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