Share Your Projects: Making Helpful PCBs

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 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”

FET: Fun Endeavors Together

Last time, we’ve looked over FET basics, details, nuances and caveats. Basics aren’t all there is to FETs, however – let’s go through real-world uses, in all their wonderful variety! I want to show you a bunch of cool circuits where a friendly FET, specifically a MOSFET, can help you – and, along the way, I’d also like to introduce you to a few FETs that I feel like you all could have a good long-term friendship with. If you don’t already know them, that is!

Driving Relays

Perhaps, that’s the single most popular use for an NPN transistor – driving coils, like relays or solenoids. We are quite used to driving relays with BJTs, typically an NPN – but it doesn’t have to be a BJT, FETs often will do the job just as fine! Here’s an N-FET, used in the exact same configuration as a typical BJT is, except instead of a base current limiting resistor, we have a gate-source resistor – you can’t quite solder the BJT out and solder the FET in after you have designed the board, but it’s a pretty seamless replacement otherwise. The freewheel (back EMF protection) diode is still needed for when you switch the relay and the coil produces wacky voltages in protest, but hey, can’t have every single aspect be superior.

The reason you can drive it the same way is quite simple: in the usual NPN circuit, the relay is driven by a 3.3 V or a 5 V logic level GPIO, and for small signal FETs, that is well within Vgs. However, if your MCU has 1.8 V GPIOs and your FET’s Vgs doesn’t quite cut it, an NPN transistor is a more advantageous solution, since that one will work as long as you can source the whatever little current and the measly 0.7 V needed.

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FET: The Friendly Efficient Transistor

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.

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Share Your Projects: Take Pictures

Information is diesel for a hacker’s engine, and it’s fascinating how much can happen when you share what you’re working on. It could be a pretty simple journey – say, you record a video showing you fixing your broken headphones, highlighting a particular trick that works well for you. Someone will see it as an entire collection of information – “if my headphones are broken, the process of fixing them looks like this, and these are the tools I might need”. For a newcomer, you might be leading them to an eye-opening discovery – “if my headphones are broken, it is possible to fix them”.

There’s a few hundred different ways that different hackers use for project information sharing – and my bet is that talking through them will help everyone involved share better and easier. Let’s start talking about pictures – perhaps, the most powerful tool in a hacker’s arsenal. I’ll tell you about all the picture-taking hacks and guidelines I’ve found, go into subjects like picture habits and simple tricks, and even tell you what makes Hackaday writers swoon!

To start with, here’s a picture of someone hotwiring a car. This one picture conveys an entire story, and a strong one.

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One of the PCB projects involved being held in the author's hands - a large-ish green board, with two Pi Picos visible on it

RP2040 And 5V Logic – Best Friends? This FX9000P Confirms!

Over the years, we’ve seen some modern microcontrollers turn out to be 5V-tolerant – now, RP2040 joins the crowd. Half a year ago, when we covered an ISA card based on a Pi Pico, [Eben Upton] left a comment saying that RP2040 is, technically, 5V tolerant for GPIO input purposes. The datasheets don’t state this because the reality of 5V tolerance isn’t the same as for natively 5V-tolerant chips – for instance, it doesn’t extend all the way to 5.5V for it to be ‘legally’ 5V-tolerant, as in, what 5V tolerance typically means when mentioned in a datasheet.

Having read that comment, [Andrew Menadue] has set out to test-drive the RP2040 GPIO capabilities, in a perfectly suited real-world scenario. He’s working with retro tech like Z80-era computers, using RP2040 boards for substituting entire RAM and ROM chips that have died in his FX9000P. Not only do the RP2040-driven replacements work wonders, using RP2040 boards also turns out to be way cheaper than sourcing replacements for chips long out of production!

Previously, [Andrew] used level shifter chips for interfacing the RP2040 with 5V systems, but he’s rebuilt a few designs of his without level shifters for the sake of this experiment. Now, he reports that, so far, those boards have been running long-term without problems. Together with [Eben]’s comment, this instills confidence in us when it comes to our RP2040 forays and 5V inputs.

There are a number of important caveats to this, that you should read up on. Some major points – certain GPIOs (like ADC ones) can’t take it, the GPIOs aren’t 5V-tolerant when set to output, and you shouldn’t feed the GPIOs 5V when the RP2040’s VDDIO is not powered up. [Andrew] points out one such case himself – one board of his has shed all level shifters except for the 8-bit address bus, which is driven by either the CPU or the RP2040 at different times, and that would result in 5V on an output-set GPIO when contention happens. All in all, if you’re working with 5V logic and your application is more hacking than business-critical stuff, you can shed the level shifters, too.

Continue reading “RP2040 And 5V Logic – Best Friends? This FX9000P Confirms!”

A Xiaomi 3 Lite dashboard with the panel taken off and the PCB visible, four wires connected to the SWD header.

Xiaomi Scooter Firmware Hacking Gets Hands-On

Scooter hacking is wonderful – you get to create a better scooter from a pre-made scooter platform, and sometimes you can do that purely through firmware modifications. Typically, hackers have been uploading firmware using Bluetooth OTA methods, and at some point, we’ve seen the always-popular Xiaomi scooters starting to get locked down. Today, we see [Daljeet Nandha] from [RoboCoffee] continue the research of the new Xiaomi scooter realities, where he finds that SWD flashing is way more of a viable avenue that we might’ve expected. Continue reading “Xiaomi Scooter Firmware Hacking Gets Hands-On”

Picture of the PCB with the text inside the copper pads

Silkscreen Busy? Put Labels Inside Pads

When making a PCB informative and self-documenting, there’s often just not enough space to silkscreen all the labels you want, and slowly but surely, you collect a set of tricks: using different through-hole pad shapes to denote ground or power pins, standardized pinouts for connectors, your own signal name shortening notations, and so on.

What if you have some large-ish signal pads on your board, and having the signal names on silkscreen just isn’t good enough? In this case, here’s a new trick for your toolkit: [Christoph] from [MakerProbe] shows us how he puts text directly inside the copper pads.

What you need is a set of Gerber files and a Python script. Technically, this ought to work with any PCB EDA, with [Christoph] using KiCad. You need to put the to-be-subtracted signal names on their very own layer, export Gerber files without features like aperture macros, then run the script. You’ll get a new copper layer as a result, it’s that simple. We also get a set of tips on what kinds of pads suit best and how to prepare them — and fancy-looking real-life examples. You get higher resolution than for on-silkscreen text, solderability isn’t impacted, and the labels are even visible after desoldering wires from the pads. What’s not to like?

Over on Twitter, [Makerprobe] have been doing things like 0201 tombstoning and BGA yield research – we say they’re worth a follow if you’d like to see someone pushing PCB boundaries! Innovative PCB design methods and tricks have a special spot in our hearts, what’s with things like this Tux-emblazoned desktop motherboard that’s also a guide on PCB aesthetics, and there’s a whole lot more you can do to make your PCBs pretty while preserving and even improving functionality. From turning rigid PCBs flexible to hiding components inside a PCB stack, there’s plenty of opportunities that we are yet to extract out of PCB world, and it’s lovely to see one more technique we can make use of.

Continue reading “Silkscreen Busy? Put Labels Inside Pads”