A Close Look at the Prusa i3 MK3

The Prusa i3 MK3 is, for lack of a better word, inescapable. Nearly every hacker or tech event that I’ve attended in 2018 has had dozens of them humming away, and you won’t get long looking up 3D printing on YouTube or discussion forums without somebody singing its praises. Demand for Prusa’s latest i3 printer is so high that there’s a literal waiting list to get one.

At the time of this writing, over a year after the printer was officially put up for sale, there’s still nearly a month lead time on the assembled version. Even longer if you want to wait on the upgraded powder coated bed, which has unfortunately turned out to be a considerable production bottleneck. But the team has finally caught up enough that the kit version of the printer (minus the powder coated bed) is currently in stock and shipping next day.

I thought this was a good a time as any to pull the trigger on the kit and see for myself what all the excitement is about. Now that I’ve had the Prusa i3 MK3 up and running for a couple of weeks, I can say with confidence that it’s not just hype. It isn’t a revolution in desktop 3D printing, but it’s absolutely an evolution, and almost certainly represents the shape of things to come for the next few years.

That said, it isn’t perfect. There’s still a few elements of the design that left me scratching my head a bit, and some parts of the assembly weren’t quite as smooth as the rest. I’ve put together some of those observations below. This isn’t meant to be a review of the Prusa i3 MK3 printer, there’s more than enough of those already, but hopefully these assorted notes may be of use to anyone thinking of jumping on the Prusa bandwagon now that production has started really ramping up.

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Memories Of A Mis-Spent Youth: Learnabout Simple Electronics

Heaven, for tech-inclined late-1970s British kids.
Heaven, for tech-inclined late-1970s British kids.

Early last spring, we featured a book review, as part of our occasional Books You Should Read series. Usually these are seminal tomes, those really useful books that stay with you for life and become well-thumbed, but in this case it was a children’s book. Making a Transistor Radio, by [George Dobbs, G3RJV], was a part of the long-running series of Ladybird books that educated, entertained, and enthralled mid-20th-century British kids, and its subject was the construction of a 3-transistor regenerative AM receiver. If you talk to a British electronic engineer of A Certain Age there is a good chance that this was the volume that first introduced them to their art, and they may even still have their prized radio somewhere.

Making a Transistor Radio was a success story, but what’s not so well-known is that there was a companion volume published a few years later in 1979. Simple Electronics was part of the imprint’s Learnabout series, and it took the basic premise of its predecessor away from the realm of radio into other transistor circuits. Transistor timers and multivibrators were covered, Morse code, and finally quite an ambitious project, an electronic organ.

Opening the book it is evident that there has been a slight cultural shift since the first volume was published. The typography is much more modern in feel, and the picture of the child experimenter on the inside of the cover is a photograph of a late-70s young girl in place of the 1950s-style boy wearing a tie building the radio. The practical nature of the writing hasn’t changed though, while it states that some of the background information is not being repeated from Making a Transistor Radio we are taken straight into the deep end with a section on the tools required to work with the series’ signature screw cup on wooden baseboard construction technique.

Construction was so much easier when transistors came with long leads.
Construction was so much easier when transistors came with long leads.

The original book used germanium transistors from the Mullard OC series, OC71s and an OC44. These were some of the earliest British transistors, and as I can attest from building my radio in that period, difficult to obtain by the late 1970s. This book has therefore moved on to a later design, the AC128. Still a germanium PNP device, but this time in a metal can and crucially still available at the time due to having been a part used in more than one mid-70s colour TV set. We’re given a no-nonsense introduction to the device, told about its package, pinout, and schematic diagram. It’s refreshing to see a children’s book in which the child is introduced to such an adult subject as this without being constantly reminded that they are a child.

We then spend a couple of pages looking at a transistor as a switch. A 10K base resistor is used to bias an AC128 with a flashlight bulb as its collector load, and with a flying lead to the negative supply (remember this is a PNP transistor!) the bulb can be turned on and off. In typical form, we’re shown how to make a bulb holder from a paper clip should we not be able to source a dedicated component. The basic switch is then extended with an electrolytic capacitor to make a simple time delay switch, and finally we’re shown how two such circuits combine to make an astable multivibrator and flash a pair of bulbs.

