The ZeptoMag is an electronic device which detects when a rocket turns over at apogee and fires the ejection charge. It can also deploy based on a timer starting at launch detect.

Features

• Detects when the rocket turns over at apogee by measuring the Earths magnetic field.
• 2 high current (5A) pyro channels.
• Fires one pyro channel at apogee.
• Fires second pyro channel as backup for the first or as set by a timer.
• Accelerometer for launch detect, prevents pyro channels from firing when handling the rocket and starts timer at launch.
• On-board LED will turn on when the ZeptoMag is pointing below the horizon. Makes it easy to verify correct operation.
• Easy calibration function. Hold the board at the angle you wish to deploy and press the button. Allows adjusting for different magnetic fields worldwide and choosing the angle you wish to deply at.
• Magnetic sensor resets several times per second to avoid errors from temporary exposure to magnetic fields.
• Small size: 39.4 x 12.7mm (1.55×0.5″) If the wires to the battery and ejection charges are soldered directly to the board it will fit inside a 13mm ID tube (BT-5), if screw terminals are used it will fit inside a 18mm tube.
• Capacitor to supply power in case of momentary loss of power during flight or drop in battery voltage when firing the pyro channels.
• Can be used with 3-13V batteries.
• With two 2.3mm mounting holes for #2 or M2 screws.

ZeptoMag User manual (PDF)
Some videos of the ZeptoMag in use on YouTube

This version is with screw terminals. It is also available without screw terminals.