DIY Vacuum Table Enhances PCB Milling

CNC milling a copper-clad board is an effective way to create a PCB by cutting away copper to form traces instead of etching it away chemically, and [loska] has improved that process further with his DIY PCB vacuum table. The small unit will accommodate a 100 x 80 mm board size, which was not chosen by accident. That’s the maximum board size that the free version of Eagle CAD will process.

When it comes to milling PCBs, double-sided tape or toe clamps are easy solutions to holding down a board, but [loska]’s unit has purpose behind its added features. The rigid aluminum base and vacuum help ensure the board is pulled completely flat and held secure without any need for external fasteners or adhesives. It’s even liquid-proof, should cutting fluid be used during the process. Also, the four raised pegs provide a way to reliably make double-sided PCBs. By using a blank with holes to match the pegs, the board’s position can be precisely controlled, ensuring that the back side of the board is cut to match the front. Holes if required are drilled in a separate process by using a thin wasteboard.

Milling copper-clad boards is becoming more accessible every year; if you’re intrigued by the idea our own [Adil Malik] provided an excellent walkthrough of the workflow and requirements for milling instead of etching.

How To Deal With A Cheap Spectrum Analyzer

The Hackaday Superconference is all about showcasing the hardware heroics of the Hackaday community. We also have a peer-reviewed journal with the same goal, and for the 2018 Hackaday Superconference we got a taste of the first paper to make it into our fully Open Access Journal. It comes from Ted Yapo, it is indeed a tale of hardware heroics: what happens when you don’t want to spend sixty thousand dollars on a vector network analyzer?

Ted’s talk begins with a need for a network analyzer. These allow for RF measurements, but if you ever need one, be prepared: you can spend twenty thousand dollars on a used VNA. Around the time Ted’s project began, Rigol released their cheap spectrum analyzer, the DSA815. This thing only cost a thousand dollars. It was their first revision of the hardware, and it was only a scalar network analyzer. Being the first revision of the hardware, there were a few problems; there was leakage that would affect the measurement. The noise floor was higher than it should have been. These problems can be corrected, though, with a little bit of cunning from Ted:

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Video: Putting High Speed PCB Design To The Test

Designing circuit boards for high speed applications requires special considerations. This you already know, but what exactly do you need to do differently from common board layout? Building on where I left off discussing impedance in 2 layer Printed Circuit Board (PCB) designs, I wanted to start talking about high speed design techniques as they relate to PCBs.  This is the world of multi-layer PCBs and where the impedance of both the Power Delivery Network (PDN) and the integrity of the signals themselves (Signal Integrity or SI) become very important factors.

I put together a few board designs to test out different situations that affect high speed signals. You’ve likely heard of vias and traces laid out at right angles having an impact. But have you considered how the glass fabric weave in the board itself impacts a design? In this video I grabbed some of my fanciest test equipment and put these design assumptions to the test. Have a look and then join me after the break for more details on what went into this!

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Break Your Scope’s Bandwidth Barrier

Oscilloscope bandwidth is a tricky thing. A 100 MHz scope will have a defined attenuation (70%) of a 100 MHz sine wave. That’s not really the whole picture, though, because we aren’t always measuring sine waves. A 100 MHz square wave, for example, will have sine wave components at 100 MHz, 300 MHz, and the other odd harmonics. However, it isn’t that a 100 MHz scope won’t show you something at a higher frequency — it just doesn’t get the y-axis right. [Daniel Bogdanoff] from Keysight decided to think outside of the box and made a video about using scopes beyond their bandwidth specification. You can see that video, below.

[Daniel] calls this a “spec hacks” but they aren’t really hacks to the scope. They are just methods that don’t care about the scope’s rated bandwidth. In this particular spec hack, he shows how the frequency counter using a 70 MHz scope’s trigger circuit can actually read up to 410 MHz. A 100 MHz scope was able to read almost 530 MHz.

