Build a DIY Dasai Mochi with an Animated LEGO Minifig LCD Face
Upir's new DIY Dasai Mochi is super compact and can display cool faces designed to mimic LEGO minifigs.
Have you seen the Dasai Mochi? It is a cute little car “companion” gadget that sticks to your dashboard. It lights up and displays different expressions on its LCD face as it reacts to your driving. It is a JDM trend that is popular right now and Vaclav Krejci, AKA “upir,” has been working on making his own DIY version. His newest iteration of the DIY Dasai Mochi is super compact and can display cool faces designed to mimic LEGO minifigs.
If you didn’t see Krejci’s first video about his DIY Dasai Mochi project from last year, you may want to start with that. But the new video provides enough background context that it can stand alone.
The big updates here are a reduction in size and the LEGO graphics. This new version is significantly smaller than the first and smaller than the official Dasai Mochi devices. Krejci would have liked to make it as small as an actual LEGO minifig head, but couldn’t find a screen that was a suitable size. So, he settled for more of a LEGO Duplo scale.
To get the device down to the size, Krejci had to make some sacrifices. The most obvious of those is that only the screen itself, a Waveshare 0.85” 128×128 full-color LCD, fits inside the helmet. The hardware to drive that LCD, a Seeed Studio XIAO ESP32-S3 MDB (Microcontroller Development Board), is external. If you were using this in a car like a Dasai Mochi, you would probably tuck that under the dash somewhere and hide the wires going to the helmet.
The helmet is 3D-printed and now we’ve covered all of the important physical bits. But what is particularly interesting is the way Krejci rendered the LEGO minifig faces.
To do that, Krejci used the amazing BrickLink Studio software. That is 3D software that lets you use bricks from LEGO’s entire historical catalog to build virtual models. It also produces pretty nice renders. Krejci was able to take advantage of that to capture very clean images of all the LEGO heads and faces he wanted. He was also able to get that helmet 3D model from the same software.
From there, it was a simple matter of downscaling the images to an appropriate resolution and using them in the code for the XIAO ESP32-S3, programmed in the Arduino IDE. At this time, it just displays those images. But it would certainly be possible to replicate the full Dasai Mochi functionality.