A New KiCAD Tutorial Hits The Scene

July 29, 2019 by Kerry Scharfglass 42 Comments

KiCAD has a rightfully earned image problem regarding beginners. The shiny new version 5 has improved things (and we’re very excited for v6!) but the tool is a bit obtuse even when coming from a electronics design background, so we’re always excited to see new learning material. [Mike Watts] is the latest to join the esteemed group of people willing to export their knowledge with his KiCAD tutorial series on GitHub that takes the aspiring user from schematic through fab and assembly.

The tutorial is focused around the process of creating a development board for the dimuitive Microchip née Atmel ATSAMD10 Cortex M0 ARM CPU. It opens by asking the reader to create a schematic and proceeds to teach by directing them to perform certain actions then explaining what’s going on and which shortcuts can accelerate things. This method continues through layout, manufacturing, and assembly.

Of note is that when defining the board outline [Mike] describes how to use OpenSCAD to parametrically define it; a neat micro-tutorial on using the two great tools to compliment each other. We also love that upon successful completion of the tutorial series the user will have developed a tiny but useful development board that can be assembled for about $3 in single quantities!

As with all open source work, if you have quibbles or want to contribute open a pull request and give [Mike] a hand!

High Precision Analog IO With Digital Pins

July 22, 2019 by Kerry Scharfglass 27 Comments

Reading the temperature of your environment is pretty easy right? A quick search suggests the utterly ubiquitous DHT11, which speaks a well documented protocol and has libraries for every conceivable microcontroller and platform. Plug that into your Arduino and boom, temperature (and humidity!) readings. But the simple solution doesn’t hit every need, sometimes things need to get more esoteric.

The technique summarized by an image from Microchip Appnote AN685

For years we’ve been watching [Edward]’s heroic efforts to build accessible underwater sensing hardware. When we last heard from him he was working on improving the accuracy of his Arduino’s measurements of the humble NTC thermistor. Now the goal is the same but he has an even more surprising plan, throw the ADC out entirely and sample an analog thermistor using digital IO. It’s actually a pretty simple trick based on an intuitive observation, that microcontrollers are better at measuring time than voltage.

The circuit has a minimum of four components: a reference resistor, the thermistor, and a small capacitor with discharge resistor. To sense you configure a timer to count, and an edge interrupt to capture the value in the timer when its input toggles. One sensing cycle consists of discharging the cap through the discharge resistor, enabling the timer and interrupt, then charging it through the value to measure. The value captured from the timer will be correlated to how long it took the cap to charge above the logic-high threshold when the interrupt triggers. By comparing the time to charge through the reference against the time to charge through the thermistor you can calculate their relative resistance. And by performing a few calibration cycles at different temperatures ([Edward] suggests at least 10 degrees apart) you can anchor the measurement system to real temperature.

For all the gory details, including tips for how to save every last joule of energy, check out [Edward]’s post and the Microchip appnote AN685 he references. Besides this series [Edward]’s Cave Pearl Project has already yielded an impressive number of Hackday posts. For more great hardware writeups check out a general hardware build for a single sensing node, or the “temperature sensor” [Edward] made with no external parts at all!

A Microwave Kiln, From Scratch

July 20, 2019 by Jenny List 15 Comments

We are normally told that microwave ovens are strictly for food only, and that anything else will cause all sorts of bad things to come our way. There can be few readers who haven’t at some time seen the shower of sparks when an inadvertent metallic object finds its way onto the turntable.

A particularly useful non-food application for a microwave oven comes in the form of the small kilns sold for glass fusing. These are ceramic cylinders coated internally with silicon carbide, and [ShakeTheFuture] shows us how to make your own.

Key to the process is ceramic fibre insulation, which is bonded both to itself and to the fused silicon carbide grit by a cured solution of waterglass, sodium silicate. The result can easily reach the required temperature for fusing glass, but also has an application in burning out surplus wax or PLA from a plaster mould. It’s particularly interesting to see the technique with the waterglass in action, and you can see a run-down of the whole thing in the video below the break.

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New Part Day: Two Millimeter Addressable LEDs

July 10, 2019 by Brian Benchoff 57 Comments

The WS2812, or “Neopixels”, or whatever you want to call them, are the standard when it comes to adding blinky to anything. These chips are individually addressable RGB LEDs, which you’ve seen in many LED strips and a thousand other products. These LEDs are rather big compared to normal, dumb LEDs, measuring 5 mm on each side. Here are WS2812s packed into a 2 mm x 2 mm square package. It’s the smallest and brightest blinky that works the same as the WS2812s you know and love.

This is the latest product from Worldsemi. We’ve heard of these before, but damned if we could find a supplier or even a price. Now they’re on AliExpress, at a price of $8 USD per 100, shipping not included.

Electrically, these appear to have the same properties of the normal, 5050-size WS2812 LEDs. Apply power and ground to two pins, send data in on one pin, and connect the next LED in the strand to the remaining pin. Yes, it requires a bit of work to turn this into a display, but microcontrollers are very fast now and have plenty of RAM. Attach a BeagleBone and you’ll be able to drive as many as your glowing heart desires.

If you’re wondering what the coolest project imaginable for these LEDs is, here’s the math: the largest (common) PCB panel for your random board house is 16 by 22 inches. Assuming a 3 mm pixel pitch, that means the largest PCB display you can make with these LEDs is 135 by 186 pixels, call it 120 by 180 just to make things easy. That’s 21,600 LEDs, at a cost of about $2,000. I would not recommend reflowing these, and assuming soldering a LED every thirty seconds, it will take about a month to solder them all by hand. There’s your project, now get to it.

