The OP has posted only once. We're preaching to the choir- but still interesting.

My guess is either he suffered a tragic accident on the range or learned how to aim. As shortbus observed, it is kind of a given that you hit somewhere on the whole target. Otherwise, you should move it closer.

John

 

I am still here. Got tied up with work. I'm going to read through the posts tommorrow morning in greater detail. Hopefully I will address everyone's concerns.

 

First off, the design has change a bit since my first post. The target is no longer suspended, it will not be supported. Picture a box on the ground. Two arms extending up from the sides of the box. A cross member on top of the frame, that will clamp the target. Target is clamped into the cross member, target frame is mounted upright, tensioning springs will ensure that the frame drops backwards when a hit is triggered.

I suppose my first thought is that the frame will be locked into place via a solenoid or linear actuator, when the target is hit, a sensor will trigger the solenoid or actuator to pull back and the tension springs pull the frame down.

I think I might embed some magnets in the frame for a magnetic reed switch or put in a micro switch to detect the frame drop. That switch will trigger a motor to rotate the frame back into an upright position, and the solenoid or actuator will lock the frame back to being upright.

Here is how it will work:

· Unpack fully assemble system

· Plug system into power. Ensure that the system remains off.

· Manually set the target support frame into an upright position.

· Insert target into clamping mechanism

· Turn system on.

· Fire round at target.

· Sensor detects hit on target. Trigger actuator/solenoid.

· Solenoid releases support frame. Release of support frame turns off sensor, so that the actuator won’t keep triggering.

· Once frame is down, triggers motor to rotate frame back up. (Not sure if it will be direct drive to frame or chain drive to shaft.)

· One frame is back up, actuator will relock the frame up right, causing the motor to stop. (Not sure if I am just going to put the motor on a timer, or putting a magnetic reed switch to stop motor)

· The circuit should be reset now and ready to operate again. Once targeting is done. Turn off system, release target from clamp.

This system has to be as mechanical as possible. I need as few electronic components as possible. Something to sense vibrations, solenoid or actuator, relays, motor, possibly a couple timers, and some switches, voltage regulators. I haven't gotten all of that sorted just yet. Electrically, I wanted to start from the sensing aspect first. As this is my weakest area of knowledge.

I will attempt to answer questions or make comments based on y'alls posts below.

I would go with a microphone placed against the paper or metal frame.

There are also piezo "contact microphones", essentially a piezo buzzer but wired to detect an impact or noise (like using a speaker as a microphone).

GopherT- I can no longer use optical detection. It needs to detect the vibration of the paper, when it is struck.

A wireless camera would give definitive information.

wayneh- Camera sysem is no longer an option.

Bullet speed, diameter, shape, and paper density, will have a big impact on the wave energy imposed on the paper. A .223 diameter bullet traveling at 3000 ft/sec will create a much different wave, (or sound), than a .450 diameter bullet traveling at 850 ft/sec. Suggest you get an inducer and a data recorder and take a lot of data.

There are optical bullet sensors used in "Chronographs". These are used to measure bullet speed. I suggest you put your energy into that area.

Lestraveled- You are correct. all of those variables play into account. I don't want to limit my sensor based on what one bullet does to one target though. I want to beable to shoot and bullet at any target that will fit into the cross memeber.

There are color sensors that will output RGB channels in digital format. You could use this to detect a significant color change. So for example: you would set up a target and hit the "reset" button, the device would sample the color it sees and keep that in memory. Every time a bullet hits, it would detect a color change (say 10% difference). Any less than that (shadows, clouds, whatever) and the system would ignore it.

https://www.sparkfun.com/products/10904

This is the best way I can think of.

A vibration sensor might be hard to fine tune, considering you want it to move... Motors cause vibrations.

matthew798- The color sensor sounds a bit complex to setup and to trouble shoot out in the field. I think I want to go the route of vibration/impact detection. I will have to figure out a way to turn off the sensor when the frame, I was thinking about some sort of magnetic reed switch, so the sensor wouldn't get power if the frame wasn't upright and locked

I am assuming it is a pellet/air soft gun. Otherwise any device near or in contact with the paper or frame will be at risk of destruction. Please describe the situation a bit better.

GopherT- Primary munition is a .223, coming from an AR-15. I asked about potential damage to the unit, I was told " If they can't hit the target on the backstop, they wont be allowed to fire at this." Apparently this targeting system will only be used by trained professionals. That being said, I think the system sits behind sandbags as to limit possible damaged. They don't seemed to worried about hitting it.