The astable multivibrator, explained for kids.
The astable multivibrator, explained for kids.

For me, circa 1979 or 1980, this was something of an earth-shattering moment. For the first time, I understood how an oscillator worked. That transistor turned on, triggering the other transistor after a delay, which in turn triggered the first transistor after a further delay, and so on and so on. It’s a simple enough circuit, but to a kid who had only recently been introduced to electronics, it was an amazing moment of revelation to have an insight into how it worked. It probably gave me a lifetime bad habit in that the two-transistor astable has become my go-to circuit when I need a quick and dirty square wave. They can be assembled from commonly desolderable scrap components on a bit of PCB or tinplate in a matter of minutes, and I have used them for nasty logic clocks, harmonic-rich signal sources, PWM oscillators, switching power supplies, and many more applications all because of this book.

Enough reminiscences, and time to turn the page. For a bit of fun we’re shown the light flasher as a robot with flashing eyes, before substituting some of the components and adding a crystal earpiece for an audio oscillator. This is the first part of the serious business of the book, because it forms the basis of all the following projects. It’s also the furthest I got with the book as a child, because of a lack of enough AC128s for the complete organ project, and a lack of aptitude for music. I was shown how to use a soldering iron, discovered that scrap TV sets in dumpsters contained a goldmine of parts, and never looked back.

[George Dobbs] is a radio amateur, so of course once he has a legion of British kids with audio oscillators he then leads them into making a Morse Code practice oscillator with a filter and a key made from tinplate. In typical no-nonsense style we’re introduced to amateur radio, code, and basic operating procedure. There are even instructions for making a two-station setup using three-core mains flex, how many kids who built that went on to have callsigns of their own?

The organ project awaits, but before then we have time for a couple more circuits to get used to varying the pitch of the oscillator. A “violin” using a potentiometer, and a photoelectric cell each get their own page, after which you have to wonder: how many kids managed to get their parents to shell out for that ORP12 CdS cell?

Never lose the fascination you gain from your first project!
Never lose the fascination you gain from your first project!

The organ is of the “Stylophone” variety, with notes picked out using a stylus over conductive pads on the keyboard. Skeleton preset potentiometers are used for tuning, with the alternative of filing notches in carbon resistors. This would not have been a cheap project at all on a pocket-money budget in 1979, did any readers build it? If they went for the final two pages, the same 1-transistor loudspeaker amplifier as that used in the transistor radio, and a vibrato circuit using a low-frequency version of the multivibrator, then pocket money would have been in very short supply indeed.

But to look at it this way probably misses the point of the book. Where the previous book was all about presenting a single project in stages, this one is more about teaching some basic transistor circuits in stages. When I was given a copy I had a basic idea about transistors from those OC71s in the radio, but when I’d read this one and built some of the circuits I had a much more varied grasp of solid-state electronics. I knew about RC circuits and oscillators, and the effect of changing the values of an RC circuit on frequency. Some of the things I learned from this book I still use today, and nearly a decade after reading it when I was a 1st year electronic engineering undergraduate I hit the ground running in our course on transistor circuits because of it.

Learnabout Simple Electronics has been out of print for well over three decades now, but if you want a copy you should be able to find it in second-hand book stores online. There’s also at least one PDF version available too, if all you want is a quick look.

DSO Nano 3 Review: a 20 MHz Pocket ‘Scope For Not A Lot

The oscilloscope is an essential tool of any electronics bench, and it is also an instrument whose capabilities have expanded exponentially over the decades. Your entirely analogue CRT ‘scope of a few decades ago has now been supplanted by a digital device that takes on many of the functions of both an expensive multimeter a frequency counter, and more. At the top end of the market the sky is the limit when it comes to budget, and the lower end stretches down to low-bandwidth devices based upon commodity microcontrollers for near-pocket-money prices.

These super-cheap ‘scopes are usually sold as kits, and despite their very low bandwidth are surprisingly capable instruments with a useful feature set due to well-written software. I  reviewed a typical model last year, and came away lamenting its lack of an internal battery and a decent quality probe. If only someone would produce an inexpensive miniature ‘scope with a decent bandwidth, decent probe, and an internal battery!

