I recently built a synthesizer module which needed 8 vactrols. It can be difficult and expensive to source reliable vactrols so I decided to make my own from from flat-topped LEDs and LDRs. In particular, the use of a flat-topped 5mm LED allows the assembled vactrol to fit within the footprint of a VTL5C vactrol in KiCad.

The excellent Vactrol housing by pnoreck was a great starting point but needed a bit of tweaking for my needs, so I

• reduced the length to work with a flat-topped LED with the LED & LDR touching when the housing is assembled
• reduced the gap between inner and outer sections for a tighter fit when printed on my Ender 3
• reduced the size of the holes for the LED & LDR leads
• adjusted the spacing of the LDR lead holes
• added a 'polarizing bevel' to match the KiCad footprint

I've also included a custom KiCad footprint (Custom_vactrol.kicad_mod) with slightly larger holes and improved lead spacing compared with the default component, and also a 3D model (vactrolModel.step) for use in Kicad.

Added 13-09-23 - vactrol-housing_LH.stl and vactrol inner_LH.stl have 10% larger holes for the LED/LCD leads, with a flare on the inside to make it easier to insert the components if you have trouble with the original housings.