Magnetic gate lock from Texecom PSU200XP

[daern]

1. Back EMF from the lock might upset the alarm.

I forgot to mention this one - the door lock (which came with the least useful instructions every seen!) came with a mysterious small blue electrical component. However, a bit of Googling found this page which not only explained what the impact of back EMF is with magnetic door locks, but also why a diode (which I'd have probably used myself, not knowing better) isn't a very good solution for them as it can result in the lock getting stuck, or being slow to release. Fortunately, that page mentions MOVs (metal oxide varistors) as the correct way to consume the back EMF from the coil, and even has a nice picture of the exact, mysterious component that was in my box so it solved two problems in one.

In the end, I wired it to isolate both connections to the coil through my relay (mostly as this made it much easier to locate the MOV in the panel), so I think the combination of the two should avoid any unexpected PSU zapping.

 

[sparkymarka]

It goes across the supply at the lock end

 

[daern]

It goes across the supply at the lock end

From the documentation I've been using, it says to put it at the switch end, while it would make definitely more sense to get it closer to the lock. As it happens, it's a moot point as the lock has a 6ft captive cable, so the closest you can get it is at the end of this bit of wire, which I've done.

Seems odd that they don't just stick it inside the door lock itself during manufacture and save everyone a whole load of trouble...