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Blinded by the Light

Over on TheRPF.com, a user named simply ‘stan’ shared some interesting numbers – measurements, apparently, for the screen-used Voight-Kampff prop?

I don’t know where these dimensions actually came from, as stan’s responses have been a bit cryptic, but these numbers are fairly close to what I’ve got at the moment. By way of example, my overall height is ~115mm, versus 111.87mm; thickness of lower portion is 19.05mm versus 18.98; popout section dimensions are a near match at 15mm x 20mm. My “nonfunc lens diameter” is closer to 9mm, but you may have been measuring the literal lens, while mine is the lens plus outer bezel.

All things considered, I’m going to take the fact that my dimensions are a near match for these mystery numbers as an indication that I’ve been able to peg the size almost exactly… which is good, because I finally had a bit more time to actually get some work done.

I spent ages digging through Mouser and Digikey trying to see if the LED mounted on the front of the metal rails (pictured above) was an actual part. Based on my measured dimensions, I was filtering by looking for any optoelectronics that had a roughly 8mm x 8mm footprint (plus or minus a few mm) and emitted blue light. I ultimately couldn’t find exactly what I was after, so my next thought was to use one a smaller, ultra-bright surface mount LED and simply design a ‘shell’ that fit around and over it to make it look the part.

I found a few interesting LED options for this purpose: XPEBBL-L1-0000-00201XPCBLU-L1-0000-00W02, and GB CS8PM1.13-HXHY-35. These LEDs are all small square packages with lens assemblies attached which increases their overall viewable angle. They are also rated for stupid high levels of brightness. Two of them are 3.5mm x 3.5mm, while one is 3mm x 3mm. The 3.5mm size is what I based my initial 3D placeholder model around – the small LED pictured above.

Of the three LED options I picked… well, they all ended up having issues. They are tiny, run easily off 3V, and emit a bright blue color. That said, they are unbelievably bright. Like, damage-your-eyes if you look at it for too long bright. They also get super hot in about 3 to 4 seconds of use – so hot that one of them actually melted my solder-tinned 3V test wires to the back of the LED after a few seconds. Got a few burned fingertips while I was trying to snap these photos.

These characteristics are not great in what should be a user-friendly prop. I’m thinking at this point that I may opt for a much friendlier 3mm through-hole discrete LED option. It won’t be as ludicrously bright, but they’d also be easier to source and a lot less dangerous. Conveniently, the shroud I modeled also fits around one of those.

I also traced the outlines of the metal pop-out frame as closely as I could from the images. I’m not entirely certain about the relative thicknesses of the parts yet, but I wanted the middle frame to be on the wider side so that the front LED had something to mount on properly. The holes are sized for M2 (2mm) screws. As it stands, the whole thing is thin enough to slide into the body of the VK, and the LED is actually positioned just right so that it won’t interfere with the tactile switch I plan on putting into the front.

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