Old Firewall Reborn As Retro PC

January 17, 2022 by Chris Lott 16 Comments

We like projects where old gear is given a new life. [Splashdust] has a twenty-year old business firewall that’s build like a tank. He cracks it open and finds a complete x86 embedded motherboard inside, and sets off to restore it and turn it into a retro gaming computer (see the video from his Odd & Obsolete YouTube channel below the break).

This business firewall and router box is from a small Swedish firm Clavister, part of their S-Series from the early 2000s. The motherboard appears to be a generic one used in other equipment, and is powered by a VIA Eden ESP 4000 running at 400 MHz. The Eden line of x86 processors were low-power chips targeting embedded applications. The graphics chip is a Twister T by S3 Graphics which was purchased by VIA in 2000. After replacing the electrolytic capacitors, and making a few cables, [Splashdust] pops in a PCI sound card and boots up into Windows 98 from a CF card (we like the compact PCB vise he uses).

In two follow-up videos (here and here), he builds an enclosure (instructions on Thingiverse) and tries out several other operating systems. He was able to get the Tiny Core Linux distribution running with the NetSurf browser, but failed to get Windows 2000 or XP to work. Returning to Windows 98, he tweaks drivers and settings and eventually has a respectable retro-gaming computer for his efforts. The next time you’re cleaning out your junk bins, have a peek inside those pizza-box gadgets first — you may find a similar gem.

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Stout Peristaltic Pump Fabricated From Scratch

January 12, 2022 by Lewin Day 18 Comments

The peristaltic pump is perhaps most well known for its ability to pump fluids without the pump mechanism coming into contact with the working fluid. This is key for food-safe applications and other situations where a pump could contaminate the fluid. [Maciej Nowak] has built a great example of such a pump, crafted out of aluminium from scratch.

The build video covers the machining process in detail, showing how the aluminium body was fabricated on the lathe before installing bearings and a silicone hose. The pump shaft was then fabricated, along with a set of brass rollers to press along the tube, creating the pumping action. The rollers were also lubricated in order to reduce friction on the tubing. Powering the pump is a small DC motor, sending drive via a small toothed belt, giving the finished build quite an industrial look.

We’re used to seeing plenty of 3D-printed pumps about the place. This build, while it requires a fully-equipped machine shop, is much tougher than anything plastic, and you could easily use it to break a window in an emergency too, an obscure feature nevertheless requested by some discerning pump customers.

[Maciej] shows off the build by pumping some green liquid, noting the peristaltic design requires no priming which makes operation much easier. It’s also bidirectional, and can be run very slowly if required.

Overall, it’s a build that shows off the benefits of working in metal as well as the great features of the peristaltic pump design. Video after the break.

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A Simple EMF Detector And Electroscope You Can Make From Junk Box Parts

January 10, 2022 by Dave Rowntree 48 Comments

2N2222 devices used, but practically any junkbox NPN will do

Electromagnetic fields are everywhere, all around us. Some are generated naturally, but in vast majority of cases, it’s we humans that are generating them with artificial, electronic means. Everything from your mobile phone to the toaster will emit some sort of signal, be it intentional or not. So we think it only befits the general electronics-orientated hacker to have some way of sniffing around for these signals, so here is [Mirko Pavleski] with his take on a very simple pair of instruments to detect both static and dynamic electromagnetic fields.

CMOS clock input connected directly to the antenna. Warning! ESD damage risk!

The first unit (a simple electroscope) uses a cascade of 2N2222 NPN bipolar transistors configured to give a high current gain, so any charge near the antenna will result in increasing currents in subsequent stages, finally illuminating the LED. Simple stuff.

The second unit relies on the extremely high input impedance of the old-school CMOS 4017 decade counter, which is likely of the order of 100 MΩ or even more. Normally you would not leave such a CMOS input floating, or even connect it with too long a PCB trace — lest it pick up a stray signal —but for detecting alternating EM fields, this appears to work just fine. Configured as a simple divide-by-ten, when presenting 50 Hz AC, the LED can be seen to flash at 5 Hz.

Simple stuff, and this scribe has all those exact parts in the junk box, so will be constructing these shortly!

We’ve covered electroscopes for years, here’s a modern twist on a famous classic experiment, and some hair-raising experiments to get you started.

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Advanced PCB Graphics With KiCAD 6 And Inkscape

January 8, 2022 by Dave Rowntree 16 Comments

There are many, many video tutorials about designing the functional side of PCBs, giving you tips on schematic construction, and layout tips. What is a little harder to find are tutorials on the graphical aspects, covering the process from creating artworks and how you can drive the tools to get them looking good on a PCB, leveraging the silkscreen, solder and copper layers to maximum effect. [Stuart Patterson] presents his guide for Advanced PCB Graphics in KiCAD 6.0 and Inkscape, (Video, embedded below) to help you on your way to that cool looking PCB build.

Silkscreen layers in yellow, solder mask opening in red

The first step is to get your bitmap, whether you create it yourself, or download it, and trace it into a set of vectors using the Inkscape ‘trace bitmap’ tool. If you started with an SVG or similar vector shape, then you can skip that stage.

Next simply create a PCB outline shape by deleting all the details that aren’t part of the outline. A little scaling here and there to get the dimensions correct and you’re done with the first part. [Stuart] has an earlier video showing that process.

