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### Topic: Shooting cinema for air rifles (Read 904 times)previous topic - next topic

#### bzeidler

##### Nov 29, 2007, 10:48 am
Hi all,
at first i want to thank the Arduino team for developing this great little board!
My current project is a shooting cinema for air rifles and pistols.

What does that mean?
A picture or movie is projected by a PC to a surface of approx. 1.5 square meters in size.
When shooting at any prjected target, the bullet impact is measured and located.
I use an arduino diecimila for that.

How does it work?
I use 4 microphones located in the corners of the surface. With 4 amplifiers and comparators
the sound of the bullet impact reaches the microphones within a different time - sound is moving
with approx. 340 meters per second.
The time difference is measured and based on this the position is calculated.
In addition, there is an I2C temperature measurement chip to caltulate the exact speed of sound.

How accurate is it?
Currently i get an average accuracy of less than 1.4 mm, which means the calculated position is
only 1.4 mm away from the real point of impact. This is far enough for moving targets.

How does it work technically?
I use the Timer1 with a rate of 2 MHz (divider=8) to measure the time. This gives a timer/distance
resolution of approx 0.2 mm! On the current prototype, the maximum time measured is about 5.3 ms.
With all the floating point math within the position calculation there are only 300 bytes
left free in the Flash memory!

Do even very timing-critical work can be done with an arduino!!!

Regards,
Bernhard

#### kuuk

#1
##### Nov 30, 2007, 04:27 pm
only a question of time until http://www.darpa.mil will call for an arduino grand challenge...well...
is there a video of it? i once considered this concept to get a position, but never imagined it could be at least similar precise.
kuk

#### bzeidler

#2
##### Dec 01, 2007, 02:38 pm
Currently i'm working with a small prototype.
The big one is being built, i have to prepare some stuff for the large projection wall.
The last thing i made was laminating 2 square meters of aramide with epoxy to
have a "bullet-catcher" behind the surface. Now i have to wait until the epoxy
is hardened...
When it will be working, i will post some videos & pictures of it...

#### zuckerman

#3
##### Apr 14, 2010, 04:14 pm
Howdy, has there been any activity on this project, or is it dead?

#### bzeidler

#4
##### Apr 14, 2010, 07:20 pm
Yes, there was a lot of activity.
In the meantime it is a complete product: www.aircine.de
I dont use Arduinos anymore (but i did for a while!), now the
complete arduino schematic is included into the PCB. And i dont
use the ATmega timers anymore for measuring. It works, but
i developed a CPLD and now the measuring is done completely in
hardware. Measurement accuracy of the hardware now is better than
0.5 mm...

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