AVR-Chat

Since every wacky idea is being offered:
Use an accelerometer in the cannon itself to measure recoil
momentum.  If the mass of the projectile is known, then the
exiting velocity is also known.
Ken

At 09:21 AM 3/11/2004 +0800, you wrote:
>On Thursday 11 March 2004 01:05, Dave VanHorn wrote:
>> >So you see, the biggest problem in accuracy is to positionning
>> >exactly the sensors.
>> >Far distance between the sensors, better accuracy.
>
>> Matching the optos will also be a problem. They aren't known for
>> speed either, though that's solveable.
>
>> Breaking tensioned wires might be a lot easier and more repeatable.
>
>Erm... no ... not unless you're drawing your own wires or carefully
>selecting the wires from a large spool. A few percent difference in
>wire diameter "dramatically" changes its physical strength.
>
>An old photography trick is to stick a microphone on a playing card;
>with the microphone hooked up to an amplifier with the gain set to a
>"critical" level in order to set off an electronic flash; then fire
>the bullet through the card.
>
>Of course it's useless doing that if you want to measure the speed
>of the bullet because you slow it down by piercing the card.
>
>I've thought of using a soap bubble instead; triggering when the
>refraction through or reflection from the bubble changes. 
>
>Make sure that the air isn't moving too much around the test
>cell to avoid false triggers.
>
>-- 
>/"\ Bernd Felsche - Innovative Reckoning, Perth, Western Australia
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