Electro Permanent Magnet (opengrab EPM V3 R5C) +Cable set UART UAVCAN external button, cable Pixracer, cable Pixhawk.

The OpenGrab EPM v3 is an electropermanent magnet, combining the advantages of electro and permanent magnets. The device creates a very strong magnetic contact with a ferrous  target. It supports UAVCAN, RC PWM and push button operation.

Theory of operation, The NXP LPC11C24 MCU drives a mosfet connected to a transformer in a flyback configuration to charge the main PET capacitors up to  475V. 

A thyristor bridge is used  to discharge the capacitor in either  direction though the winding inside the ALNICO material. This results in a short, 20 us 300 A pulse  creating a 100 k Am  field in the ALNICO material. this causes the magnetic domains in the ALNICO magnets to align in a particular orientation to form a magnetic circuit with a ferrous target. More detailed explanation of the operation principles is available on Wikipedia.

An ON command results in the charging the capacitors 3 times to achieve full magnetization.

An OFF command results in charging the capacitors several times with changing direction and decreasing amplitude, effectively degassing the ALNICO material.

Documentation / Links

https://github.com/Zubax/opengrab_epm_v3

PCB layout and schematic

https://tools.upverter.com/eda/#tool=pcb,designId=26435306801c5de9

Purchase from NicaDrone

http://nicadrone.com/index.php?id_product=66&controller=prod

Documentation

https://docs.zubax.com/opengrab_epm_v3#Mode_and%20status%20codes