166: Capacitive Button Guides

We have a desk lamp in the bedroom that uses capacitive buttons, the kind of non-buttony button that you can’t actually feel. Like the PlayStation 3 power button, there’s no physical feedback for touching the right area or pressing it hard enough to activate. Instead, you just brush your finger against the region and bam, the lamp turns on.

The problem we’ve run into is that when the lamp is off, you can’t see the tiny, half-inch circle that you must precisely tap on the 7 inch base. You just kind of stab at the thing with your finger until you hit the target, and hope you don’t brush the other buttons on your way by. This lamp’s secondary buttons are the same half-inch circles, spaced about an inch from the power button, and they control light temperature and a sleep timer.

These buttons have no texture to them at all, so it’s impossible to aim for that power button in pitch black.

We’ve dealt with this problem by ignoring it for at least a few years now, but there’s a new wrinkle in our lives that is helping us understand the importance of quick physical feedback in pitch black darkness. She’s about two months old now, and when she starts crying we don’t have time to jab at the lamp base until we get lucky.

Well, I’ve got a laser and some thin sticker material on hand, and all it would take is a little texture somewhere on the base to help the blind finger find its way. Imagine the seconds of frustration saved!

I used a strip of the sticker material to determine how it affected the functionality of these capacitive buttons

A small scrap of the laserable sticker material was used early on to figure out how the capacitive regions would be affected by the sticker itself. I reasonably expected that if I covered a button entirely it wouldn’t respond to a tap with a finger, but it was worse than expected! If I covered even a tiny sliver of one of the button’s active regions, it would prevent that button from working at all. In some tests the sticker wasn’t even overlapping the small smooth graphics that mark each capacitive region, but the proximity was preventing functionality. So I knew that I would have to carve those areas out of the sticker, no matter what shape it ended up being.

The lamp base layout in Illustrator. Prototype on the left, final on the right.

I laid out the lamp base and its capacitive button areas, and made a sticker shape that followed the edge of the base on the bottom. I mirrored that curve on top, creating a football shape, and I filled it with a sunburst design. The idea was that these engraved lines would trace back to the power button, guiding the finger. In practice, the pattern was too fine to really identify which direction the lines were going.

The prototype was too large and loud a design, and my initial measurement was off a hair on the side buttons

The engraving was too stark, too high contrast, and not as functional as I’d hoped. The football shape gave me the impression of Stewie Griffin screaming into the void. The OttLite logo could be covered, for all I care, but not half-covered, so that’d be fixed too. A second design was much smaller, with much thinner lines engraved on the surface.

The final sticker doesn’t cover any of the buttons’ active regions, and doesn’t look like Stewie Griffin’s head

The finished piece is easy to navigate in the pitch black bedroom—mission accomplished! Thankfully, it’s also much more eye-pleasing than the prototype. One of the benefits of OttLite’s capacitive button solution here is that the lamp base has a clean, minimal look. This aesthetic is going to be damaged no matter what you add to it just by adding to it. That’s still true here with the grey circle breaking up that smooth white surface, but it hides itself well between the printed graphics and logo, keeping the addition understated.

More importantly, when it’s time to get up and tend to our newishborn, no more precious patience is burned on a stingy lamp button.