Motion Sensor Commode Lid STEP

I need a compact, plastic commode lid that lifts automatically when a user approaches. The trigger must be a motion-sensor mechanism—no foot pedals or remote controls. A clean, manufacturable design is all that is required at this stage, delivered as a single, well-organized .STEP file.

Key points to keep in mind
• Primary material: plastic, with practical wall thicknesses and draft angles suitable for injection-moulding.
• Motion sensor integration: leave space and mounting features for a small off-the-shelf IR sensor and a low-torque motor or servo of similar size. Exact components can be proposed by you, but the cavity should be easy to modify later.
• Simple assembly: screws or snap-fits preferred; minimise loose parts.
• Compact profile: when closed, the lid should sit flush on a standard round toilet seat.

Deliverable
– A complete 3D model (.STEP) showing lid, hinge assembly and sensor housing, ready for prototyping.

To help me choose quickly, please attach or link to past work that shows similar mechanism design, plastic part modelling or motion-sensor integration. A concise note explaining how you would tackle the hinge and sensor placement is welcome, but no full proposal is necessary.

This is a tiny fixed-price task, so a focused, production-ready file is all that’s needed.