Lewin Day's Mercedes Gets an Espressif ESP32 Upgrade for Pixar-Style "Angry Eyebrows"

Self-described "madcap engineer" Lewin Day has brought a little expressiveness out of Pixar's imagination and onto the road, modifying a real car to have "angry eyebrows" tied to how hard you push the gas pedal.

"This was a really fun build," Day says of the project, which was inspired by a joke post seen on Twitter. "I started with an Arduino Uno but went to the [Espressif] ESP32 when I needed more clock cycles to drive the WS2812Bs [LEDs]. In essence, though, they were a bit overkill given I just wanted to change the color of the entire eyebrow at once."

Those eyebrows are, naturally and logically enough when you accept the central premise of "I want my car to be able to express emotion," mounted above the headlights of a Mercedes W210 E-Class. Eschewing tying the project directly into the vehicle's CAN bus, Day reads the vehicle's throttle position directly through the microcontroller's analog to digital converter (ADC) — and adjusts the angle and color of the motorized plastic-ruler eyebrows according to exactly how hard the driver is accelerating.

"[I] also did some pulse timing to read RPM [revolutions per minute]," Day explains. "Higher RPM or throttle position = car goes grr! There's so much more you can do with this — you could have the eyebrows doing different wiggles left and right, you could even have them jumping up and down to do, like, you know, a little cheeky raised-eyebrow Milhouse [Van Houten, from The Simpsons] kind of thing."

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