As it happens, I didn’t have long to wait for my wish to be satisfied, with news of the release of the DSO Nano 3. Let’s see what you can do with a portable scope for less than $50.

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Video Review: AND!XOR DEF CON 26 Badge

The AND!XOR team have somehow managed to outdo themselves once again this year. Their newest unofficial hardware badge for DEF CON 26 just arrived. It’s a delightful creation in hardware, software, and the interactive challenges built into both.

They call this the “Wild West of IoT”, a name that draws from the aesthetic as well as the badge-to-badge communications features. Built on the ESP32-WROVER module which brings both WiFi and Bluetooth to the party, the badges are designed to form a wireless botnet at the conference. Anyone with a badge can work to advance their level and take more and more control of the botnet as they do.

Check out the video overview and then join me below for a deeper dive into all this badge has to offer.

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Review: SMD Tweezer Meter or Tweezer Probes For Your Multimeter?

It’s remarkable how tiny electronics have become. Heaven knows what an old-timer whose experience started with tubes must think, to go from solder tags to SMD in a lifetime is some journey. Even  the generation that started with discrete transistors has lived through an incredible shift. But it’s true, SMD components are tiny, and that presents a challenge aside from the one you’ll face when soldering them. Identifying and measuring the value of a chip component too small to have any writing upon it becomes almost impossible with a pair of standard test probes.

Happily the test equipment manufacturers have risen to the challenge, and produced all sorts of meters designed for SMD work that have a pair of tweezers instead of test prods. When I was looking for one I did my usual thing when it comes to Hackaday reviews. I looked at the budget end of the market, and bought an inexpensive Chinese model for about £16($21). And since I was browsing tweezers I couldn’t resist adding another purchase to my order. I found a pair of tweezer test probes for my multimeter which cost me just over a pound ($1.30) and would provide a useful comparison. For working with SMD components in situ, do you even need the special meter?

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A Sneak Preview Of The Hacker Warehouse Badge

We were lucky enough to get our hands on a hand-soldered prototype of the new Hacker Warehouse badge, and boy is this one a treat. It’s fashionable, it’s blinky, and most impressively, it’s a very useful tool. This badge can replace the Google Authenticator two factor authentication app on your phone, and it’s a USB Rubber Ducky. It’s also a badge. Is this the year badges become useful? Check out the video below to find out more.

This is the time of year when hardware hackers from all across North America are busy working on the demoscene of hardware and manufacturing. This is badgelife, the celebration of manufacturing custom wearable electronics for one special weekend in Las Vegas. In just about a month from now, there will be thousands of independent badges flooding Caesar’s Palace in Vegas, complete with blinkies, custom chips, innovative manufacturing processes, and so many memes rendered in fiberglass and soldermask.

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Review: FG-100 DDS Function Generator

I don’t have a signal generator, or more specifically I don’t have a low frequency signal generator or a function generator. Recently this fact collided with my innocent pleasure in buying cheap stuff of sometimes questionable quality. A quick search of your favourite e-commerce site and vendor of voice-controlled internet appliances turned up an FG-100 low frequency 1Hz to 500kHz DDS function generator for only £15 ($21), what was not to like? I was sold, so placed my order and eagerly awaited the instrument’s arrival.

The missing function generator is a gap in the array of electronic test instruments on my bench, and it’s one that maybe isn’t as common a device as it once might have been. My RF needs are served by a venerable Advance signal generator from the 1960s, a lucky find years ago in the back room of Stewart of Reading, but at the bottom end of the spectrum my capabilities are meagre. So why do I need another bench tool?

It’s worth explaining what these devices are, and what their capabilities should be. In simple terms they create a variety of waveforms at a frequency and amplitude defined by their user. In general something described as a signal generator will only produce one waveform such as a sine or a square wave, while a function generator will produce a variety such as sine, square, and sawtooth waves. More accomplished function generators will also allow the production of arbitrary waveforms defined by the user. It is important that these instruments have some level of calibration both in terms of their frequency and the amplitude of their output. It is normal for the output to range from a small fraction of a volt to several volts. How would the FG-100 meet these requirements? Onward to my review of this curiously inexpensive offering.

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