If you are from the United States and of a certain age, it is very likely you owned some form of Commodore computer. Outside the US, that same demographic was likely to own an Amstrad. The Z80-based computers were well known for game playing. [Freemac] implemented a working Amstrad CPC6128 using a Xilinx FPGA on a NEXYS2 demo board.
The wiki posting is a bit long, but it covers how to duplicate the feat, and also gives technical details about the design. It also outlines the development process used ranging from starting with a simple Z80 emulation and moving on to more sophisticated attempts. You can see a video of the device below.
Sometimes we run into real problems restoring old machines. [RedruM69] recently ran into a system with a dead Real Time Clock (RTC) module. These modules were used on computers and all sorts of other equipment, storing time, date, and 100 or so bytes of battery backed SRAM (before the days of cheap, plentiful flash memory). Often an external coin cell would supply power to the module. In some cases though, cost savings would take over, and the battery would be incorporated into the module. Such is the case with many Dallas Semiconductor models, and the benchmarq bq3287 module [RedruM69] was working with. If we’re reading the date code right, the module was produced in mid 1995 so we’re well past the advertised 10 year battery life.
Apparently Texas Instruments is the current owner of this design, and they even have a datasheet online. (PDF link). It turns out that the bq3287 is a descendant of the bq3285, except that the battery pin is internally disconnected. For most people this would mean a search for a compatible replacement. An industrious hacker might even whip up something compatible from modern components. Not [RedruM69] though. He broke out his Dremel tool and cut into the potted case. Exposing the internal connections above pins 16 and 20 allowed him to solder two wires on. Connecting these wires to an external coin cell brought the module back to life.
[RedruM69] isn’t the first one to perform this hack. Sun computers kept their MAC address in chips like this. When the battery went dead, the computer was off the network. Hackers have been cutting the modules open and adding batteries for years. You could always forgo RTC modules completely and use the power grid as your timebase.
Like so many other home appliances, it’s likely that even your air conditioner has a serial interface buried inside it. If you’re wondering why, it’s because virtually every microcontroller on the planet has a UART built in, and it’s highly useful for debugging during the development process, so it makes sense to use it. Thus, it was only a matter of time before we saw a hacked airconditioner controlled by a Raspberry Pi.
[Hadley] was growing frustrated with the IR remote for his Mitsubishi air conditioner; it can issue commands, but it’s a one way interface – there’s no feedback on current status or whether commands are received, other then the occasional beep or two. Deciding there had to be a better way, [Hadley] grabbed a Saleae Logic Analyser and started probing around, determining that the unit spoke 5 V TTL at 2400 bps with even parity. The next step was to start talking back.
WiFi and Bluetooth were never meant to be the radios used by a billion Internet of Things hats, umbrellas, irrigation systems, or any other device that makes a worldwide network of things interesting. The best radio for IoT is something lightweight which operates in the sub-Gigahertz range, doesn’t need a lot of bandwidth, and doesn’t suck down the power like WiFi. For the last few years, a new low-power wireless communication standard has been coming on the scene, and now this protocol — LoRa — will soon be available in an Arduino form factor.
The Primo, and NRF
It’s not LoRa, but the Arduino Primo line is based on the ESP8266 WiFi chip and a Nordic nRF52832 for Bluetooth. The Primo comes in the ever-familiar Arduino form factor, but it isn’t meant to be an ‘Internet of Things’ device. Instead, it’s a microcontroller for devices that need to be on the Internet.
Also on display at CES this year is the Primo Core which we first saw at BAMF back in May. It’s a board barely larger than a US quarter that has a few tricks up its sleeve. The Primo Core is built around the nRF52832, and adds humidity, temperature, 3-axis magnetometer and a 3-axis accelerometer to a square inch of fiberglass.
The Primo Core has a few mechanical tricks up its sleeve. Those castellated pins around the circumference can be soldered to the Alice Pad, a breakout board that adds a USB port and LiPo battery charger.
LoRa
Also on deck at the Arduino suite were two LoRa shields. In collobration with Semtech, Arduino will be releasing the pair of LoRa shields later this year. The first, the Node Shield, is about as simple as it can get — it’s simply a shield with a LoRa radio and a few connectors. The second, the Gateway Shield, does what it says on the tin: it’s designed to be a gateway from other Arduino devices (Ethernet or WiFi, for example) to a Node shield. The boards weren’t completely populated, but from what I could see, the Gateway shield is significantly more capable with support for a GPS chipset and antenna.
