[Gdeaver]

The control algorithm for firing an ejection charge at a specific altitude is a very complicated thing. If you go down this path you may spend all your development time on the electronics and get nowhere. I would suggest you get a copy of a rocketry design program called ROCSIM and work on the rocket design - engine choice - simulation to build a rocket that by design reaches your goal altitude. Once you get the rocket built you can dial in the altitude by weight. If there is still time and you wanted to add electronics I would suggest a simple timer. There are devices called G-switches that can Trip the start of the timing. An ejection charge is the best way of popping the parachute. This involves the use of 4f black powder or pyrodex. You must be 21 to purchase and use these. A low current e-match is usually used to initiate the ejection charge. You need a low explosive licence for these. I would suggest that you try and track down a NAR or Tripoli rocket club member in your area to mentor you on these parts. I think you will find most members very willing to help. You may also want to visit a high power rocket launch. Just being there and watching is impressive. Remember unlike first robotics, rocketry is more critical engineering. If you make a little mistake you usually end up with expensive confetti