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Adventures In Photopolymers With Ben Krasnow

There is a technology that will allow you to add inks, resins, and paints to any flat surface. Screen printing has been around since forever, and although most of the tutorials and guides out there will tell you how to screen print onto t-shirts, [Ben Krasnow] had the idea of putting patterns of paint on acrylic, metal, or even ITO glass for electroluminescent displays. With screen printing, the devil is in the details, but lucky enough for all of us, [Ben] figured everything out and is sharing his knowledge with us.

The ten thousand foot view of screen printing is simple enough — put some ink on a screen that has some photoemulsion, and squeegee it through onto a t-shirt. While this isn’t wrong, there’s a lot of technique, and things will go wrong if this is your first time doing it. Screens are easy, and the best way to get those is by buying a pre-stretched frame. The photoemulsion is a bit different. The old way of applying a photoemulsion is by squeegeeing it on with a bizarre tool. It’s almost impossible to get a thin consistent layer with this technique, so [Ben] recommends just buying some photoemulsion film.

Once the photoemulsion is on the screen and dry, you need to put an image on this. The photoemulsion cures hard with UV, so the traditional technique is using transparency (actually, the real old-school way is using a camera obscura…). Transparency sheets for laser printers work, but 30-lb vellum is actually more transparent to UV light than clear acetate sheets. This is then applied print side down to the dry screen, and believe me when I say this is the most important part. You will not get a good screen print if there is not direct contact between your photomask and your photoemulsion. This is so important, it may be worth considering some experiments in vinyl cutting to create the photomask.

With the screen developed, it’s simply a matter of globbing on some ink and pressing it onto a piece of acrylic. [Ben] used regular oil paints, an unmixed artists’ oil paint, and the professional solution, epoxy-based screenprinting paint. By far, the epoxy paint gave the best finish, but it’s a stinky mess that is nearly impossible to clean.

With a somewhat successful screenprinting setup, what will [Ben] be able to do? Well, he’s been working on electroluminescent displays, and the first EL displays were screenprinted anyway. More than that, you could use screen printing to create a resist for copper etching for creating your own PCBs. There’s a lot you can do when you can put epoxy down in a thin layer, like make a blockchain of Tide pods, and this is the best tutorial we’ve ever seen on using photoemulsions.

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Understanding Modulated RF With [W2AEW]

There was a time — not long ago — when radio and even wired communications depended solely upon Morse code with OOK (on off keying). Modulating RF signals led to practical commercial radio stations and even modern cell phones. Although there are many ways to modulate an RF carrier with voice AM or amplitude modulation is the oldest method. A recent video from [W2AEW] shows how this works and also how AM can be made more efficient by stripping the carrier and one sideband using SSB or single sideband modulation. You can see the video, below.

As is typical of a [W2AEW] video, there’s more than just theory. An Icom transmitter provides signals in the 40 meter band to demonstrate the real world case. There’s discussion about how to measure peak envelope power (PEP) and comparison to average power and other measurements, as well.

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Lathe’s Tool Holder Holds A Rotary Tool

What is better than a tool? Two. What is better than two? Two tools tooling together. [tintek33] wanted a rotary tool to become an attachment on his mini lathe, the video is also below the break. Fortunately, Dremels and Proxxons are built to receive accessories, or in this case, become one. Even if the exact measurements do not apply to your specific hardware, we get to see the meat of the procedure from concept to use.

We start with where the rotary tool should be and get an idea of what type of bracket will be necessary. The design phase examines the important dimensions with a sketch and then a CAD mock-up. Suitably thick material is selected, and the steps for pulling the tool from the raw stock are shown with enough detail to replicate everything yet there is no wasted time in this video. That is important if you are making a quick decision as to whether or not this is worth your hard work. Once the brace is fully functional and tested, it is anodized for the “summer ocean” blue color to make it easy to spot in the tool heap. Some complex cuts are made and shown close-up.

Thank you [jafinch78] for your comment on Take a Mini Lathe for a Spin and check out [tintek33] using his mini lathe to make a hydraulic cylinder for an RC snow plow.

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