Hit Plate impact detection for .22 Long Rifle ammunition

Projects General Guidance
1

Hello, I'm trying to build automatic target detection system for .22 Long Rifle ammunition, the hit plate is gonna be made of stainless steel and the ammunition is lead

The idea is to use some kind of sensor to detect impact on the hitPlate which you can on the picture here

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so I can use that data to show scores and move some motors to do various actions

My first try is to use piezo disk to detect it, but not sure if it's the right way to do it or not

I'm also thinking about using Force Sensor.

Would be nice to get some help about what to use, the best approach for that.

Thank you.

2

Also here is how I tried to wire it with piezo disk

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3

Should work.

In the Arduino IDE, use Ctrl T or CMD T to format your code then copy the complete sketch.

Use the </> icon from the ‘reply menu’ to attach the copied sketch.

4

You might need to condition the piezo signal in some fashion.

Link to the spec sheet on the piezo's being used?

5

IIRC there is a "knock sensor" sketch for the use of piezo sensors.
But as Idaho states you need to give the specs of the sensor as there are a lot of variations out there.

Other knock sensor sources

6

It's just a normal piezo disk, from where I bought it they don't provide any spec sheet :neutral_face:

7

What happens when you try the setup you have? People have reported using a piezo disk and an Arduino to detect a pin drop on a desk.

8

I can read the values, but sometimes I get high value sometimes I get low value, even I'm hitting the plate the almost the same way, I'm not trying to make it too sensitive since I only wanna detect an ammo hitting it

9

Does the sensor have any markings on it at all ?

10

Connect the piezo to the inputs of an opto-isolator and connect the opto outputs to Arduino GND and an IO pin set as INPUT_PULLUP.

11

Piezo disks can generate some high values albeit for short period of time. I wouldn't use an opto isolator as I don't see a piezo reliably powering the required input.

What you need to do is limit the voltage from the Piezo to the Arduino with a 5V TVS or Zener, then add a 10k between the zener and the Arduino digital input.

I cannot imagine a .22 hitting the disk and not getting a huge voltage spike from the piezo.

One could add a mass on the back side of the piezo but I doubt it will be needed.

Mounting: I can't see what holds the piezo to the disk. The best attachment would be a relatively hard epoxy.

12

Possibly non acid silicone would be much better.

13

Possibly non acid silicone would be much better.

That is your logic for your recommendation of silicone for attachment?

Silicone rubber will absorb and dissipate some of the impact, hence a harder material is recommended.

14

Now I may be being silly here but I am very curious how well an accelerometer, even a hobby grade one, would detect the impact.

If the OP ever decides on using an accelerometer post the results here.

15

Whereas I Have Done This and it's not a problem at all. Others have put videos up connecting leds directly to show. --- Semiconductor junctions flatten the spikes. --- I went as far as repeatedly smacking the disk with the butt of a screwdriver handle to get longer pulses. I tested one disk to destruction and no other parts smoked hard as I went for smoke.

I can't imagine a fry pan stainless steel disk that will stop a .22 long rifle bullet yet be so light that the transferred momentum shock will be as hard on a disk as the whole force of my screwdriver handle directly on the disk.

My experience with .22 LR is a few 1000 rounds spent target shooting to collect NRA medals for 3 years or so. I don't have to dream about them, I have ballistics tables.

16

I’d be tempted to put an op amp in to help capture and condition the pulse .

17

Take a look at a similar project here

18

I'm planning on squeezing it between the plate and another pice of metal that will be screwed to the plate to give it stability and get the full power of the hit is it logical ?

19

The plate will be stationary, and it will be connected to a frame that contain 5 plates together

This is the picture of the product I'm trying to recreate for my self

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HoRa2000E-1920w.JPG copy1024×770 664 KB

20

Thank you I checked it, but he is using vibration sensor which can't work for my case for reasons I explained on the comment above this one.