microcontroller

387 Articles

Hackaday Prize 2023: AC Measurements Made Easy

October 12, 2023 by 17 Comments

When working on simple DC systems, a small low-cost multimeter from the hardware store will get the job done well enough. Often they have the capability for measuring AC, but this is where cheap meters can get tripped up. Unless the waveform is a perfect sinusoid at a specific frequency, their simple algorithms won’t be able to give accurate readings like a high-quality meter will. [hesam.moshiri] took this as a design challenge, though, and built an AC multimeter to take into account some of the edge cases that come up when working with AC circuits, especially when dealing with inductive loads.

The small meter, an upgrade from a previous Arduino version that is now based on the ESP32, is capable of assessing root mean square (RMS) voltage, RMS current, active power, power factor, and energy consumption after first being calibrated using the included push buttons. Readings are given via a small OLED screen and have an accuracy rate of 0.5% or better. The board also includes modern design considerations such as galvanic isolation between the measurement side of the meter and the user interface side, each with its own isolated power supply.  The schematics and bill-of-materials are also available for anyone looking to recreate or build on this design.

With the project built on an easily-accessible platform like the ESP32, it would be possible to use this as a base to measure other types of signals as well. Square and triangle waves, as well as signals with a large amount of harmonics or with varying frequencies, all need different measurement techniques in order to get accurate readings. Take a look at this classic multimeter to see what that entails.

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How Small Can The ESP32 Get?

September 7, 2023 by 25 Comments

At its core, the ESP32 chip is not much more than an integrated circuit, a huge mass of transistors sealed inside an epoxy resin package with some leads. Of course, most of us won’t buy discrete ESP32 chips with no support circuitry since it’s typically easier and often not that much more expensive to get them paired with development boards of some type for easy access to things like USB and GPIO. But these tiny chips need little in the way of support to get up and running as [Paul] demonstrates with this tiny ESP32 board.

The project started as a challenge for [Paul] to build the smallest ESP32 that would still function. That means carving away nearly everything normally found accompanying one of these chips. There is no charging circuitry, only one of the GPIO pins is accessible, and it even foregoes the WiFi antennas which eliminates the major reason most people would reach for this chip in the first place. But at this form factor even without wireless capabilities it still blows other chips of this stature, like the ATtiny series, out of the water.

Even though [Paul] built it as a challenge, it goes a long way to demonstrate what’s really needed to get one of these chips up and running properly. And plenty of projects don’t need a ton of I/O or Wi-Fi either, so presuming these individual chips can be found cheaply and boards produced for various projects its an excellent way to minimize size and perhaps even power requirements. You can make these boards even smaller than a USB-A connector if you want to take this process even further, too.

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Streaming Video From An ESP32

September 5, 2023 by 11 Comments

The ESP32, while first thought to be little more than a way of adding wireless capabilities to other microcontrollers, has quickly replaced many of them with its ability to be programmed as its own platform rather than simply an accessory. This also paved the way for accessories of its own, such as various sensors and even a camera. This guide goes over taking the input from the camera and streaming it out over the network to multiple browsers.

On the server side of things, the ESP32 and its attached camera are set up with MQTT, a lightweight communications protocol which uses a publish/subscribe model to send information. The ESP32 is configured to publish its images only, but not subscribe to any other nodes. On the client side, the browser runs a JavaScript program which is able to gather these images and stitch them together into a video.

This can be quite a bit of data to send out over the ESP32’s compact hardware, so there are some tips and tricks for getting more out of these little devices, including using an external antenna for better Wi-Fi signal, or omitting it entirely in favor of Ethernet. As far as getting a lot out of a tiny microcontroller, though, leveraging MQTT really helps the ESP32 go a long way. These chips have come along way since they were first introduced; they’re powerful enough to act as 8-bit gaming consoles too.

Thanks to [Surfskidude] for the tip!

Hands-Free Compass Uses Haptic Feedback

September 5, 2023 by 15 Comments

If you’ve never experienced it before, getting turned around on a cloudy day in the woods or getting lost during an event like a snowstorm can be extremely disorienting and stressful — not to mention dangerous. In situations where travel goes outside the beaten path, it’s a good idea to have some survival gear around, including a good compass. But if you need your hands for other things, or simply don’t want to have to stop often to check a compass, you might want to try out something like this belt-mounted haptic feedback compass.