Robot Harvesting Machine Is Tip Of The Agri-Tech Iceberg

July 9, 2019 by Pat Whetman 24 Comments

Harvesting delicate fruit and vegetables with robots is hard, and increasingly us humans no longer want to do these jobs. The pressure to find engineering solutions is intense and more and more machines of different shapes and sizes have recently been emerging in an attempt to alleviate the problem. Additionally, each crop is often quite different from one another and so, for example, a strawberry picking machine can not be used for harvesting lettuce.

A team from Cambridge university, UK, recently published the details of their lettuce picking machine, written in a nice easy-to-read style and packed full of useful practical information. Well worth a read!

The machine uses YOLO3 detection and classification networks to get localisation coordinates of the crop and then check if it’s ready for harvest, or diseased. A standard UR10 robotic arm then positions the harvesting mechanism over the lettuce, getting force feedback through the arm joints to detect when it hits the ground. A pneumatically actuated cutting blade then attempts to cut the lettuce at exactly the right height below the lettuce head in order to satisfy the very exacting requirements of the supermarkets.

Rather strangely, the main control hardware is just a standard laptop which handles 2 consumer grade USB cameras with overall combined detection and classification speeds of about 0.212 seconds. The software is ROS (Robot Operating System) with custom nodes written in Python by members of the team.

Although the machine is slow and under-powered, we were very impressed with the fact that it seemed to work quite well. This particular project has been ongoing for several years now and the machine rebuilt 16 times! These types of machines are currently (2019) very much in their infancy and we can expect to see many more attempts at cracking these difficult engineering tasks in the next few years.

We’ve covered some solutions before, including: Weedinator, an autonomous farming ‘bot, MoAgriS, an indoor farming rig, a laser-firing fish-lice remover, an Aussie farming robot, and of course the latest and greatest from FarmBot.

Video after the break:

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Safely Measuring Single And Three-Phase Power

July 6, 2019 by Maya Posch 7 Comments

There are many reasons why one would want to measure voltage and current in a project, some applications requiring one to measure mains and even three-phase voltage to analyze the characteristics of a device under test, or in a production environment. This led [Michael Klopfer] at the University of California, Irvine along with a group of students to develop a fully isolated board to analyze both single and three-phase mains systems.

Each of these boards consists out of two sections: one is the high-voltage side, with the single phase board using the Analog Devices ADE7953 and the three-phase board the ADE9708. The other side is the low-voltage, isolated side to which the microcontroller or equivalent connects to using either SPI or I2C. Each board type comes in either SPI or I2C flavor.

Each board can be used to measure line voltage and current, and the Analog Devices IC calculates active, reactive, and apparent energy, as well as instantaneous RMS voltage and current. All of this data can then be read out using the provided software for the Arduino platform.

The goal of this project is to make it easy for anyone to reproduce their efforts, with board schematics (in Eagle format) and the aforementioned software libraries provided. Here it is somewhat unfortunate that the documentation can be somewhat incomplete, with basic information such as input and measurement ranges missing. Hopefully this will improve over the coming months as it does seem like a genuinely useful project for the community.

We’ve covered the work coming out of [Michael]’s lab before, including this great rundown on Lattice FPGAs. They’re doing machine vision, work on RISC-Vchips, and more. A stroll through the lab’s GitHub is worth your time.

How Do You Get PCI-E On The Atomic Pi? Very Carefully.

June 26, 2019 by Tom Nardi 18 Comments

At this point, you’ve almost certainly heard about the Atomic Pi. The diminutive board that once served as the guts of a failed robot now lives on as a powerful x86 SBC available at a fire sale price. How long you’ll be able to buy them and what happens when the initial stock runs out is another story entirely, but there’s no denying that folks are already out there doing interesting things with them.

One of them is [Jason Gin], who recently completed an epic quest to add a PCI Express (PCI-E) slot to his Atomic Pi. Things didn’t exactly go according to plan and the story arguably has more lows than highs, but in the end he emerged victorious. He doesn’t necessarily recommend you try the same modification on your own Atomic Pi, but he does think this sets the stage for the development of a more refined upgrade down the line.

[Jason] explains that the board’s Ethernet controller was already communicating with the Intel Atom x5-Z8350 SoC over PCI-E, so there was never a question about whether or not the modification was possible. In theory, all you needed to do was disable the Ethernet controller and tack on an external PCI-E socket so you could plug in whatever you want. The trick is pulling off the extremely fine-pitch soldering such a modification required, especially considering how picky the PCI Express standard is.

In practice, it took several attempts with different types of wire before [Jason] was able to get the Atomic Pi to actually recognize something plugged into it. Along the way, he managed to destroy the Ethernet controller somehow, but that wasn’t such a great loss as he planned on disabling it anyway. The final winning combination was 40 gauge magnet wire going between the PCB and a thin SATA cable that is mechanically secured to the board with a piece of metal to keep anything from flexing.

At this point, [Jason] has tested enough external devices connected to his hacked-on port to know the modification has promise. But the way he’s gone about it is obviously a bit temperamental, and far too difficult for most people to accomplish on their own anyway. He’s thinking the way forward might be with a custom PCB that could be aligned over the Ethernet controller and soldered into place, though admits such a project is currently above his comfort level. Any readers interested in a collaboration?

Like most of you, we had high hopes for the Atomic Pi when we first heard about it. But since it became clear the board is the product of another company’s liquidation, there’s been some understandable trepidation in the community. Nobody knows for sure what the future looks like for the Atomic Pi, but that’s clearly not stopping hackers from diving in.