I would expect that a hit would cause a distinct pressure wave behind the paper target that would be very different from any other external sources of noise or vibration. One or more microphones mounted around or within the back of the frame would probably suffice.

blocco a spirale- Yes. I am no expert, but it would seem to me that different rounds would give off different pressure waves from different distances. I don't want something I need to fine tune accordingly.

There are impact sensors used to detect rough handling of delicate cargo (kind of seismic sensor) or tilt sensors (which once activated cannot be reset) also for the same purpose, probably not suitable but worth to look at.

BTW, have you considere that whatever you choose must be 100% sure that could be not damaged by a "creative" shooter? Those exist but maybe you know that.

atferrari- I would definitley need something that can be reset.

That's very cool.

Here's the standard solution to the OP's application. Too expensive?

View attachment 76715

wayneh- They aren't worried about where they hit the target after each shot. Just that the target drops after a strike and comes back up. I don't know exactly why they want it this way, as I don't shoot rifles much. I just shoot skeet and even then its only 3-4 times a year.

Has anyone read the first post? The OP is not concerned with the speed of the bullet nor with just knowing by visual means that the target has been hit.

blocco a spirale- Correct. I need something that can detect an impact.

There a couple of old threads. Search for, "paper target".

#12- I will look into them. Thanks

 

Personal I think the speaker suggestion to detect the air pressure increase when the target is hit would be the best. Even that would be difficult to implement. I'm thinking you may need some kind of baffle behind the paper to contain and maybe even direct the sound wave. The back would have to be open or replaceable, open may not work very well.


OK, A thin box with a replaceable back, mount the speaker or mic on the bottom with a hole so the air pressure can get to it, protected by a steel plate. Steel plate could also double for your pivot to rotate the target. Outline the front of the box with small but thick angle iron with the point facing forward. This would deflect stray bullets and sorta protect the sides of the box. Make everything replicable, it will get shot up.

BReeves- I cannot have anything behind the target. The sensor will have to be in the cross member clamping mechanism, touching the target, so it will detect the strike. I need as few parts as possible, as replaceable back would not work for this application.

microphone methods would not be practical, dont you know about the pressure wave that comes out of the muzzle just behind the bullet? a lot of noise. why not use a video camera with a vision system to detect the hole in the paper?

alfacliff- Optical is no longer an option. has to be vibration/pressure based.

This may have become an academic exercise since the OP's not checked in since posting. I know the answer to his question but I don't think I'm allowed to say. Very enigmatic of me, I know.

KJ6EAD- I would be interested in your answer, if you were allowed to say.

It should be very close to the paper piece (but no bonded to it), maybe in/on the supporting frame.


Should be not in the way of the bullets to avoid bad (and good) shooters.


Should be able to distinguish the effect of (strong) wind.


So, KJ, you are not going to disclose anything, right?


Intrigued, interested, curious myself.

atferrari- This is exactly how I was thinking about it.

Piezo mounted on metal frame should be able to detect vibrations from bullet impact.

ISB123- I think this is the route I need to go. but what kind of piezo do I need? Film? Wafer? How do I use that sensor to trigger a relay? I saw that there are piezoelectric momentary switches. Would those detect vibration?

Perhaps the OP can explain if/why he wants to avoid visual methods like everyone else uses.


I can't recommend trying to develop a new method without knowing exactly what's "wrong" with the standard method. Read the title of his post, and explain to me why the "best way" is not the current state of the art already in use.

wyaneh- I was told, "No optical. Make this as mechanical as possible."

Because he wants to automatically move the target following a hit.

blocco a spirale- You got it.

Oh, you mean like in a pinball game, hit the target and it zips away? I totally missed that part of it. What provides the power to move it?

wayneh- That was the original idea, for the target to be suspended. Now it is just going to drop back and return upright. The power will be provided via 12V-24V from vehicles or tractors. Also 120V if they plug it into a generator.

Regardless of what it is used to activate, the issue is still, what is the best method to detect a bullet passing through a paper target. So far there are two suggested methods, sonic and visual.


The visual method is tried and true, and is relatively simple.


