Magswitch MLAY 600 Lifting Magnet #8100089 outperorms other magnetice lifters on thinner materials. Buy welding supplies online at the best prices from Welders Supply.
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These are the commoner style, capable of lifting up to several tons:
In the case of the video, only a relay contact needed to be closed to open the remote lock. This problem is easily eliminated by using a transistor or MOSFET to operate the remote solenoid. Some locks use a relay to trip an internal solenoid. Two weak spots in that arrangement.
Where a solenoid is used, care in materials selection (e.g., steel surrounding the solenoid) could reduce or eliminate this method of defeating the lock. Alternatively, two solenoids (or a solenoid and a spring-loaded steel lin) might be used, arranged such that moving a magnet releases one as it pulls the other to keep the lock secure.