Spacer same or better if .002 thicker than Velostat.

 

Thanks for the reply, Sophie! I agree that a drawing is often easier to understand than text, and my very first post has a PDF file attached to it with a sketch of what I originally had in mind. I first did that document as a PNG file, but redid it after reading in the forum guidelines that PDF was the preferred format.

In response to my original post, I received some excellent suggestions that would help me with that approach, suggestions about using sound or vibration to detect when the plastic ball strikes the target, and a suggestion from Bernard to look into using a sheet of Velostat between two pieces of aluminum foil as the target.

As Bernard made suggestions and I worked on figuring out how to implement them, I attached PDF drawings to several of my posts to confirm I understood what Bernard had in mind. I believe the vast majority of the text in this thread consists of questions, comments, and suggestions about the information on those drawings.

If I'm wrong about attaching PDF files being the preferred method of sharing drawings in this forum, I'll be happy to switch to a different file format for any future drawings I upload.

Thanks again for your reply.

yeah , i understood, because quick glance at image saves a lot of time

 

Will aluminum foil be robust enough? What about stainless shim shock. It's expensive though.

 

Just to muddy the water a bit, if a secondary target is desired it is possible to form it in the bottom AL layer just bring out a connector for each piece. If the Velostat is large enough the whole board could be covered with AL & divided up into maybe 9 targets & maybe a smaller target within the 8" X 18" main target. Another thought; the spaces between AL sheets should not allow the Velostat to become stuck to bottom adhesive layer, just small paper spacers should do.

 

Will aluminum foil be robust enough? What about stainless shim shock. It's expensive though.

I forget what I calculated as the number of times a plastic ball might strike the target area in the course of a year, but off the top of my head I'm thinking it will be less than 300,000.

If the Velostat target works and the aluminum foil lasts less than six months, I'll have to look for an alternative to the aluminum foil.

 

Spacer same or better if .002 thicker than Velostat.

I ordered a 4' x 3' sheet of Velostat, and am going to use less than 2 square feet of that for the target. Instead of cutting stacks of paper to make a spacer that goes around the edges of the Velostat, is there any reason I couldn't make the spacer out of Velostat and one sheet of paper?

 

I guess that you could skip layer # 6, spacer. Keep #3, spacer.

 

Example of sensor life might be that FSR 400 series pressure sensors are tested to 10M cycles & these are around 1" dia. Velostat + other supporting materials. So- there is hope. Might have to patch outer film @ some point? My fingers are crossed.

 

Example of sensor life might be that FSR 400 series pressure sensors are tested to 10M cycles & these are around 1" dia. Velostat + other supporting materials. So- there is hope. Might have to patch outer film @ some point? My fingers are crossed.

Thanks again for your help!

The Velostat I ordered arrived yesterday, and I cobbled together a test target.

The first "go/no go" portion of this is whether or not a pickleball bouncing off the target plays about the same as a pickleball bouncing off the portion of the playing surface not covered by the target. On this count, the Velostat target passes with flying colors.

My original plan was to have some sort of simple switch(es) that would be tripped when the ball hit the target. Hit the target, trip the switch, sound the chime.

My experience with a multi-tester has pretty much been checking continuity with the Ohm meter and checking the voltage of electrical outlets and batteries.

When I connect the leads from the multi-tester to the aluminum foil "leads" from the target, current flows through the target when everything is at rest. I believe this means that using the Velostat target will result in a small, constant drain on the battery - even when the target has not been struck.

I believe it also means that instead of being triggered through a binary off/on switch, a circuit to sound a chime would be triggered by a drop in the amount of resistance there is to the electrical signal traveling from one piece of aluminum foil, through the Velostat, and into the second piece of aluminum foil.

It is no surprise to me that striking the target with the ball has no appreciable effect on the multi-tester and does not result in the multi-tester's continuity buzzer sounding - the signal comes and goes so quickly that my device cannot respond in time. Just FYI, the continuity buzzer does sound if I press and hold the pickleball against the target.

Am I correct in my guess that the circuit to sound the chime will be triggered by the change resistance and not the opening and closing of a switch?

I put together a video that shows the multitester readings for various connections of the unit's leads, along with what the multitestor does when the ball hits the target. You'll find it at

Thanks again for your help!

 

What scale is meter on? The AL foil sheets & Velostat need to be as flat & wrinkle free as possible to keep the sensor resistance as high as possible, around 1k.
Try to aim for 3:1 or better. If necessary the target can be subdivided to keep R high then ORd to give one signal. Recheck post # 23 & # 31.

 

I have one for you, cut the ball in half put strips of Magnetic pieces like the stuff inside a refrigerator door seal. Then put Hall effect sensors on the opposite side of the acrylic sheet.

kv

 

What scale is meter on? The AL foil sheets & Velostat need to be as flat & wrinkle free as possible to keep the sensor resistance as high as possible, around 1k.
Try to aim for 3:1 or better. If necessary the target can be subdivided to keep R high then ORd to give one signal. Recheck post # 23 & # 31.

Thanks again for your help!

The selector switch is set a "x1k," so I'm guessing the answer to your question about the scale is 1000.

I don't, unfortunately, know what you mean by trying to aim for 3:1, and is 2:1 better than 3:1 or is 4:1 better than 3:1?

If I was on a game show and had to guess what you mean by aiming for 3:1, I'd say the meter should read something more than 600 ohms at rest, and less than 200 ohms when I press and hold on the target with the ball.

If I attach leads to 2 loose sheets of aluminum foils and separate them with a sheet of Velostat, on a 10x scale, my meter sometime reads Infinity and sometime reads more than 600 ohms. When I press on and hold the top sheet of foil with my finger, the reading drops to below 50 ohms. Is that the sort of performance I should be trying to get from the sensor?

