Need one.
I'm looking for a sensor to measure the force of impact. Specifically the impact of a soccer ball on a solid target. It does not have to be accurate, it will not be calibrated or calibrate-able. Just needs return a value that increases with force.
Any ideas?
ADXL375 accelerometer
That may just work. Any breakout boards available?
I've used a piezo disk for detecting impacts on a surface. Perhaps it's not the best sensor for that purpose, but it's certainly cheap and simple, and it worked perfectly for my application (which was detecting impact with much less force than yours). I got the idea from remembering the common "Knock Sensor" projects. You would need to make sure to set it up so that the voltages generated by the impacts were within the range of the ADC.
I saw the knock sensor projects as well, but wasn’t sure if I could get a sample rate high enough to capture the peak magnitude of the impact. The accelerometer looks like it has an internal peak capture.
Any breakout boards available?
Yes, there are several. There are more for the ADXL377, which is analog, also 200g.
Both are designed to measure impact accelerations.
adwsystems:
I saw the knock sensor projects as well, but wasn’t sure if I could get a sample rate high enough to capture the peak magnitude of the impact. The accelerometer looks like it has an internal peak capture.
The Uno max analog sample rate (out of the box) of 9kSPS is going to be quite enough to capture a soccer ball
bounce, lets say it travels at 20m/s, thats about 2.2mm per sample! A soccer ball is going to deform many
cm during the impact, it won’t be hard to integrate the samples in question for a good measure of momentum
and the peak reading will be pretty accurately representative of the peak force.
Doesn't the use of an accelerometer mean that whatever the sensor is mounted to has to accelerate, which means it needs to move and change speed?
If I mount the accelerometer to a wall, what would it read when the soccer ball hit? I would expect 0.
The impact causes the wall to move a small amount, and the accelerometer along with it.
I'm looking for a sensor to measure the force of impact
Study hints:
The accelerometer measures acceleration.
Force is mass times acceleration.
Newton's Third Law: for every force, there is an equal and opposite reaction force.
pert:
The impact causes the wall to move a small amount, and the accelerometer along with it.
So the backstop does have to move in order for the accelerometer to read.
I'm trying to determine, with 200g of range and mounted to the center a piece of 4'x4'x1/2" piece of plywood hanging from the top edge (ie., hinged) impacted by a 16 ounce soccer ball, will the sensor read anything? What range of reading could be expected? How does the readings depend on the weight of the backstop?
Try it and see.
jremington:
Study hints:The accelerometer measures acceleration.
Force is mass times acceleration.
Newton’s Third Law: for every force, there is an equal and opposite reaction force.
No kidding, hence the thread. The ask was for an impact sensor, then direction has gone the way of using accelerometers. I’m trying to figure out how to make it work.
jremington:
Try it and see.
Don't really want to spend $30 on a sensor that won't work. I'm trying to make sure I buy one with the correct range for the setup.
What is the informed basis for your decision to use a 200 g acceleration sensor?
If you are not capable of making a reasonable estimate of the acceleration experienced by a soccer ball when it impacts a surface, how do you plan to interpret any measurements you might make?
Start here: soccer ball impact force - Google Search
jremington:
What is the informed basis for your decision to use a 200 g acceleration sensor?
I haven't decided to use it. Hence the question. I'm trying to determine if it is the range sensor to use.
jremington:
If you are not capable of making a reasonable estimate of the acceleration experienced by a soccer ball when it impacts a surface, how do you plan to interpret any measurements you might make?
Hence the questions. I'm trying to remember my physics classes from 22 years ago. That's not going so well. In the end the exact number doesn't matter. But for the design phase, I need to determine of the sensor is one of the correct range and sensitivity to make sure it will read something non-zero and the maximum value. It is not of much use if it only read 0 or max all the time.
If you are serious about this project, you will have to spend some time with the available literature. For example, this study
https://www.researchgate.net/publication/264275648_A_Study_of_Impact_Force_on_Modern_Soccer_Balls
shows that the acceleration of the ball, during a machine-driven kick, ranges from about 200 to 600 g.
The acceleration of a large surface impacted by the ball will be proportionally less by the ratio of the masses.
jremington:
If you are serious about this project, you will have to spend some time with the available literature.
I always get a kick out of this assumption. But what needs to be evaluated is the impact of the backstop design on the readings or operation of the device), which is partially independent of the force from the soccer ball. It can be any force applied, but come back to how the design of the backstop affects the operation of the accelerometer.
It’s all about the keywords. I just found something similar.
F=mA, F=0.5 * (200 * 9.8) / 4.448 = 220 pounds-force.
But the question remains, what is the mounting requirements for the sensor? How does the design of the backstop affect the readings (or what are is the best design characteristics for the backstop)? Should it be heavier, lighter, light and bottom weighted, or?
I always get a kick out of this assumption.
Good to know, thanks!
Mount it on some kind of springs. If you hit it in the center, the deflection for a given soccerball velocity should have a high degree of repeatability.
The pressure in the soccer ball will have some effect. The mass of the plywood will affect it, the heavier the plywood, the smaller the acceleration.
The springs will of course affect the acceleration, too, if they are very stiff or are initially pulled tight.
This will be an elastic collision.
