscan's estimate of about $25 per sensor
(for the 3"x5" of which I would need about 90) I would be spending over
$2k just on sensors, not including the equipment to process, record and
control them or the cost to actually have them built.

So if you, or anyone else, has any recommendations for some way I can
inexpensively measure the force of a hit, either some kind of rig to
use 2 or 3 small piezoresistive sensors that can accept accurate
readings from a 6"x24" curved contact area, I would appreciate any
ideas.

 

[[email protected]]

Stanislaw,

I've been doing some research into Strain Guages and I don't know if it
would work for my application only because according to the description
on Wikipedia, "as the object is deformed, the foil is deformed, causing
it's electrical resistance to change", and the object the user would be
hitting is a 8" diameter steel vertical cylinder. Unless we're
counting micro-deformations, the "object" shouldn't deform. But I
understand the principle, it's the same as the piezoresistive force
sensors just instead of using a chemical pressure sensitive ink, the
strain gauges cause variable resistance based on the shape.

I know this goes against most all electrical engineering ideals, but
this system doesn't have to be super accurate. Even rounding to the
nearest pound or point of a pound of force would be sufficient. Hence
why I said I'm considering not using force sensors at all for one
model. I've contacted Tekscan and described what I needed thoroughly
with them and they said that their product is 100% suited for my
application. The only problem is that I can't afford, personally or as
a per-unit cost, to have a custom run of 10,000 sensors made to my size
requirements and their standard "off the shelf" sensors are the size of
a penny and I need a contact area of roughly 6" tall by 24" wide. They
have some leftover sensors from the company that makes those force
sensing brake pedals so that trailer brakes can be applied in addition
to the truck brakes, but they don't make a habit of selling other
people's leftover custom sensor designs, and those are only 3"x5"
anyway.

Basically it comes down to cost versus accuracy. I need to keep the
per-unit cost of my system down under the $1k range to make it
affordable for my prospective clients but I want to give them the best
experience for their buck. For what I'm doing, there are other
products on the market, but in my opinion, they don't fulfill the needs
of their (our) target market.

And just as additional info to take into consideration for the cost
projection, I need either 15 6"x24" sensors or 45 6"x8" sensors to
complete each unit. Using Tekscan's estimate of about $25 per sensor
(for the 3"x5" of which I would need about 90) I would be spending over
$2k just on sensors, not including the equipment to process, record and
control them or the cost to actually have them built.

So if you, or anyone else, has any recommendations for some way I can
inexpensively measure the force of a hit, either some kind of rig to
use 2 or 3 small piezoresistive sensors that can accept accurate
readings from a 6"x24" curved contact area, I would appreciate any
ideas.

Oh, one more thing, I thought of this last night.

What if I had some kind of extremely thin rubber air chamber created
that could wrap around the steel tube and put an air pressure sensor on
it. So when it's impacted, the force of the air could be measured and
it wouldn't require expensive piezoresistive sensors?

Just a thought.

- Jace

 

[Baron]

Oh, one more thing, I thought of this last night.

What if I had some kind of extremely thin rubber air chamber created
that could wrap around the steel tube and put an air pressure sensor
on
it. So when it's impacted, the force of the air could be measured
and it wouldn't require expensive piezoresistive sensors?

Just a thought.

- Jace

Based on this and previous posts you could just as well use a
microphone !

 

[[email protected]]

Based on this and previous posts you could just as well use a
microphone !

Baron,

Not sure if that's a joke or not? If not, what do you mean?

- Jace

 

[Baron]

Baron,

Not sure if that's a joke or not? If not, what do you mean?

- Jace

No ! It wasn't. Impact implies vibration=noise. Something acoustic ?

 

[[email protected]]

No ! It wasn't. Impact implies vibration=noise. Something acoustic ?

Ok, that makes sense but do you think a system could be setup to use
the vibration to detect the force though?

The padding would absorb some of the impact and depending on what
direction the device is hit from, it might not register the same force
if it was from the front or the side?

I love the suggestion and would be interested if anyone could elaborate
how something like that would work. If that is a plausible solution,
it would remove all wearable parts from the impact surface which would
lower maintenance costs considerably considering the machine is
literally getting beaten to death.

- Jace

 

[Baron]

Well since there selling you something, they would, wouldn't they ?

Just what is the target market ?

Ok, that makes sense but do you think a system could be setup to use
the vibration to detect the force though?

The padding would absorb some of the impact and depending on what
direction the device is hit from, it might not register the same
force if it was from the front or the side?

I love the suggestion and would be interested if anyone could
elaborate how something like that would work. If that is a
plausible solution, it would remove all wearable parts from the
impact surface which would lower maintenance costs considerably
considering the machine is literally getting beaten to death.

- Jace

Flying by the seat of my pants here...... You describe a hollow
cylinder! Is it closed at both ends ? What does the cylinder
contain ? How is it mounted ?

You describe that it is hit (Impacted.) Your words. In what way ?
from what direction ? What with ?

 

[Stanislaw Flatto]

Not sure if that's a joke or not? If not, what do you mean?