The usability improvements in KiCAD 6.0 are many, but one greatly demanded feature is the ability to group objects, just like you do in Inkscape and any other vector graphics tool for that matter. That means you can simply import that SVG outline into the Edge.Cuts PCB layer and all the curves will be nicely tied together. Next you select the details you want for the silkscreen layer, solder mask removal layers and any non-circuit copper. In Inkscape it would be wise to use the layers feature to assign the different material types to a uniquely named layer, so they can be hidden for exporting. This allows you to handle silk, mask and copper PNG exports from a single master file, in addition to any vector details for outline, slots and holes.

Once you have PNG bitmap exports for the silk, mask etc. you need to create a footprint inside a board-specific library, using the KiCAD image converter tool. It was interesting to note that you can export a new image footprint from the tool and paste it straight into the footprint editor, and tweak all the visibility details at the same time. That will save some time and effort for sure. Anyway, we hope this little tutorial from [Stuart] helps, and we will be sure to bring you plenty more in the coming months.

Need some more help with KiCAD? Checkout this tutorial, and if you want a bit more power from the tool, you need some action plugins!

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Production PCB And Pogo Pins Produce A Clever Test Jig

January 7, 2022 by Dave Rowntree 13 Comments

[Hans Summers] runs a site qrp-labs.com, selling self-assembly kits mostly for radio gear and GPS applications, and had some production problems with his QCX-mini QRP transceiver kit. They were using an assembly house that had some problems with a sub-contractor going under during the pandemic, and the replacement service was somewhat below the expected level of quality, resulting in a significant number of SMT populated boards coming out non-functional. Obviously, not wanting to pass these on to customers as a debug problem, they set to work on an in-house QA test jig, to give them the confidence to ship kits again. The resulting functional test jig, (video, embedded below) takes a fairly interesting approach. Skip the video to 9:00 for the description of the test jig and detailed test descriptions.

By taking an existing known-good PCB, stripping off all the SMT parts, and moving the through hole components to the rear PCB side, pogo pins could be soldered to strategic locations. Building the assembly into a rudimentary enclosure made from sawn-up raw copper clad board, with the pogos facing upwards, and a simple clamp on top, allowed the PCB-under-test (let’s call it the UUT from hereon) to be located and clamped in place. This compressed the pogos in order to make a firm electrical contact. A piece of MDF that had been attacked with a dremel did duty as a pressure plate, with cutouts around the SMT component areas to achieve the required uniform board pressure and keeping the force away from the delicate soldered parts. All this means that with an UUT connected via pogo pins to a through-hole only test PCB, the full circuit would be completed, if and only if the UUT was completely functional, and that means defect-free soldering and defect-free components.

Next the firmware was rewritten to do duty as the test controller, which when powered up would step through a sequence of test scenarios and measurements, logging the results to an OLED display and a serial interface. This rig survived 1,000 SMT tests without failing, giving [Hans] the confidence to ship out new kits and providing a database of datalog results as a backup should a customer have an issue during final assembly. All-in-all a smart idea to solve a difficult problem, with nary a custom test jig PCB in sight!

These pages have been graced with many a pogo-based test rig over the years. Here’s one to start, and if you’ve got a handy laser cutter and some scrap wood, making an accurate test rig is no bother either.

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555 Timer Contest Entry: A Digital Counter With Nothing But 555s

January 6, 2022 by Dan Maloney 11 Comments

With a 555 on the BOM, you never know what you’re going to get. With 40 of the versatile timer chips in a build, you might just get something completely unexpected, like this 555-based eight-bit digital counter.

This one comes to us by way of [Astronomermike], who chose to make a digital circuit with nothing but 555s and a largish handful of passives as his entry in the current 555 Timer Contest. The ubiquitous timer chip is not exactly the first chip that comes to mind for digital applications, but it does contain an SR latch, which only requires a little persuasion to become a JK flip flop. His initial design for the flip flop that would form the core of the circuit had a pair of 555s surrounded with a bunch of OR gates and inverters — within the rules of the contest but hardly in its spirit. Luckily, the 555 makes a fine inverter too, and along with some diode-resistor OR gates, the basic counter module was born.

The video below shows the design and build, as well as the trip down the troubleshooting rabbit hole courtesy of a bad breadboard. Each half-nibble stage of the 8-bit counter occupies a full breadboard with ten 555s; the whole 40-chip string actually works and looks pretty cool doing it.

Truth be told, this is exactly the kind of thing we had in mind when dreaming up this year’s 555 contest, so good on [Astronomermike] for thinking outside the box for this one. To see what other uses people have found for the chip that keeps on giving, or to get your entry in before the deadline on January 10, head over to the contest page.

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USB Power Has Never Been Easier

January 5, 2022 by Brian McEvoy 48 Comments

USB cables inevitably fail and sometimes one end is reincarnated to power our solderless breadboards. Of course, if the cable broke once, it is waiting to crap out again. Too many have flimsy conductors that cannot withstand any torque and buckle when you push them into a socket. [PROSCH] has a superior answer that only takes a couple of minutes to print and up-cycles a pair of wires with DuPont connectors. The metal tips become the leads and the plastic sheathing aligns with the rim.

The model prints with a clear plus sign on the positive terminal, so you don’t have to worry about sending the wrong polarity, and it shouldn’t be difficult to add your own features, like a hoop for pulling it out, or an indicator LED and resistor. We’d like to see one with a tiny fuse holder.

If you want your breadboard to have old-school features, like a base and embedded power supply, we can point you in the right direction. If you are looking to up your prototyping game to make presentation-worthy pieces, we have a host of ideas.