The LED strip lights have a reasonably diffuse pattern with an on-axis bright area that puts more light on the rear of the counter than seems strictly necessary. Revising the original brackets to tilt the strips moves the bright patch half a foot forward:
For lack of anything smarter, the angle puts the diagonal of the LED strip on the level:
The translucent block represents the strip (double-thick and double-wide), with a peg punching a hole for the threaded brass insert.
Although the source code has an option to splice the middle blocks together, it can also build them separately:
Turns out they’re easier to assemble that way; screw ’em to the strips, then screw the strips to the cabinet.
I moved the deck screw holes to the other end of the block, thus putting the strips against the inside of the cabinet face. It turns out the IR sensor responds to the DC level of the reflected light, not short-term changes, which meant the reflection from the adjacent wood blinded it to anything waved below. Adding a strip of black electrical tape killed enough of the reflected light to solve that problem:
The tape isn’t quite as far off-center as it looks, but I’m glad nobody will ever see it …
The before-and-after light patterns, as viewed on B-size metric graph paper centered on the left-hand strip and aligned with the belly side of the countertop:
Those look pretty much the same, don’t they? So much for photography as evidence for anything.
The OpenSCAD source code as a GitHub Gist: