Category Archives: Microcontroller

Building an autonomous robot car

This project is about an autonomous vehicle, based on a modified toy RC car, that can drive along a “road” without any manual interaction required.

To this end, the car’s remote control is modified so it can be attached to a microcontroller, that receives commands from a Python program running on a laptop. The camera, mounted on the top of the car, streams its view wirelessly to a neural net on the laptop, that decides what steering commands are the most appropriate at every time step/frame.

In this post, I will present how to modify the remote control (soldering and mechanical changes), how to extend the car, and how to stream live video, with low latency, from the Raspberry Pi to a laptop using GStreamer and OpenCV. An upcoming post will show a reliable neural net model for automated steering.

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3D scan with a hobby LIDAR on a pan-tilt kit

Since I learned about point clouds a while ago, I wanted to gain some practical experience with them. The goal was to scan a terrain / landscape-like scene, using an as basic as possible hardware setup, not a depth camera.

I used a LIDAR-Lite (a laser based distance sensor), mounted on a pan-tilt kit, driven by servos to position the sensor. All those devices were controlled by an Arduino, which streamed the sensor data back to a PC. To avoid problems with outdoor light, I added some wavy terrain-like features to a room, and scanned it instead of an outdoor scene.

Finally, I wrote my own software to compute each voxel (3D point / pixel in space) from the sensor data and servo angles, such that I could render them as a depth map and a point cloud, with various methods.

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Magnetic-core memory on an Arduino shield

Core memory is the simplest kind of main memory you could build from really basic components (no chips!), and easy enough to understand well.

I always wanted to understand computers to their core (no pun intended), and to build one myself from the ground up. The following kit seems to make it quite fun to do that for working memory (RAM), while being physically large scale enough to allow for inspecting and measuring what is going on.

In the picture above, the core memory itself is just the wire net on the left with the small rings (that look like beads/dots). Enjoyably simple.

The chips on the board are there to easily write and read the hand-built memory and to provide an interface to an Arduino (or other microcontroller).

The kit comes with all the necessary components, including the PCB, magnetic cores, wires, etc., while requiring some soldering to assemble it. Head over to Jussi’s blog to read the complete documentation for the shield and how to get one.

A fully functioning DIY bread-board computer

Ben Eater has created an excellent 8-bit computer that is true to the essential architecture of modern computers, yet is simple enough to fit on a few breadboards. It uses DIP-switches and push buttons as inputs, and LEDs and 7-segment displays as (debug) outputs. Even step-wise execution by stepping the computer clock is possible, such that every part of the computer can be observed as it functions and the internal state and memory can be modified by switches.

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How pull-up resistors really work

There are many explanations of pull-up or pull-down resistors that gloss a bit too much over the details, keeping you in doubt about how they really work, especially in conjunction with microcontrollers.

To improve our understanding, we will use a simplified schematic that models a microcontroller input-pin connected to a switch and a pull-up resistor. Then we calculate the voltages on the input-pin resulting from a closed or open switch.

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