The sonic method will require some kind of processing or filtering to discriminate between ambient gun shots (sound) and the wave created by a bullet passing through paper. The sonic wave from a gun shot will impact the entire target area, in this case 780 square inches. The bullet will only impact a very small area: .159 square inches for a 45 acp, and .04 square inches for a .223. That is a 1000 to 1 ratio at best. The paper will also want to resonate at one frequency. If the bullet passes through the paper close to the microphone, it might work. If the bullet passes through the paper far away from the microphone all the wave characteristics that make it different from a sound wave, will be lost.

Lestraveled- While I agree, that those may be the best ways. I do not have the know-how to program any of that. I was also told "No software, we want this as mechanical as possible." Thats why I need sensor, relay, actuator, motor, and switches. So anyone with basic electrical and mechanical abilities can repair/build it.

Here's another method to consider - accelerometer. I think the sharp, unidirectional spike from a strike on the target ought to be "easily" distinguished from ambient wind and noise.

wayneh- An accelerometer might work. I will look into that. But if the accelerometer doesnt move on all three axis', will it work? I only expect there to be a vibration from the impact, not much movement.

Not a shooter myself, but.... some time ago, I looked over a circuit meant to detect then a diesel injector fired. It was a diesel tachometer. It used a piezo device as a detector. I would try mounting the target to a frame with the device attached.

Brownout- I feel like peizo is the way to go as well.

Only way I can imagine is a computer analyzing an image captured with a camera.. Nothing simple about it..


I was once involved in an automated target project, wrote the software for the computer that controlled the micros out on the range which controlled the targets. The targets (10 targets each in 5 stations, 50 targets total) were steel and replaceable, the mechanism was air operated. Without air, the targets would fall just from being hit and a micro switch told the system when a target was hit. The software on the computer would raise and/or lower the targets depending on what scenario the shooter selected. All scenarios were timed and the computer reported to the shooter his time at the end. I still have all the technical stuff for this system and a demo board with 10 air cylinders. The original project crapped out when the range owner ran out of money, guess I now own it as he still owes me for some of the work I did. Anyone want to start marketing an automated target system, I could be bought.

BReeves- I am doing something similar, but with paper targets, no air. No software allowed for this project.

 

Knock detectors are common in cars these days. Piezoelectric accelerometers.


I think it would work (and suggested it in #26) but I'm leaning towards the optical method, since it has a history of successful use for this application.

I may be totally wrong on this, but hitting the "paper" has never been part of any target shooting I've ever seen or done. The object of target shooting is to hit the center of the target, not just the "paper" surrounding it. Which is how I read the original question, why would you want to know that the overall paper was hit? The center of the 'bullseye' is what is the object of target shooting is, and there has been/is another thread on how to make a target for that.

shortbus- I don't know why they want it this way. I was just told to make it work. I have the mechanical aspect down, i am working on the electrical aspect. I just don't know anything about sensors. I am sure they have their reasons as to why they want it this way. Perhaps the target they plan to use has a rippled numbered grid laid out on it and they are going to keep score. I didn't ask, and they didn't tell me. Once I get it built, I am sure they will demonstrate.

To me the objective is to simply sense a hit anywhere to trigger the movement of the target to another defined location.

I would simply achieve this with a simple hinged backing of sorts on the target (or frame around the target) with a microswitch. An impact would deflect the backing into the microswitch. Springs,etc.. could be used on this backing to ensure that a true bullet impact triggers the sensor and not wind movement,etc..

Of course there is the issue of this backing plate/frame being suitable to get the desired output without being a surface that would allow a ricochet or otherwise effect safety.

mcgyvr- You are right. Sense an hit, relocate the target, reset the target. Repeat. I cannot use a backing. Only the target.

Several years ago I was fortunate enough to get to tour the Barrett Arms facility,( the .50 caliber people) this was before the new addition. In the test range room they have a laptop computer on a shelf, on the screen is a target. On the bottom of the target is a place for the test shooters name, date, serial no.. The tester takes a new rifle from the hardcase, types serial number and name into computer. He then gets prone and fires 3 shots down the range tunnel at a target projected on the rear wall (bullet stop) 100 yds away.

Each shot shows up on the computer screen in real time, showing the point of impact on the target. When the 3 shots have been fired, and are within acceptable limits, the shooter clicks on "print" and the target prints out with 1/2" black circles where the bullet holes should be. The buyer then has a test target showing that his weapon has passed that part of QC.

I asked about the target, and neither the shooter or the man giving the tour knew anything about it. All they knew was you never have to go down range and you never run out of targets. I was able to speak to Chris Barrett afterwards and all he could tell me was " some sort of sensor eyes".