Thanks again!

 

Information from post # 72 much more helpful than meter readings.
600 ohms vs. 50 =12:1 = great. Drain @ 600 ohms about 8 mA or 250 hours on AA alk. batteries. That is why we want to keep resistance high as
possible. If resistance is as low as 300 ohms we might want to use a comparator for hit detector. My test sensor, 10" X 12" gave 5k so 8" X 18"
could possibly be as high as 6k ohms?

 

Information from post # 72 much more helpful than meter readings.
600 ohms vs. 50 =12:1 = great. Drain @ 600 ohms about 8 mA or 250 hours on AA alk. batteries. That is why we want to keep resistance high as
possible. If resistance is as low as 300 ohms we might want to use a comparator for hit detector. My test sensor, 10" X 12" gave 5k so 8" X 18"
could possibly be as high as 6k ohms?

Just to be clear - the numbers I put into post #72 were not actual readings. I the numbers out of the air as easy to multiply values that would help see if I understood what you meant by a 3:1 ratio.

Some other info:
- the test target I cobbled together is smaller that I anticipated the working target to be. I found, however, that the test target was big enough for my needs. If I recall correctly, the piece of Velostat I used was 10" wide x 8" high, so that will be the size I'll work with on the final target.

- I cut a rectangle out of the 10" x 8" piece of Velostat, leaving an interior piece of approximately 9.4375" x 7.4375", with a 1/4" border of Velostat and paper around all 4 sides.

- When I started using the demo target, the interior piece of Velostat slid down, so it was touching the border on the bottom. When I make my next target, I'll put a small piece of double-sided tape in each corner of the Velostat so it won't slide and I'll have a slip gap on all 4 sides between the interior Velostat and the border.

 

You say that post# 72 measurements are not real ? They are close to what I would expect; ball pressure measured is about 50 ohms to 200 ohms & no pressure 1k ohms to 5k ohms on 10" X 12" target.
There was no need to cut the Velostst to form a spacer, my bad in not explaining that in post#67.
In the video, how thick is the acrylic sheet ? , & was the sheet still in place for the live ball strikes ?

 

If post # 72, last paragraph, is not a real measurement then we have no proof that your "Velostat" is a pressure sensitive film. Could you humor an old ( 93 )man & measure the resistance between two AL sheets which are separated by a sheet of " Velostat",lying on a flat surface, first with no added pressure & second
with thumb pressure ?

 

If post # 72, last paragraph, is not a real measurement then we have no proof that your "Velostat" is a pressure sensitive film. Could you humor an old ( 93 )man & measure the resistance between two AL sheets which are separated by a sheet of " Velostat",lying on a flat surface, first with no added pressure & second
with thumb pressure ?

Bernard, I created and teach a 2-Day "Basic Hydraulics" course. I visit a company's site, and by the end of the course, mechanics who had been trying to fix hydraulic problems through trial and error are able to dramatically reduce their company's hydraulic-related downtime because they understand what all their hydraulic components and systems do, can read hydraulic schematics, and know what it takes to get the longest, most productive life from hydraulic components and systems.

But when it comes to electronics like this sensor circuit, I don't know enough to know what I don't know.

For example, the only thing I've ever done with the ohm function on my multitestor is to check for continuity. Touch one lead here, touch the other lead there, and if the meter screeches, I'm good. I didn't remember until last night that before taking a reading with the meter's ohm function, I need to touch the leads together calibrate the meter to 0.

The quick answer to your question is, yes, my Velostat is pressure sensitive film. In addition to showing that I didn't remember I had to calibrate the meter, the tests you requested are among those I put in the video I attached to post 69.

It occurred to me that, while the layer of aluminum the ball strikes need to be very thin, the sensor "sandwich" would probably function better if the bottom layer of aluminum was thicker. I have a roll of 6" wide aluminum gutter screening, and attached a 15" long piece of it to the playing surface yesterday, and it does not seem to affect the way the ball plays.

The readings on my multitestor are the same with a "gutter screening/Velostat/aluminum foil" sandwich as they are with an aluminum foil and Velostat sandwich, so I'm making another test sensor with the 6" x 15" gutter screening as the base. I'll let you know the readings after I get it made and tested. If it works, my next-door neighbor recently had her aluminum siding replaced and I've got a piece of her siding I can sand clean and use for the final version.

I'll get back to you when I've got this next test assembly done.

 

The bottom layer , target, can be any thickness of AL foil.

 

The bottom layer , target, can be any thickness of AL foil.

Bernard, thanks again for all your help!

I made another test target, using the aluminum gutter guard as the bottom aluminum layer, along with adhesive backing and a protective plastic coating on top.

The attached file shows the display of my meter after calibrating it to 0 and setting it to the "X1K" scale.

At rest, I believe it is showing resistance of right around 4 ohms (or is it 4,000 ohms?). With a ball pressed and held against the target, the second image shows right almost no resistance. I think that means it meets your suggested "3 to 1 or better."

I am, however, going to have to put building the chime circuitry on hold for a while. I think I mentioned in an earlier message that I'm in the process of converting some of my on-site training into a live, interactive online Basic Hydraulics Boot Camp. I just got hired to teach the not-yet-completed Boot Camp, and I need to revise a bunch of my in-person material so it is easy to understand when seen onilne.

I'll get back to this hit counter project after I've got the Boot Camp done and tested.

Thanks again, and I hope you're still available and willing to help at that time.

 

Great results, about 13:1. I also made a sensor, 5" X 7" as in Pickle Ball Target. 5V supply( 4- NiMH AAs ), 4.7k pull up resistor, idle = 4.5 V, ball hit = less than 1v
Standby battery drain about 250 micro A from target.
See you when you return.