Rocketware

An 1:10 scale replica of the Atlas Centaur rocket from the late 1960es was my level 3 project. The Atlas was a 1.5 stage rocket, two booster motors were jetti- soned during flight. As these motors did not have their own tanks, they count only as half a stage. The scale model should mimic this behavior, so some electronics were required to ignite the booster motors when ignition of the main motor is detected and release the booster after burnout of the main motor. Two servo controlled clamps keep the booster in place.

For the certification flight without the booster motors, a quick and dirty so- lution was created based on a ATtiny microcontroller. The PWM outputs were used to control two servos, a button allowed to toggle between the two servo positions. The servo positions themselves where not configurable but hardwired in the firmware. A breakwire input triggered the timer, but the delay time wasn’t configurable either. Consequently, this timer was not usable for any other project.

Unfortunately, no single product seemed available that would be capable of handling all the requirements from one simple device. Thus the Atlas-Timer project was born. It aims to create a timer with the following characteristics.

1. Two independent pyro outputs capable of handling the high currents needed for motor igniters.
2. Both pyro outputs should be capable of measuring and displaying the resis- tance of the attached igniters.
3. Two independent servo outputs.
4. The timer should satisfy all the requirements of the safety code.
5. The timer should becompletely programmable, not only the time when pyro outputs fire or servos are switched to a different position, but also complex sequences of servo moves should be programmable.

The schematics and the source code for firmware and document are published under the GNU General Public License.

Download links:

• Atlas-Timer manual
• Complete source code of version 1.1