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Topic: tonfa, police stick measuring hits and impact (Read 1 time) previous topic - next topic

bassofsinn

hi everybody,

I want to  build a tonfa, police stick that counts how hard and how often somebody used it.
The idea is that,  if a policeman uses his gun he has to justify it, but if he hits somebody with his tonfa nobody can prove it.

As sensors i want to use these little things.


This mechanism is used in cheap bouncing balls, that start blinking if they hit a wall hard enough.
(if the kinetic force is strong enough the feder in the middle bends over and closes a circuit).


The tonfa has a diameter of 3 cm,
and ist 56 cm long.




my questions are:

Are there better impact sensors or should i use a high-g accelerometer?
How many g´s, like g-force units measures a hit?
I have a few doubts about my "sensors" that i use at the moment, the differences between the impact forces should be
detected through the different placing along the stick.
the sensor nearest to the hand only closes when the impact is realy strong.(leverage)

Which arduino would you recommend me to use? ( power, wireless, usb, size,nano, mini, pro series?)
i have to put the batteries into the stick, and there must be a communication with the computer.
either wireless or through usb.

If i want to use a switch, where should i place it and which one should i use?
Or is it able that the arduino turns himself on/off ? (sleep mode)

The sensor data ( which are at the moment digital, simple closed or not closed ) must be  stored on the arduino. (eeprom)
Perhaps somebody has a piece of code that he thinks would help me, like counting and storing multiple button signals on the arduino.

Should time play a role? ( like, when has he hit, the i have to do something like time related counting)

Code for visualizing my sensor data?

Some piece of hardware that you would recommend me?
Completey different solution?

Well if somebody has any idea, solution or answer please post it.
Im thankful for every answer.

Sincerely
johannes




bassofsinn

does anybody have any ideas or solutions.
i can´t wait to drill a hole into this thing  :)

AWOL

Quote
but if he hits somebody with his tonfa nobody can prove it

DNA analysis of the blood/hair?
Match teeth marks with dental records?

Proof of shock on a stick proves nothing - he could have been banging on a riot shield to intimidate.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

robtillaart

Quote
Proof of shock on a stick proves nothing - he could have been banging on a riot shield to intimidate.

so it needs another fast temp sensor to measure the bodyheat :)
Or the riotshield needs sensors too so matching 'bangs' cancel eachother out....

I like the concept but then for a baseball bat, hockeystick. How fast was the swing, how hard was the bal hit, could make a good exerciser.

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

bassofsinn

Quote
Proof of shock on a stick proves nothing - he could have been banging on a riot shield to intimidate.


no doubt thats right,
but my goal is not to design some kind fo law-proof device.

2010 have been a lot of demonstration in germany and next to my already mentioned concept i had the idea that the  sensor-stick
could be  part of a game for policemen in demonstrations. For every hit they get a point, they travel from demonstration to demonstration and can upload their rankings to the internet. there are then awards like " most hits in one battle", " overall winner" etc.

the concept is two sided, and the aim is to design a prototype,
an artistic gadget for an extreme enviroment,
that draws attention on the topic




i struggle with the realisation and i would be realy thankful if you could help me here,
even if you have only one or two answers to my questions, write them down, please,

see you later,
johannes

AWOL

This reminds me of a semi-live fire trainer I saw a long time ago.
The system used a barrel insert with a laser, triggered by the shock of a blank in the chamber firing.
The laser then registered on sensors on the opponents' clothes.

Problem was, when the squaddies ran out of ammo, they found that hitting the butt of their weapons with rocks or planks would cause the laser to fire, so they could carry on shooting.

The fix was to ensure the laser fired on shock and light.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

Venger

I am also new to the arduino.

But I can give you some guidance.  Starting looking for a G sensor with very high G ratings.  The end of a baton can be going very fast when it hits something, and it will stop in a few milliseconds.

This would be a good starting sensor:
http://www.sparkfun.com/products/9332

If you make the grip so that they hold it the same way each time, you might be able to get by with 2 of those or a high G 2 axis if you can't find a 3 axis( poking someone is likely not that much of a concern).

You might have to worry about the crystal oscillators, the standard ones that arduinos have might start to fail after a few hard hits.
A hard enough hit could cause the Atmega chip to reset or act strange.
Make sure all your components can survive 300gs, if not put them as close to the handle as possible.

bassofsinn

venger thank you for your advice,
this high g accelerometer is quite nice. but i cant find one with two axis.
i will try to put everything as close to the handle as possible, that´s for sure.

which kind of arduino should i use? ( wireless, usb)
and what should i use to power it up? ( which kind of battery, how to store the single batteries etc=
do i need a switch?

any idea about the code?

thank you all,
johannes

Udo Klein

Quote
2010 have been a lot of demonstration in germany and next to my already mentioned concept i had the idea that the  sensor-stick could be  part of a game for policemen in demonstrations. For every hit they get a point, they travel from demonstration to demonstration and can upload their rankings to the internet. there are then awards like " most hits in one battle", " overall winner" etc.


Is this intended as a joke or an art project? I doubt that such a game would withstand the media outrage it would create. Legal questions would arise as well.

So what is the real intention behind this project?

With regard to the technics. The hardness of the impact is determined by the force upon impact. This depends on

1) Mass of the weapon --> heavier weapon = more force
2) Speed of the weapon --> faster weapon = more force
3) Distance travelled "in the target" before target and weapon move at the same speed, harder target or target moving towards weapon --> more force

(1) is simplified though. Depending on if you stab or strike you have to consider different values for the "mass".

Furthermore the damage to the target does not depend on the force alone. It also depends on the sensitivity of the target in that areas.

Basically hitting a shield with the stick will measure very high force. But stabbing somebody will show much less accelaration/force but will cause much more harm.

I definitely wonder what and why you really want to measure and why.


Udo
Check out my experiments http://blog.blinkenlight.net

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