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Build a Palm-Sized POV TV with a Raspberry Pi Pico

Clear a corner of your workbench and gather a handful of parts, because this palm-sized television is an afternoon build, not a semester project. Here is the shopping list for a Scanwheel of your own: A Raspberry Pi Pico to run the show An A4988 stepper driver A 21-02485 stepper motor (or a similar small NEMA-style unit) Five LEDs, plus current-limiting resistors A 3D-printed case and spinning disk The Scanwheel, built by a maker who goes by [Ancient], is a mechanical TV that fits in your hand. Instead of a glowing panel, it leans on persistence of vision: your eye holds each flash of light for a fraction of a second, so a row of blinking LEDs seen through a moving slit reads as a solid picture. Spin the disk fast enough and the flicker melts into an image. How the picture actually forms The disk sitting on top of the case carries 20 small holes spaced evenly around its edge, each drilled at a slightly different height. As the motor turns, only one hole passes in front of the LEDs at a time, so light escapes in a scanning line rather than a wash. The Pico drives the stepper up to roughly 900 RPM through the A4988, then fires the LEDs in a precise order timed to the disk position. Get that timing right and the holes trace out a grid. The payoff is a 20x20 pixel color display in the center, flanked by two more 20x20 black-and-white panels that can each show a different image. Five LEDs feed all three. The whole coordination job lives on the Pico's GPIO pins, which is why the wiring stays simple enough to manage on a breadboard before you commit anything to a soldered protoboard. Small light baffles in the base keep the LEDs from bleeding into each other, a detail worth copying if your first image looks smeared. Give it a spin The full build guide, firmware, and disk files are on the project's GitHub repository , so you can match the hole spacing and LED timing exactly. If your image drifts or tears, start by trimming the RPM and re-checking when each LED switches rela

2026-07-27 原文 →
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Deep Learning & Computer Vision in Web Diffing: Solving Layout Shifts with Neural Embeddings and SSIM

When engineers talk about visual regression or website change monitoring, pixel-level diffing algorithms (like pixelmatch or Euclidean RGB distance) are usually the default solution. However, in real-world web environments, pixel-by-pixel comparisons fundamentally fail under normal user interactions and dynamic rendering conditions: Elastic Layout Shifts: A single 20px dynamic banner inserted at the top of a page pushes every subsequent DOM element down, causing 100% of the downstream pixels to fail a pixelmatch test, even if the content itself hasn't changed. Sub-Pixel Anti-Aliasing Jitter: Operating systems (macOS vs. Linux vs. Windows) render font glyphs with subtle sub-pixel anti-aliasing variations, creating thousands of false-positive pixel deltas. Semantic vs. Cosmetic Changes: Changing a single word in a paragraph should trigger a localized alert, but a minor color gradient shift in a hero image shouldn't trigger an emergency notification. At PageWatch.tech , we solved this by combining classical Structural Similarity (SSIM) , ORB Feature Alignment , and Siamese Neural Networks (SNN) for latent-space semantic comparison. In this article, I will dive into the mathematics, neural network architectures, and TypeScript implementation of our computer vision diff pipeline. 🧮 1. Beyond Pixel Comparison: Structural Similarity Index (SSIM) Unlike raw Mean Squared Error (MSE), SSIM measures visual change based on human perception across three dimensions: Luminance , Contrast , and Structure . Mathematically, the SSIM between two image windows $x$ and $y$ is defined as: $$\text{SSIM}(x, y) = \frac{(2\mu_x\mu_y + C_1)(2\sigma_{xy} + C_2)}{(\mu_x^2 + \mu_y^2 + C_1)(\sigma_x^2 + \sigma_y^2 + C_2)}$$ Where: $\mu_x, \mu_y$ are the local pixel mean intensities. $\sigma_x^2, \sigma_y^2$ are the local variances. $\sigma_{xy}$ is the covariance between $x$ and $y$. $C_1, C_2$ are stabilization constants. TypeScript Implementation of SSIM Window Sliding Below is a snippet of how

2026-07-23 原文 →
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A Hands-On Guide to kalbee: Your First Kalman Filter (and Beyond)

Everything you need to go from pip install to a working multi-object tracker, one runnable snippet at a time. kalbee is a Python library for state estimation — the art of recovering a clean signal (position, velocity, temperature, whatever you're measuring) from noisy sensor data. This guide walks through it from the ground up. Every code block runs as-is; copy them into a file and follow along. Install pip install kalbee The only runtime dependencies are NumPy and SciPy. Optional extras add object-detection ( pip install "kalbee[yolo]" ) and plotting ( pip install "kalbee[viz]" ) support. The one idea you need: predict and update Every filter in kalbee works the same way. You alternate between two steps: predict() — advance the state forward in time using a motion model ("where do I think the object is now?"). update(z) — correct that prediction with a new measurement z ("what does the sensor actually say?"). The filter tracks two things: the state x (your best estimate) and the covariance P (how uncertain that estimate is). You read them back via kf.x and kf.P . Your first filter Let's track an object moving at roughly constant velocity, measuring only its (noisy) position. Instead of hand-building matrices, we use kalbee's ready-made models : import numpy as np from kalbee import KalmanFilter , rmse from kalbee.models import constant_velocity , position_measurement_model dt = 1.0 # Motion model: state is [position, velocity] F , Q = constant_velocity ( dt = dt , process_var = 0.01 , n_dims = 1 ) # Measurement model: we observe position only, with noise variance 4.0 H , R = position_measurement_model ( order = 1 , n_dims = 1 , measurement_var = 4.0 ) # Simulate a noisy trajectory rng = np . random . default_rng ( 0 ) pos , vel = 0.0 , 1.0 truths , measurements = [], [] for _ in range ( 50 ): pos += vel * dt truths . append ( pos ) measurements . append ( pos + rng . standard_normal () * 2.0 ) # std 2.0 -> var 4.0 # Create the filter: start at zero with high uncert

2026-07-19 原文 →