NicaDrone OpenGrab EPM v3Overview

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 475 V.

A thyristor bridge is used to discharge the capacitor in either direction through the winding inside the AlNiCo material. This results in a short, 20 us 300 A pulse creating a 100 kAm 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 operating principle is available on Wikipedia.

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

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

˃˃˃ Applications

Cargo lifting in UAV and robotic applications.

Robot workholding.

Education, demonstration of magnetic properties.

Features

Steady state power under 50 mW

Short cycle time

˃˃˃ Documentaion / Links

Source repository (firmware sources, drawings, etc)

https://github.com/Zubax/opengrab_epm_v3

PCB layout and schematic

https://upverter.com/ctech4285/1dada3422c772add/OpenGrab-EPM-V3R3/

Purchase from NicaDrone

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

Documentation

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