Working With BGAs: Design And Layout

The Ball Grid Array, or BGA package is no longer the exclusive preserve of large, complex chips on computer motherboards: today even simple microcontrollers are available with those little solder balls. Still, many hobbyists prefer to stay with QFP and QFN packages because they’re easier to solder. While that is a fair point, BGA packages can offer significant space savings, and are sometimes the only choice: with the ongoing chip shortage, some other package versions might simply be unavailable. Even soldering doesn’t have to be complicated: if you’re already comfortable with solder paste and reflow profiles, adding a BGA or two into the mix is pretty easy.

In this article we’ll show that working with BGA chips is not as difficult as it may seem. The focus will be on printed circuit board design: how to draw proper footprints, how to route lots of signals and what capabilities your PCB manufacturer should have. We’ll cover soldering and rework techniques in a future article, but first let’s take a look at why BGAs are used at all.

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Electronic Dice Is Introduction To Microcontroller Programming

By now most of us are familiar with the Arduino platform. It’s an inexpensive and fairly easy way into the world of microcontrollers. For plenty of projects, there’s no need to go beyond that unless you have a desire to learn more of the inner workings of microcontrollers in general. [Cristiano] was interested in expanding some of his knowledge, so he decided to build this electronic dice using a PIC microcontroller instead of the Arduino platform he was more familiar with.

As a result, this project is set up as a how-to for others looking to dive further into the world of microcontrollers that don’t have the same hand-holding setup as the Arduino. To take care of the need for a random number for the dice, the PIC’s random number generator is used but with the added randomness of a seed from an internal timer. The timer is started when a mercury tilt switch signals the device that it has been rolled over, and after some computation a single digit number is displayed on a seven-segment display.

While it might seem simple on the surface, the project comes with an in-depth guide on programming the PIC family of microcontrollers, and has a polish not normally seen on beginner projects, including the use of the mercury tilt switch which gives it a retro vibe. For some other tips on how to build projects like this, take a look at this guide on how to build power supplies for your projects as well.

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How To Get Your Diffraction Grating 3D Prints Right The First Time

Diffraction gratings are beautiful things, bending transmitted and reflected light and splitting it into its component wavelengths to create attractive iridescent rainbow patterns. It’s the same effect you see on the bottom of a CD!

You can 3D print a functional diffraction grating, too, with the right techniques, as it turns out! The average 3D printer can’t recreate the tiny-scaled patterns of a diffraction grating directly; a typical diffraction grating may have up to 1000 lines per mm. Instead, by 3D printing onto an existing diffraction grating, the print can pick up the texture on its base layer. It’s a great way to add iridescence and shine to a print.

We’ve seen similar work before, but the guide from [All3DP] goes into greater detail on how to get the effect to work just right. Getting the bed as close to perfectly level is key here, as is the first layer height. This is because the first layer of plastic has to meld perfectly with the diffraction grating to pick up the pattern. Too high and the grooves won’t transfer to the plastic, and too low, and it’s likely you’ll just melt the grating itself. Setting the Z-offset appropriately can help here.

Choosing the right bed temperature is also important to ensure the molten plastic is able to flow into the grooves of the grating. Again, the temperature at which the diffraction grating itself can survive is important to take into account; going above 90 degrees can be risky here. The guide also shows two methods of achieving the goal: one can either use an off-the-shelf grating, or one can prepare a no-longer-wanted CD into a suitable print surface.

Naturally, removing the print must be done delicately, lest one disturb the delicate structures key to generating the iridescent effect. [All3DP] recommends using a freezer to help separate the parts from the grating surface. It also bears noting that the print won’t survive excessive handling, as the grating structures will get damaged by physical touch.

It’s a great in-depth guide on how to get diffraction grating prints right. Meanwhile, consider diving deeper into the world of 3D printed optics!


Give 3D Printed Plastic A Well-Worn Metal Look

Affordable 3D printers let us turn ideas into physical reality without a big expensive workshop, but with their power came some disadvantages. The nature of FDM printers impart layer lines and nozzle ridges in the parts they produce. They can be minimized with optimized print settings, but never eliminated. [Emily Velasco] loves the power of 3D printing but not how the parts look. So she put in the effort to make 3D-printed plastic look like distressed metal and showed us how she did it. (Video also embedded after the break.)

This video is a follow-up to her Pet Eye project in response to feedback on Twitter. She had mentioned that the  salvaged metal box for Pet Eye wasn’t quite big enough to hold everything, so she had to extend its internal volume with a 3D print box on the back. It fit in so well that the offhand comment surprised many people who wanted to know more about how it was done. So she designed a demonstration cube covered with mechanical characteristics, and gave us this walkthrough of its transformation.

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Build-It-Yourself LC Meter

A basic digital multimeter (DMM) is usually the first measurement tool the aspiring electronics tinkerer buys. Even a bargain-bin DMM will happily measure voltage, current, and resistance; check continuity; and may even have a mode to measure transistor gain. Every toolbox needs at least one DMM, but most have an crucial limitation— they can’t measure two of the fundamental electrical quantities: inductance and capacitance. On, [core weaver] has developed an open-source LC meter to allow you to build your own tool to measure inductance and capacitance.

[core weaver]’s design is all through-hole, so even just assembling one would be a great exercise for someone getting started in electronics. However, he didn’t just release a design, in a series of videos he goes through the theory of the device’s operation; explains the design of the circuit, firmware, and case; and shows you how to put it all together. For times when you need to measure a lot of parts (e.g. if you have to sort a bag of cheap capacitors looking for specific value), he’s even developed a desktop program to save you some trouble!

The finished meter looks incredible! If you want to build one for yourself, he’s put all of the files up on GitHub, and we highly recommend you check out his first video after the break. If you’d like to build yourself a 6.5-digit DMM to go with our LC Meter, consider this one which even has a home-built ADC.

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Remoticon Video: How To Use Machine Learning With Microcontrollers

Going from a microcontroller blinking an LED, to one that blinks the LED using voice commands based on a data set that you trained on a neural net work is a “now draw the rest of the owl” problem. Lucky for us, Shawn Hymel walks us through the entire process during his Tiny ML workshop from the 2020 Hackaday Remoticon. The video has just now been published and can be viewed below.

This is truly an end-to-end Hello World for getting machine learning up and running on a microcontroller. Shawn covers the process of collecting and preparing the audio samples, training the data set, and getting it all onto the microcontroller. At the end of two hours, he’s able to show the STM32 recognizing and responding to two different spoken words. Along the way he pauses to discuss the context of what’s happening in every step, which will help you go back and expand in those areas later to suit your own project needs.

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Network Booting The Pi 4

We’ve talked about PXE booting the Raspberry Pi 3B+, and then looked at the Raspberry Pi 4 as a desktop replacement. But there’s more! The Pi 4 sports a very useful new feature, the flashable bootloader. Just recently a beta version of that bootloader was released that supports PXE  — booting up over the network — which has become a must-have for those of us who have had consistently bad experiences with root filesystems on SD cards.

Pi with no SD CardWhat are the downsides, I hear you ask? You might see slower speeds going across the network compared to a high quality SD card, particularly with the Pi 4 and its improved SD card slot. PXE does require an Ethernet cable; WiFi is not enough, so you have that restriction to contend with. And finally, this isn’t a portable option — you are tethered to that network cable while running, and tethered to your network to boot at all.

On the other hand, if you’re doing a permanent or semi-permanent install of a Pi, PXE is absolutely a winner. There are few things worse than dragging a ladder out to access a Pi that’s cooked its SD card, not to mention the possibility that you firewalled yourself out of it. Need to start over with a fresh Raspbian image? Easy, just rebuild it on the PXE server and reboot the Pi remotely.

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