The compass is based around a Raspberry Pi Pico microcontroller and uses a ULN2803a transistor array chip to control a series of motors. The motors are mounted all along a belt using custom 3D printed clips with wires woven to each through the holes in the belt. The firmware running on the belt communicates with an Android app via USB to control each of the motor’s vibration based on the direction the wearer is traveling and their desired heading. With certain patterns, the wearer can get their correct heading based on the vibrations they feel through the belt.

While it does rely on having a functioning phone, a modern smartphone’s built-in compass doesn’t require a signal to work. We would still recommend having a good simple compass in your pack as backup if you’re going to be far off the beaten path, though. There are other ways of navigation besides by compass, map, or GPS too. Have a shot at inertial navigation if you want a challenge.

Thanks to [Peter] for the tip!

Patching Together Logic Gates

August 25, 2023 by 14 Comments

The digital world offers many advantages over its analog relatives, the use of boolean logic among them. Some of the functions, like NOT, OR, and AND are fairly straightforward and line up nicely with their linguistic counterparts. Others are more elusive, like XOR and NAND. For those just getting their start in digital logic, this teaching tool allows different logic gates to be wired together with patch cables.

While [David] first thought to use 74-series logic circuits directly, a much more versatile solution was to use configurable custom logic — a feature found in AVR DA-series microcontrollers that allows for the creation of custom logic circuits without the need for external hardware or complex programming. He went with an ATmega4809 which is capable of supporting twelve gates which are depicted graphically on the board, where the patch cables can be connected between inputs and outputs from a set of switches on the left to another set of LEDs on the right. The microcontroller continually polls for connections, applies the correct logic via a lookup table, and lights the appropriate LED.

Even with only twelve gates, the amount of real-world analogs that can be created with this teaching tool are numerous and varied, from simple things like displaying traffic light patterns in the correct order to implementing a binary adder. It’s an excellent way to get started in digital logic or understanding gates, and much simpler than dealing with 74-series chips on a breadboard like many of us might have done, but those logic chips can be powerful tools to have on hand even in the modern world of microcontrollers.

RPDot: The RP2040 Dev Board Barely Bigger Than The Chip

August 25, 2023 by 33 Comments

Is [William Herr]’s RPDot actually the world’s smallest RP2040 dev board? We can’t say for sure, but at 10 mm on a side, we’d say it has a pretty good shot at the record.

Not that it really matters, mind you — the technical feat of building a fully functional dev board that’s only 3 mm longer on each side than the main chip is the kind of stuff we love to see. [William] says he took inspiration from the [SolderParty] RP2040 Stamp, which at one inch (25.4 mm) on a side is gigantic compared to the RPDot. Getting the RP2040 and all the support components, which include an 8MB QSPI Flash chip, a 3V3 LDO, a handful of 0201 passives, and even a pair of pushbuttons, required quite a lot of design tweaking. He started his PCB design as a four-layer board; while six layers would have made things easier, the budget wouldn’t allow such extravagance for a prototype. Still, he somehow managed to stuff everything in the allotted space and send the designs off — only to get back defective boards.

After reordering from a different vendor, the real fun began. Most of the components went on the front side of the board and were reflowed using a hot plate. The RP2040 itself needed to go on the back side, which required gentle hot air reflow so as not to disrupt the other side of the board. The results look pretty good, although those castellated edges look a little worse for the wear. Still, for someone who only ever worked with 0402 components before, it’s pretty impressive.

[William] says he’s going to open-source the designs as well as make some available for sale. We’ll be looking out for those and other developments, but for now, it’s just pretty cool to see such SMD heroics.

Linux, Running On Not A Lot

August 19, 2023 by 31 Comments

There are many possible answers to the question of what the lowest-powered hardware on which Linux could run might be, but it’s usually a pre-requisite for a Linux-capable platform to have a memory management unit, or MMU. That’s not the whole story though, because there are microcontroller-focused variants of the kernel which don’t require an MMU, including one for the Xtensa cores found on many Espressif chips. It’s this that [Naveen] is using to produce a computer which may not be the Linux computer with the lowest processor power, but could be the one consuming the least electrical power.

The result is definitely not a Linux powerhouse, but with its Arduino-sourced ESP32 board stacked on an UNO and I2C keyboard and display, it’s an extremely lightweight device. The question remains, though, is it more than a curiosity, and to what can it do? The chief advantage it has over its competitors such as the Raspberry Pi Zero comes in low power consumption, but can its cut-down Linux offer as much as a full-fat version? We are guessing that some commenters below will know the answer.

If you’re curious about the Xtensa version of Linux, it can be found here,