After trawling many companies I ended back on the Tech supplies website, their own solenoid had been out of stock for weeks but no more! I have ordered and received a miniature, PCB mountable ‘pull’ solenoid.

First thing to do is to test it connected to my board… and it works! (I seem to be getting used to things working first time, this may mean that my board is trying to lull me into a false sense of security…) The 4.5 v is enough to pull the bar in. Now I need to design and etch a small board to support it in inside the safe door:

Now that The board is finished I need to fit the spring to force the return (one butchered ball point later), oh look a small spring ;). To give the bolt more bulk and to stop the spring falling off I have fixed a nut on to the end as you can see below: