Designing A PCB GPS Antenna From Scratch

October 18, 2023 by Donald Papp 14 Comments

These days, when it comes to GPS devices the antenna is typically part of the package. But what better opportunity for [Pepijn] to learn how to make a GPS antenna from scratch for a badge add-on?

A patch antenna is an antenna of a flat design, which [Pepijn] was going to put directly on a PCB. However, there was added complexity due to GPS being a circularly polarized signal, and that meant doing some research.

Sadly, nowhere did [Pepijn] encounter a straightforward reference design or examples, but in the end success came from going with a truncated corner patch antenna design and using simulation software to figure out exactly what dimensions were needed. (The openEMS free simulation software didn’t bring success, but the non-free Sonnet with a trial license did the trick.) The resulting PCB may not look particularly complex, but every detail matters in such designs.

KiCad handled the PCB CAD design but the prototype came from cutting the PCB on a CNC machine instead of having it fabricated and shipped; a much cheaper and faster option for those with access to the right tools. A bit more testing had the prototype looking good, but the real proof came when it successfully received GPS signals and spewed valid NMEA messages. The design files are on GitHub but as [Pepijn] says, the project was about the journey more than anything else.

PCB Repair Is A Sticky Proposition

October 14, 2023 by Al Williams 9 Comments

What do you do when a PCB is cracked or even broken in two? [MH987] has a plan: superglue the board back and then bridge the traces with solder, solder paste, or wire. The exact method, of course, depends on the extent of the damage.

We’ve had some success with similar techniques, and, honestly, for single-sided boards, we would be tempted to add a thin backer behind the crack. We’ve also used conductive paint to repair traces, but it’s good to have having as many tricks as possible because you never know what will work best for a particular repair. The post mentions that this is easier to do on a single-sided board, but it is certainly possible to do on a two-layer board.

The example repair is a Walkman which — if you are a youngster — was a portable music player that takes cassette tapes. These haven’t been made since 2010, so it is important to repair what you have.

If you can’t repair your Walkman, you could build an updated version. If your board is seriously damaged, you might get hope from this more extreme repair.

An In-Depth Comparison Of Hobby PCB Manufacturers

October 13, 2023 by Richard Baguley 45 Comments

[Icamtuf] has been working on a prototyping run of a project, which involves getting PCBs made by several low volume PCB manufacturing companies. After receiving the boards, he analyzed the results and produced an interesting analysis.

The project he is working on is Sir-Box-A-Lot, a Sokoban gaming console clone that we’ve covered before. It uses an AVR128DA28 microcontroller to emulate the original box-pushing game and drive the OLED display. He ordered PCBs from OSHPark, DigiKey Red, JLCPCB, PCBWay and Aisler.

OSHPark boards are gorgeous, but you pay for it.

There were pros and cons for each of the services: OSHPark produced the nicest-looking boards, but at the highest cost. DigiKey Red had a flawless solder mask, but a rather sloppy-looking silkscreen and shipped the boards covered in adhesive gunk. JLCPCB was fast, shipping the boards in less than 7 days, but the smaller details of the silkscreen were blurry and the solder mask was thinner than the others. The solder mask from PCBWay was very slightly misaligned but was thicker than most, and they were the only ones who queried a badly shaped hole to see what [Icamtuf] wanted to do: the others just made assumptions and made the boards without checking.

To be fair, this analysis is based on a single PCB design ordered once and it is possible that some companies were having a bad day. These were also delivered to the US, so your delivery times may vary. So, there are no clear winners and I wouldn’t make a choice based on this alone. But the analysis is well worth a read if you want to know what to look out for on your own PCBs.

Try It Out

October 7, 2023 by Elliot Williams 21 Comments

It’s like Star Wars versus Star Trek at a SciFi convention, or asking creamy or chunky at the National Peanut Butter Appreciation Festival. (OK, we made that one up.) When Jenny reviewed the 1.0 version of LibrePCB, it opened the floodgates. Only on Hackaday!

Of course it makes sense that in a community of hardware hackers, folks who are not unfamiliar with the fine art and engineering of designing their own PCBs, have their favorite tools. Let’s face it, all PCB design software is idiosyncratic, and takes some learning. But the more fluent you are with your tool of choice, the more effort you have invested in mastering it, leading to something like the sunk-cost phenomenon: because you’ve put so much into it, you can’t think of leaving it.

The beauty of open-source software tools is that there’s almost nothing, aside from your own psychology, stopping you from picking up another PCB program, kicking the proverbial tires with a simple design, and seeing how it works for you. That’s what Jenny did here, and what she’s encouraged me to do. Whether it’s beginner-friendly Fritzing (also recently in version 1.0), upstarts LibrePCB or Horizon EDA, heavyweight champion KiCAD, or the loose-knit conglomeration of tools in coralEDA, you have enough choices that something is going to fit your PCB hand like a glove.

I certainly wouldn’t risk a swap up to a new tool on something super complicated, or something with a tight deadline, but why not start up a fun project to test it out? Maybe follow Tom Nardi’s lead and make a Simple Add-on, for a badge or just as a blinky to put on your desk? Don’t be afraid to try something new!

Chip Shortage Engineering: Misusing DIP Packages

October 3, 2023 by Tom Nardi 57 Comments

After years of seeing people showing off and trading their badge Simple Add-Ons (SAOs) at Supercon, this year I finally decided to make one myself. Now for a first attempt, it would have been enough to come up with some cool PCB art and stick a few LEDs on it. But naturally I started with a concept that was far more ambitious than necessary, and before long, had convinced myself that the only way to do the thing justice was to have an onboard microcontroller.

My first thought was to go with the venerable ATtiny85, and since I already had a considerable stock of the classic eight-pin DIP MCUs on hand, that’s what I started prototyping with. After I had something working on the breadboard, the plan was to switch over to the SOIC-8 version of the chip which would be far more appropriate for something as small as an SAO.

Unfortunately, that’s where things got tricky. I quickly found that none of the major players actually had the SMD version of the chip in stock. Both DigiKey and Mouser said they didn’t expect to get more in until early 2024, and while Arrow briefly showed around 3,000 on hand, they were all gone by the time I checked back. But that was only half the problem — even if they had them, $1.50 a piece seems a hell of a lot of money for an 8-bit MCU with 8K of flash in 2023.

The whole thing was made all the more frustrating by the pile of DIP8 ATtiny85s sitting on the bench, mocking me. Under normal circumstances, using them in an SAO wouldn’t really be a problem, but eight hand-soldered leads popping through the front artwork would screw up the look I had in mind.

While brooding over the situation my eyes happened to fall on one of the chips I had been fiddling with, it’s legs badly bent from repeated trips through the programmer. Suddenly it occurred to me that maybe there was a way to use the parts I already had…

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Bespoke Implants Are Real—if You Put In The Time

September 6, 2023 by Brian McEvoy 23 Comments

A subset of hackers have RFID implants, but there is a limited catalog. When [Miana] looked for a device that would open a secure door at her work, she did not find the implant she needed, even though the lock was susceptible to cloned-chip attacks. Since no one made the implant, she set herself to the task. [Miana] is no stranger to implants, with 26 at the time of her talk at DEFCON31, including a couple of custom glowing ones, but this was her first venture into electronic implants. Or electronics at all. The full video after the break describes the important terms.

The PCB antenna in an RFID circuit must be accurately tuned, which is this project’s crux. Simulators exist to design and test virtual antennas, but they are priced for corporations, not individuals. Even with simulators, you have to know the specifics of your chip, and [Miana] could not buy the bare chips or find a datasheet. She bought a pack of iCLASS cards from the manufacturer and dissolved the PVC with acetone to measure the chip’s capacitance. Later, she found the datasheet and confirmed her readings. There are calculators in lieu of a simulator, so there was enough information to design a PCB and place an order.

The first batch of units can only trigger the base station from one position. To make the second version, [Miana] bought a Vector Network Analyzer to see which frequency the chip and antenna resonated. The solution to making adjustments after printing is to add a capacitor to the circuit, and its size will tune the system. The updated design works so a populated board is coated and implanted, and you can see an animated loop of [Miana] opening the lock with her bare hand.

Biohacking can be anything from improving how we read our heart rate to implanting a Raspberry Pi.

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Where Did Your PCB Go Wrong? KiRI Knows

August 21, 2023 by Matthew Carlson 5 Comments

When working on a PCB design in KiCad, it’s helpful that the files are all text and can easily be checked into Git or other source control. However, stepping back through the revisions to determine where precisely a trace got routed wrong can be tricky. [Leandro] started with a simple script that exported the KiCad project to an image for inspection — over time it grew into a full-blown visual diff tool named KiCad Revision Inspector (KiRI).

The primary mechanism exports the revisions of a KiCad 5, 6, or 7 project to SVG, which can then be compared via a handy onion skin view. As this is a tool written for those using KiCad, shortcuts are a huge part of the experience. A command line interface generates artifacts to view the diff in any web browser. As these outputs have the KiRI tooling baked in, it is relatively easy to archive the output as a build artifact and allow easy access to review design changes.

For the long-time reader, you might remember back in 2018 talked about another diffing tool called plotgitsch (which this KiRI uses for KiCad 5 projects). KiCad has grown significantly in the last five years. It might be time to update our tips to utilize Git better for your PCB designs.

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