I have a fan-like setup where a 4 mm-thick rod is attached to a small motor-driven shaft (also 4 mm thick) such that the rod turns about its centre as the shaft turns:
It's a closing mechanism for a catflap. It normally can rotate in both directions, but when late at night, it should lock the outward direction but allow the inward direction.
The flap's right rail slides over the rod so when the rod rotates, the flap opens up. The flap's other rail slides over a similar rod, but is connected to a bearing instead. Here's a rough sketch:
How can I block the shaft from rotating further clockwise (or the rod, for that matter) regardless of the current position? I'm hoping to have the shaft/rod blocked (using another motor) so that it won't rotate by +5 degrees or so even under some 7 kg-cm torque.