My guess is rows and columns like an old touch screen.

gerty- Sounds cool. Way to complex for me

muzzle blast from a .22 at 25 yards? not very much. the op sisnt specify the calibre of bullet. I have an old 1884 springfield trapdoor rifle that I can hear the bullet hit the backstop at 100 yards away. a littloe more muzzle blast too. there are many, especially military weapons , that are louder.

alfacliff- Primarily a .223 at 100 yards, but I don't want to limit it to that calibre or distance. So I don't this acoustical sensors will work for me. I want a vibration detection sensor of some kind.

The OP has posted only once. We're preaching to the choir- but still interesting.

Bernard- I promise I am still here.

 

Good stuff - much clearer now.

I guess you have the mechanical figured out but here is what I was thinking. Once triggered, everything you described is one cycle. So I visualized a single motor turning a cam with an arm. The mechanics are arranged to rapidly pull the target down to show the strike, and then slowly reset the target, all in one rotation of the cam wheel. I think you get the idea. Gravity or a spring might help pull the target down but the motor adds the energy to reset against gravity or against the spring.

The accelerometer and piezo ideas are essentially the same - just different words for vibration detection. I guess the distinction is that an accelerometer is able to provide directional information whereas a piezo, which is often part of an accelerometer, just reports that it hears something. To use an accelerometer, it would have to be touching the target paper so I imagine it would have to be built in to the clip that holds the paper, or possibly attached to the bottom of the target where it would serve as a weight, like a curtain weight to reduce fluttering.

I don't se how you could use the visual method already offered by lestraveled unless its window is well ahead or behind the target paper. It wouldn't tolerate the paper fluttering in and out of its plane of view. But this method is still a strong contender.

In my humble opinion an audio method would be difficult with the arrangement you've described, since the microphone would not be near the impacts. Unless one pointed a parabolic mike at the target, or one of those laser microphones you see in the spy movies. Hmmm... not a bad idea.

 

Which brings us all the way back to post #2, a CONTACT MICROPHONE - also known as a piezo transducer
http://makezine.com/projects/make-38-cameras-and-av/piezo-contact-mic/

 

Which brings us all the way back to post #2, a CONTACT MICROPHONE - also known as a piezo transducer
http://makezine.com/projects/make-38-cameras-and-av/piezo-contact-mic/

Forgive my ignorance, I dont see how I make this trigger a relay to trigger a solenoid? Do I run 12 votls to one side and it acts as a momentary switch?

 

Would something like this work?

http://www.schurter.com/var/schurte...s/document/datasheet/en/pdf/typ_PSE_EX_19.pdf

This is a piezoelectric switch. Which I assumes detects the vibration and switches a power source. This form factor world work nicely for my clamping mechanism. Plus it is IP69K.

 

Good stuff - much clearer now.

I guess you have the mechanical figured out but here is what I was thinking. Once triggered, everything you described is one cycle. So I visualized a single motor turning a cam with an arm. The mechanics are arranged to rapidly pull the target down to show the strike, and then slowly reset the target, all in one rotation of the cam wheel. I think you get the idea. Gravity or a spring might help pull the target down but the motor adds the energy to reset against gravity or against the spring.

The accelerometer and piezo ideas are essentially the same - just different words for vibration detection. I guess the distinction is that an accelerometer is able to provide directional information whereas a piezo, which is often part of an accelerometer, just reports that it hears something. To use an accelerometer, it would have to be touching the target paper so I imagine it would have to be built in to the clip that holds the paper, or possibly attached to the bottom of the target where it would serve as a weight, like a curtain weight to reduce fluttering.

I don't se how you could use the visual method already offered by lestraveled unless its window is well ahead or behind the target paper. It wouldn't tolerate the paper fluttering in and out of its plane of view. But this method is still a strong contender.

In my humble opinion an audio method would be difficult with the arrangement you've described, since the microphone would not be near the impacts. Unless one pointed a parabolic mike at the target, or one of those laser microphones you see in the spy movies. Hmmm... not a bad idea.

I thought about the cam, but that is something I would most likely have to get machined specific for my application. I am trying to get as many stock parts into the build as possible. These guys want to be able to pick up a McMaster-Carr catalog and order replacement parts if they want. That is why I was thinking about a direct drive motor or chain drive to a primary shaft. I found a motor with a half inch shaft that I plan to use. I just wasn't sure whether to go direct drive or chain drive. I'm leaning towards direct drive due to the least amount of parts.

