Ancient lock gets smart

A NodeMCU (ESP8266) paired with a DRV8833 Dual MOSFET H-Bridge comfortably drives the DC motor

This is the last iteration of the motor mount / enclosure:

After some time abandoned, the lock had the pulley installed but no motor. I just finished the enclosure for the motor, ready to 3d-print!

When I was testing the idea, I thought I could use the original cylinder with the key in it, like on the retrofit kits. I got to learn the hard way that a pin tumbler lock does not operate well under the axial load of a belt. Nuki and other systems that work with the original key are mounted on top of the lock and avoid this, but I wanted to keep the contraption as flat as possible, since this is a rim lock and it's already bulky.

I then partially copied the lock in CAD, on top of which I designed a mounting plate to fit two small bearings and support the short axle for the belt pulley and actuating cam.

Got this printed this with PETG (because it turned out that's what my brother had in the printer at the moment). Feels really solid, especially when assembled. The bearings press-fit nicely, lucky me.

This lock does not actuate the latch from the inside, it makes no sense since it has a dedicated plunger for that. After considering actuating the plunger electrically, I decided it was easier to modify the internal latch mechanism to operate from the inside in the same way it operates from the outside.

I riveted a screw into this lever arm so it is reachable by the inner side cam. The lever is normally only operated by the front side cam, not on the picture. Both inner and outer lock cylinders are coaxial.

I am now in the process of designing and printing a motor mount/box and associated electronics.