this is a parachute release mechanism for a model rocket, i built it for a water rocket but other types would work. It uses an Arduino pro mini (http://www.sparkfun.com/products/9218) which is really good for this as it weighs less than two grams and is tiny. The mechanism fits in a 2 litre drinks bottle which can be attached to the top of your rocket, you could easily scale this project up or down for different sized rockets.

the device works with a tilt sensor, when the rockets power tails of then it will tip forward as the front is heavier, this will (hopefully) trigger the tilt sensor which will turn the servo releasing the door .

What you'll need:
Arduino Pro mini (or a full sized one would work fine)
batteries +holder
micro servo

tilt sensor http://www.oomlout.co.uk/tilt-switch-p-243.html?zenid=b02b94c613289937d7d01f66b4264578
plastic bottle
elastic band

masking tape
soldering stuff
pliers and wire clippers
FTDI breakout board( to program the arduino)

Step 1: Making the Frame

the frame that holds the parachute is made out of cardboard, i drew around the bottom of the bottle and cut it ouut then used it as a template for the other side. i also cut a long piece of card slightly thinner than the diameter of the circle and cut a rectangular hole in the middle of it for the servo. Push the servo through this hole and screw the screws into the card. I used superglue to attach the two cardboard circles to the strip (like in the picture).
i cut out four cardboard triangles to support the circles and glued them in place. i made a flap that goes over the servo to protect it from the parachute and made two boxes of card for it to rest on and glued a bath sponge cut in half to the flap, this is so that when the door on the bottle opens then the parachute is pushed out.
Really nice! You could try adding a shock cord to your parachute and a buzzer that screams after it deploys to help you find it, if your rocket goes high enought to justify it. I've lost so many rockets...
the buzzer is a really good idea, i will try that
GPS would be equally cool, maybe getting too high on the weight side of things though especially since you have to actually transmit the location which would require quite the amount of energy, then again, if you were looking for something already landed you'd only need it to call it's location once and transmit locally, so if you were working with bluetooth or Wifi you could use that as basically a tracker so as soon as it comes within range you could connect and have it send you it's co-ordinates, it wouldn't even have to process the GPS data, you could have it send you it's raw location data and you process it from a phone, tablet or laptop when you're looking. <br> <br> <br>Orr, you could just not lose the damn thing., though I know that can be kind of difficult.
Good stuff, thanks for sharing.

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