electronic air-rifle target

[nirajt]

i am trying to make an electronic target for air-rifle shooting contests. the circular target is to have an approximate diameter of 1.5 inches with 10 equidistant rings inside it. each ring is a disinct score.
my main problem is a low cost sensor for the application.
kindly advice.

 

[Roff]

Since no one else is answering, I'll throw out my idea. Use concentric rings of piezoelectric film, covered with a compliant layer to absorb most of the energy. Wire each ring to a comparator, and connect your scoring logic to the outputs of the comparators.
You would probably need to die-cut the rings to get them concentric and consistent. Also have a look at United States Patent 4883271.

 

[motion]

Around in the early 1990's, I designed an electronic detector for a practice target for a crossbows. The target consisted of concentric rubber rings behind a dense mat of fiber. The mat slows down the arrows impacting the target. Since the rings are acoustically isolated from each other, the impact shock will only propagate within a ring and so I can detect which ring the arrow has impacted on.

On the rubber rings, I used cheap piezoelectric speakers/buzzers to detect the impact, each ring having 1-4 tranducers. If using piezolectric transducers will infringe on patent 4883271, you may have to use a different shock sensor.

You may also use concentric metal rings instead of rubber. Sound will propagate better on metal. This will allow you to use only one sensor per ring.

 

[stevez]

Got to wonder if a plate of some relatively uniform material and three sensors spaced well outside the outer ring couldn't be use - with time to calculate the position of the hit based on the time of arrival at each sensor. The sensors might be relatively inexpensive - the challenge would be in calculating position.

 

[motion]

Got to wonder if a plate of some relatively uniform material and three sensors spaced well outside the outer ring couldn't be use - with time to calculate the position of the hit based on the time of arrival at each sensor. The sensors might be relatively inexpensive - the challenge would be in calculating position.

Well if you use the same touch pad technology found in notebooks, it might just work. They are common enough which might lower the cost to acceptability.

 

[justDIY]

i am trying to make an electronic target for air-rifle shooting contests. the circular target is to have an approximate diameter of 1.5 inches with 10 equidistant rings inside it. each ring is a disinct score.
my main problem is a low cost sensor for the application.
kindly advice.

how about aluminum foil and tissue paper

first cut a sheet of tissue paper and foil the maximum size of your target.

now cut rings out of your foil, the more accurate you cut them, the closer you can space the rings, without them touching

then make a sandwich with your rings and the tissue paper, use as little glue as possible, since it'll make the target too stiff

idea is, as the projectile impacts the target, it will 'blow through' the thin foil and paper, and cause the ring to short to the large foil backplane. each ring could be connected to some sort of indicator, a counter or a microcontroller (whatever you feel like). and the large foil backplane could just be ground or a postive supply rail or whatever.

the targets should be really cheap to make, other than the cost of your time to assemble them. maybe you've know some little kids that can help you with your 'craft project' cutting out the rings

the target could be made to last a while by using high voltage or high current, so that the small amount of foil that makes contact is burned away when it shorts, so the short only lasts briefly enough to register on the counter, before going 'open'

 

[stevez]

Take Ron's idea and adjust it slightly - two metal rings separated by insulator resulting in a capacitor. On impact I'd expect a momentary shift in the value of the capacitor. There might need to be some logic to deal with hitting in between the rings which would result in two outputs. The rings would need to be substantial enough to withstand the hits of projectiles.

 

[Roff]

Take Ron's idea and adjust it slightly - two metal rings separated by insulator resulting in a capacitor. On impact I'd expect a momentary shift in the value of the capacitor. There might need to be some logic to deal with hitting in between the rings which would result in two outputs. The rings would need to be substantial enough to withstand the hits of projectiles.

Good idea - and the back doesn't need to be rings - it can be a metal plate connected to circuit GND.

 

[Someone Electro]

But it would be dificult to detect such an small resitance change and to prevent false trigering.

The far far easiest way i see is an piezo or somthing.Meaby you could use an magnet in a coil techneak to detect the hit.

 

[Roff]

But it would be dificult to detect such an small resitance change and to prevent false trigering.

The far far easiest way i see is an piezo or somthing.Meaby you could use an magnet in a coil techneak to detect the hit.

It's not a resistance change, it's a capacitance change, but you could be correct. I think success would depend on the mechanical compliance of the dielectric, as well as the proficiency of the designer. :roll: