When it comes to things that hackers build, PCBs are a sizeable portion of our creative output. It’s no wonder – PCB design is a powerful way to participate in the hardware world, making your ideas all that more tangible with help of a friendly PCB fab. It’s often even more lovely when the PCB has been designed for you, and all you have to do is press “send” – bonus points if you can make a few changes for your own liking!
A lot of the time, our projects are untrodden ground, however, and a new design needs to be born. We pick out connectors, work through mechanical dimensions, figure out a schematic and check it with others, get the layout done, and look at it a few more times before sending it out for production. For a basic PCB, that is enough – but of course, it’s no fun to stop at ‘basic’, when there’s so many things you can do at hardly any cost.
Let’s step back a bit – you’ve just designed a board, and it’s great! It has all the chips and the connectors you could need, and theoretically, it’s even supposed to work first try. Now, let’s be fair, there’s an undeniable tendency – the more PCBs you design, the better each next one turns out, and you learn to spend less time on each board too. As someone with over two hundred PCBs under her belt, I’d like to show you a bunch of shortcuts that make your PCB more helpful, to yourself and others.
There’s a few ways that you can share your PCB projects in a more powerful way – I’d like to point out a few low-hanging fruits, whether README.md files or markings on the PCB itself. I’ve been experimenting quite a bit with external and embedded documentation of PCBs, as well as PCB sharing methods, got some fun results, and I’d like to share my toolkit through a few punchy examples and simple tricks. I’d also like to hear about yours – let’s chat! Continue reading “Share Your Projects: Making Helpful PCBs”→
Quick references are handy, but sometimes it’s nice to have a process demonstrated from beginning to end. In that spirit, [Darren Stone] created a video demonstrating how to model a twisted part in FreeCAD, showing the entire workflow of creating the part as a blend of surfaces and curves that get turned into a solid.
FreeCAD is organized using the concept of multiple “workbenches” which are each optimized for different tools and operations, and [Darren] walks through doing the same jobs in a few different ways.
This twisted bracket is a simple part that is nevertheless nontrivial from a CAD perspective, and that makes it a good candidate for showing off the different workbenches and tools.
The video below is also pretty good overall demonstration of what designing a part from a mechanical drawing looks like when done in FreeCAD. As for mechanical drawings themselves, we’ve seen FreeCAD can be used to make those, too.
If you ever work with a circuit that controls a decent amount of current, you will often encounter a FET – a Field-Effect Transistor. Whether you want to control a couple of powerful LEDs, switch a USB device on and off, or drive a motor, somewhere in the picture, there’s usually a FET doing the heavy lifting. You might not be familiar with how a FET works, how to use one and what are the caveats – let’s go through the basics.
Here’s a simple FET circuit that lets you switch power to, say, a USB port, kind of like a valve that interrupts the current flow. This circuit uses a P-FET – to turn the power on, open the FET by bringing the GATE signal down to ground level, and to switch it off, close the FET by bringing the GATE back up, where the resistor holds it by default. If you want to control it from a 3.3 V MCU that can’t handle the high-side voltage on its pins, you can add a NPN transistor section as shown – this inverts the logic, making it into a more intuitive “high=on, low=off”, and, you no longer risk a GPIO!
This circuit is called a high-side switch – it enables you to toggle power to a device at will through a FET. It’s the most popular usecase for a FET, and if you’re wondering more about high-side switches, I highly recommend this brilliant article by our own [Bil Herd], where he shows you high-side switch basics in a simple and clear way. For this article, you can use this schematic as a reference of how FETs are typically used in a circuit.
80s-era electronic speech certainly has a certain retro appeal to it, but it can sometimes be a useful data output method since it can be implemented on very little hardware. [luc] demonstrates this with a talking thermometer project that requires no display and no special hardware to communicate temperatures to a user.
Back in the day, there were chips like the Votrax SC-01A that could play phonemes (distinct sounds that make up a language) on demand. These would be mixed and matched to create identifiable words, in that distinctly synthesized Speak & Spell manner that is so charming-slash-uncanny.
Nowadays, even hobbyist microcontrollers have more than enough processing power and memory to do a similar job entirely in software, which is exactly what [luc]’s talking thermometer project does. All this is done with the Talkie library, originally written for the Arduino and updated for the ESP32 and other microcontrollers. With it, one only needs headphones or a simple audio amplifier and speaker to output canned voice data from a project.
[luc] uses it to demonstrate how to communicate to a user in a hands-free manner without needing a display, and we also saw this output method in an electric unicycle which had a talking speedometer (judged to better allow the user to keep their eyes on the road, as well as minimizing the parts count.)
Would you like to listen to an authentic, somewhat-understandable 80s-era text-to-speech synthesizer? You’re in luck, because we can show you an authentic vintage MicroVox unit in action. Give it a listen, and compare it to a demo of the Talkie library in the video below.
It starts with the actual board itself. Many SMD boards have at least some flux left over from the assembly process, which the duo notes has a tendency to pull water in under components. So the first step is to clean them thoroughly with an ultrasonic cleaner or toothbrush, though some parts such as RTCs, MEMs, or pressure sensors need to be handled with significant care.
Actual waterproofing starts with a coating like 422-B or nail polish which each have pros and cons. [Patricia] and [Edward] often apply coatings to PCBs even if they plan to otherwise seal it as it offers a final line of defense. The cut edges of PCBs need to be protected so that water can’t seep between layers, though care needs to be made for connectors like SD cards.
Encapsulation with a variety of materials such as hot glue, heat shrink tubing, superglue and baking soda, silicone rubber, liquid epoxy, paste epoxy (like J-B Weld), or even wax are all commented on. The biggest problem is that a material can be waterproof but not water vapor proof. This means that condensation can build up inside a housing. Temperature swings also can play havoc with sealings, causing gaps to appear as it expands or contracts.
In our previous article on Ball Grid Arrays (BGAs), we explored how to design circuit boards and how to route the signals coming out of a BGA package. But designing a board is one thing – soldering those chips onto the board is quite another. If you’ve got some experience with SMD soldering, you’ll find that any SOIC, TQFP or even QFN package can be soldered with a fine-tipped iron and a bit of practice. Not so for BGAs: we’ll need to bring out some specialized tools to solder them correctly. Today, we’ll explore how to get those chips on our board, and how to take them off again, without spending a fortune on equipment.
Last year, I found myself compelled to make a scaled-down replica of the iconic test chamber signs from the video game Portal. If you’ve played the game, you’ll remember these signs as the illuminated monoliths that postmarked the start of every test chamber. In hyperstylized video game fashion, they were also extremely thin.
True to the original, my replica would need to be both slimmed down and backlit with a uniform, natural white glow. As fate would have it, the crux of this project was finding a way to do just that: to diffuse light coming in from the edges so that it would emit evenly from the front.
What I thought would be quick project ended up being a dive down the rabbit hole that yielded some satisfying results. Today, I’d like to share my findings and introduce you to light guide plates, one of the key building blocks inside of much of today’s backlit screen technology. I’ll dig into the some of the working principles, introduce you to my homebrew approach, and leave you with some inspirational source code to go forth and build your own. Continue reading “A Hacker’s Introduction To DIY Light Guide Plates”→