- Jace

It has meaning for me;^)
Baron went the physical way, what physical quantity you want to record,
in what accuracy, and suggested a "sensor?" that responds to those
requirements.
My mistake was taking your description of _impact_ literally, and when
you gave your proposed dimentions of areas involved, I comprehended that
"impact" is nowhere in neighbourhood. The 'normal' impact wave in any
kind of solid is much smaller than those dimentions. So you are
measuring force, transitional or static, so use a load cell ( four
strain gauges) and get the signal from that. Easy.
(On 100.000lb load cell we ?weighed? a 60kg person to 1kg precission,
and recorded a hammer hit "impact"; just for fun)
But the equipment we used is out of the use for casual customers, our
sworn accuracy was 1% or better on static _and_ dynamic readings. Full
stop, and the design people sometimes required better answers and got them.

Have fun

Stanislaw

 

[[email protected]]

Well since there selling you something, they would, wouldn't they ?


Just what is the target market ?


Flying by the seat of my pants here...... You describe a hollow
cylinder! Is it closed at both ends ? What does the cylinder
contain ? How is it mounted ?

You describe that it is hit (Impacted.) Your words. In what way ?
from what direction ? What with ?

Stanislaw,

I'm not sure I'm 100% on the same wavelength as you. I did mean impact
in the literal sense. I am going to physically whack the machine with
a blunt object, be it a fist, foot or weapon of some sort. The area
that would be struck can be anywhere on the circumference of the steel
pipe that is facing the user, hence why I can't use a single small
sensor at a specific point. It would be as if you wrapped a parking
meter with sensors and then started wacking it with a stick. Inside
the parking meter would be the measurement equipment.


Baron,

The target market is for entertainment / sports / fitness applications.

The cylinder is hollow, standing vertically with the circuitry inside
and is capped at the top and the bottom is fastened to the floor. It
is hit with a large blunt object. The user can choose to hit it with
their fist, foot or use a weapon, most likely a staff or some sort of
club. Think of a bop the weasel game but instead of the weasel you're
aiming for lights and hitting this cylinder instead of weasel heads.

That's about as detailed as I can get without describing the rest of my
machine and nullifying the whole point of selling it . But basically
it's a sports machine that can be used for entertainment and physical
training. It has multiple components but this is the only one that I'm
stuck on; the rest have already been worked out.

- Jace

 

[Baron]

Stanislaw,

I'm not sure I'm 100% on the same wavelength as you. I did mean
impact
in the literal sense. I am going to physically whack the machine
with
a blunt object, be it a fist, foot or weapon of some sort. The area
that would be struck can be anywhere on the circumference of the
steel pipe that is facing the user, hence why I can't use a single
small
sensor at a specific point. It would be as if you wrapped a parking
meter with sensors and then started wacking it with a stick. Inside
the parking meter would be the measurement equipment.


Baron,

The target market is for entertainment / sports / fitness
applications.

The cylinder is hollow, standing vertically with the circuitry
inside
and is capped at the top and the bottom is fastened to the floor.
It
is hit with a large blunt object. The user can choose to hit it
with their fist, foot or use a weapon, most likely a staff or some
sort of club. Think of a bop the weasel game but instead of the
weasel you're aiming for lights and hitting this cylinder instead of
weasel heads.

That's about as detailed as I can get without describing the rest of
my
machine and nullifying the whole point of selling it . But
basically it's a sports machine that can be used for entertainment
and physical
training. It has multiple components but this is the only one that
I'm stuck on; the rest have already been worked out.

- Jace

OK ! I get the picture. Use a simple microphone capsule, say
electret. Take the signal from it and manipulate it to get what you
want. Amplitude will tell you how hard the device was thumped and the
frequency will tell you where.

Obviously you are going to have to play around a little to get the
optimum mounting/location for the mic. I would suggest suspending it
on a stalk inside near the bottom but above any circuits.

 

[[email protected]]

OK ! I get the picture. Use a simple microphone capsule, say
electret. Take the signal from it and manipulate it to get what you
want. Amplitude will tell you how hard the device was thumped and the
frequency will tell you where.

Obviously you are going to have to play around a little to get the
optimum mounting/location for the mic. I would suggest suspending it
on a stalk inside near the bottom but above any circuits.

Baron,

I appreciate the idea but I still don't think it'll work for my
application only because, and this is my fault for not including it,
there are 5 different sections on the tube that are to be impacted and
I think it would be too difficult to try to pinpoint which section was
hit with the microphone setup.

Again, thanks for the info and sorry I left that detail out.

- Jace

 

[jasen]

Baron,

I appreciate the idea but I still don't think it'll work for my
application only because, and this is my fault for not including it,
there are 5 different sections on the tube that are to be impacted and
I think it would be too difficult to try to pinpoint which section was
hit with the microphone setup.

Again, thanks for the info and sorry I left that detail out.

- Jace

put four or five microphones in it and the impact point can be determined
by the time-lag between the microphone responses.

 

[Pete Verdon]

Baron wrote:

I appreciate the idea but I still don't think it'll work for my
application only because, and this is my fault for not including it,
there are 5 different sections on the tube that are to be impacted and
I think it would be too difficult to try to pinpoint which section was
hit with the microphone setup.

In theory at least, it should be possible to identify where in a known
tube the sound originated by analysing the waveform produced by the
microphone. In practice this may not be sufficiently accurate, or may
simply be too hard a signal-processing problem to be worthwhile. In any
case, the fact that your tube could be hit with nearly anything, rather
than a known striker, probably rules out any detection based on sound.

I think the best idea so far is the air-bladder one, or possibly a
variation using some kind of liquid or gel in the bladder.

Pete