 

Forgive my ignorance, I dont see how I make this trigger a relay to trigger a solenoid? Do I run 12 votls to one side and it acts as a momentary switch?

I don't know if it is sensitive enough. It looks like a defined solution with built in amp and comparator/latch to make a switch.

Something like this can be a starting point and you can build your own amp and control system that meets your sensitivities.

http://www.radioshack.com/piezo-element-1500-3000hz/2730073.html#.VInEhLwo7Dc

 

Forgive my ignorance, I dont see how I make this trigger a relay to trigger a solenoid? Do I run 12 votls to one side and it acts as a momentary switch?

I think everyone here has taken as given that the circuitry details are "simple" once the basic idea is fleshed out. Getting the circuit to produce a brief pulse, a 5-second pulse, latch a relay or trigger another circuit - this is all relatively easy stuff.

It is worth thinking about what the available power is. You mentioned batteries and that sounds good. Setting it to all run on 12V DC would give you the option of using auto batteries or using a mains-connected adapter if you want. If you know the motor you plan to use, post the specs here. The power demand of the motor will dictate some of the circuit design. Will it turn in one direction only?

 

I happen to have the proto type of a target mover I designed in the 90s. I was competing is USPSA. This is before I learned to weld.

I will see about posting a video of it working.

 

Remind me not to break into your basement.

 

Here is a video

OK, I bypassed the control section so that it would run continuously. There are micro switches that cause it to stop at certain points.

OK, Google/Youtube likes me now. Here is the video on Youtube:

How it works:
The motor lifts the target up using a "hook" attached to a pulley. If the motor is shut off at the top of the travel, the target will stay at max height. If the motor continues past max height, the hook releases, and the target drops to the lowest height.

 

Since your handlers say no to optical, lets look at what it would take to use a vibration sensor (microphone).
Suppose you attach a piezo mic to a paper target:
- What will it "hear" when a bullet passes through it.
Caliber
Velocity
Paper density

- Could you distinguish between the bullet impact and the gun shot sound?
- Could you distinguish between and bullet and wind ruffling the paper?

How many sensors, microphones, accelerometers would you have to try?

Are you starting to get the picture??? It will take a lot of time at the range, a lot of ammo, a very nice digital oscilloscope, a laptop, and good amplifier, a variety of sensors, etc,etc, just to get the data that will tell you if it has a chance at all of working. Sure, your handlers have said no to optical, but are they willing to pay the price just to find out if sonic will even work, let alone the expense of developing/building the actual electronics??

 

I assumed the "no optical" rule means "no human looking through a lens". If it runs deeper than that, let them know that they could get bullet velocity information if you can use an optical method. That might tilt the balance.

I agree with Lestraveled that, while the accelerometer strategy would probably work, there is definitely a lot of work ahead in getting to a reliable solution. Considering that a known technology - one that's easy to implement - is already available, it's hard to argue for inventing a new system.

Here's a thought experiment: If a human was standing to the side of the target with his fingers holding the edge of it, would he be able to hear and/or feel the impact on the target? I think the answer depends at least a little on the paper the target is made of. A mylar sheet behind the paper would make a heck of a racket, I think.

 

wayneh
Thought experiment - Some numbers.

Assume: a 223 bullet going 3000 ft/sec. The typical bullet length is .75 inches long.

3000 ft/sec times 12 = 36000 inches/sec. This equals 27.78 microsecond/inch. 27.78 us times .75 inches = 20.8 microseconds.

20.8 microseconds is how long the 223 bullet is in contact with the paper.

20.8 uS implies a frequency domain of 24,000 Hz (reciprocal of (2 X 20.8uS))

Paper (cellulose) is used for sound absorption. It has the lowest sound transmissiblity of any building material, twice as good as fiberglass. (Consensus from several web sites.)

It's getting late.

 

If an infra-light source were positioned behind the target, off to the side so it doesn't get shot, and aiming at the back of the target at an angle. A detector focused on the front of the target, on-axis with the source, should see a definite and significant step in intensity every time a new hole is made.

 

But all this still begs the question, is a 'hit' on the surrounding paper what a shooter is looking to get to test or improve his/her skills. Usually a target is bigger than the actual 'scored' area of the target. Why encourage a shooter to miss the bullseye just to move the target? Seems counter productive to any training. Usually a hit outside the scored area of a target is called a miss.