I put two throttle-driven eyebrows on my car.  Now he looks angry when I knock on him

I put two throttle-driven eyebrows on my car. Now he looks angry when I knock on him

Oftentimes, we think of cars as having faces. Regardless of the movie cars You might believe, headlights are the eyes. Cars like the Jeep Wrangler that have round headlights add to the effect. You may have seen the “angry eye” combos that make these vehicles look crazy with plastic slashes – but it seems a shame that the car is limited to one emotion. Fortunately, I found a way to give eyebrows that actually move, and tested it for you on my two Mercedes.

A man named Peter On Twitter, Jeeps had the idea that Jeeps should have eye shutters that move relative to throttle position. The lower the accelerator pedal, the more powerful the car. That sounded so funny I simply had to build it myself.

I didn’t have any components on hand, nor did I have a Jeep Wrangler. However, I had a file Mercedes E-class With decent round headlights, I thought that was close enough to start. I dropped a few hundred dollars on parts and started working.

The resulting building was a perfect expression of my creativity and happiness. It may not be street legal, or even in good taste, but I promise you, it’s a lot of fun.

operating theory

With so much experience in electronics, it didn’t take long to come up with a concept together. All I needed was a microcontroller to read the car’s throttle position, then use it to drive the angle of a pair of servo motors. The servo motors will be installed at the top of the headlights, and they will move the eyebrows accordingly.

It didn’t take long to get a proof of concept up and running on the bench.

Early build of my proof of concept. The red circle is a microcontroller board that controls the system. It reads “throttle position,” which is simulated here with the knob on the right. Based on that, he directs the machines to rotate the eyebrows on the face of this charming cartoon character. loen day

Desiring a quick and easy build, I lent the components I was familiar with. I grabbed some basic servos, an Arduino Uno microcontroller, and some supporting components, and started putting all the electronics together. Unlike Peter’s design, I wouldn’t use precision roller shutters. Instead, I’d choose suitable angry cartoon eyebrows.

The first thing I had to figure out was how to read the throttle position. One way is to get messages from a file can bus related to the throttle position. This will work on a variety of modern cars, although it is a bit complicated on my 1998 E. Instead, I went for a simpler method, and decided to read the variable voltage directly from the throttle position sensor under the hood.

The Arduino then takes that effort and, as it varies, asks the machines to move the eyebrows. I set up the system so the brows are a little relaxed at idle, then quickly shift to a more aggressive angle when the throttle is on.

With the help of some shower curtain rails to act as mounting and brow panels, I had a basic system up and running relatively quickly. Leaning on the throttle would make the car look grumpy, just as I had hoped.

There were some problems, though. car sounds Furious based on rpm. However, my system only a look Angry when using the accelerator pedal. If you lean on the throttle, the car will look angry until you hit the red line and have to back off. I quickly realized that the system would likely perform better with the rage set to RPM rather than the throttle position.

The other problem was that the metallic eyebrows I made weren’t very visible from a distance, especially at night. I realized I could instead build custom brows that glow and glow in an angry hot red as the rage (and RPM) rose. This took a lot of extra work to make the brows constantly glow and look the part. I gathered together LED strips, clear rulers, and foam, and based my experience with lubricants and adhesives to make something that would hold up and look the part.

These changes necessitated switching to a more powerful microcontroller that could operate LEDs and devices at the same time without skipping or vibrating. I had a little time to improve, so I chose the ESP32, which runs at 240MHz and fires the Arduino Uno out of the water.

I also had to find a way to scrape the Mercedes RPM signal, which I eventually found by hacking into the wires of the crankshaft position sensor. I was well aware that I might end up piloting the ECU or my car in the process, but when you’re running fast, sometimes you just have to focus on getting the job done.


After hustling every spare minute I had, I was able to get the system working. Obviously driving with big angry red eyebrows on your car is a bit risky, so I drove off onto a secluded dirt road before I first caught my Angry Eyes. With the cam spinning, I leaned into the throttle, and made the humble V6 engine like a beast. The face of the car now showed it meant business, eyes and eyebrows glowing with all the dangerous red LED lights it could provide.

With angry eyes blazing, other motorists will see that I mean work every time I overtake during an overtaking maneuver. Whether it was blasting off on a dirt road raising dust, or darting when stopping, the eyes added drama and attitude that had been missing in my life thus far.

They also made me wish I had a bigger engine under the hood of the Merc, if I’m honest. I wanted something more suited to the car’s expression with a proper annular exhaust note.


The construction came together in a short time schedule. There was a lot of trouble with eavesdropping on the car’s electronics, and the hot temperatures under the hood and rotary engine parts weren’t friendly either. The development process also claimed the lives of several LEDs, two microcontrollers, and a servo.

Despite all these challenges, the end result worked, and it worked surprisingly well. If I wasn’t worried about the police impounding my car, I could run it all the time. If I did, I’d probably add a function to allow eyebrows to be pointers as well. LEDs can light up any color of the rainbow, and move, too, so there’s plenty of room for silly fun.

The way I designed the system, it would be very easy to port it to other cars as well. It can be easily connected to any vehicle with a simple resistive throttle position sensor, or any vehicle with an inductive crankshaft position sensor. Instead, it’s easy to reprogram to work with other signals, and you can easily modify it to read the CAN bus instead. For the interested parties, I’ll eventually be posting the build files online, but realistically, if you read this article, you’ll get the basic information you need to rebuild the project.

Should you do this for your own car? Certainly, in my eyes. This would be a great modification to any Jeep Wrangler or Mazda Miata, and it would make you laugh at the cars and the local coffee. It will most likely make you a star on the drift circuit or on the local burnout board. If you’ve got a file 240 seconds in formula d And you can flirt your way through scrutiny, let’s talk about swinging these in popups.

With that said, I wouldn’t recommend using it on the street. The flickering lights in the front of your vehicle can be distracting to other motorists, especially when they’re red. If I had a ridiculous thing permanently installed, I set it up to be simple non-moving daytime running lights unless I specifically enabled them for fun. This is about the only way you can get rid of something so ridiculous without speaking sternly from the local police.

Overall, I really enjoyed putting this build together. I’d like to send my hat to Peter for the idea, and I hope you all enjoyed the show. Let me know if you build your own – I really want to see her in a drift video!

Got a tip? Let the author know: lewin@thedrive.com

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