A partnership with Cayenne and MyDevices
Of course, the Internet of Things is worthless if you can’t manage it easily. Arduino has struck up a partnership with MyDevices to turn a bunch of low-bandwidth radio and serial connections into something easy to use. Already, we’ve seen a few builds and projects using MyDevices, but the demos I was shown were extremely easy to understand, even if there were far too many devices in the room.
All of this is great news if you’re working on the next great Internet of Things thing. The Primo Core is one of the smallest wireless microcontroller devices I’ve seen, and the addition of LoRa Arduino shields means we may actually see useful low-bandwidth networks in the very near future.
This is the continuation of a series of posts where I create a schematic and PCB in various EDA tools. Already, we’ve looked at Eagle CAD, KiCad, and took a walk down memory lane with one of the first PCB design tools for the IBM PC with Protel Autotrax. One of the more controversial of these tutorials was my post on Fritzing. Fritzing is a terrible tool that you should not use, but before I get to that, I need to back up and explain what this series of posts is all about.
The introduction to this series of posts laid it out pretty bare. For each post in this series, I will take a reference schematic for a small, USB-enabled ATtiny85 development board. I recreate the schematic, recreate the board, and build a new symbol and footprint in each piece of software. That last part — making a new symbol and footprint — is a point of contention for Fritzing users. You cannot create a completely new part in Fritzing. That’s a quote straight from the devs. For a PCB design tool, it’s a baffling decision, and I don’t know if I can call Fritzing a PCB design tool now.
Coming in at 125 cubic centimeters displacement, [Keith Harlow]’s fuel injected masterpiece isn’t too far from the size of some motor scooter engines. We doubt the local Vespa club would look upon it as legit mod, but we’d love to see it. [Keith]’s build log is a long series of forum posts, but from what we’ve seen it looks like every part was made by hand with the exception of the fuel injection system. Even the caps for the spark plugs were custom injection molded right in [Keith]’s shop. And it appears that no CNC was used – even those intake headers and the rotors for the supercharger were hogged out of aluminum using a manual mill. The exhaust headers alone are straight up works of art. There’s a staggering amount of work here, which begs the question: why? The answer in this case is obviously, “Because he can.”
Few builds compare to the level of craftsmanship on display here. The Clickspring skeleton clock comes to mind, but for model engine builds we’d have to point to [Keith]’s earlier 1/4-scale V8 engine. And we’ll hasten to add that as much time as [Keith] has spent building these works of mechanical art, he’s probably dedicated just as much time to documenting them and giving back to his community. We can all learn a lesson from that.
Normally, when something explodes it tends to be a bad day for all involved. But not every explosion is intended to maim or kill. Plenty of explosions are designed to save lives every day, from the highway to the cockpit to the power grid. Let’s look at some of these pyrotechnic wonders and how they keep us safe.
Explosive Bolts
The first I can recall hearing the term explosive bolts was in relation to the saturation TV coverage of the Apollo launches in the late 60s and early 70s. Explosive bolts seemed to be everywhere, releasing umbilicals and restraining the Saturn V launch stack on the pad. Young me pictured literal bolts machined from solid blocks of explosive and secretly hoped there was a section for them in the hardware store so I could have a little fun.
Pyrotechnic fasteners are mechanical fasteners (bolts, studs, nuts, etc.) that are designed to fail in a predictable fashion due to the detonation of an associated pyrotechnic device. Not only must they fail predictably, but they also have to be strong enough to resist the forces they will experience before failure is initiated. Failure is also typically rapid and clean, meaning that no debris is left to interfere with the parts that were previously held together by the fastener. And finally, the explosive failure can’t cause any collateral damage to the fastened parts or nearby structures.
Pyrotechnic fasteners fall into two broad categories. Explosive bolts look much like regular bolts, and are machined out of the same materials you’d expect to find any bolt made of. The explosive charge is usually internal to the shank of the bolt with an initiating device of some sort in the head. To ensure clean, predictable separation, there’s a groove machined into the bolt to create a shear plane.
Frangible nuts are another type of pyrotechnic fastener. These tend to be used for larger load applications, like holding down rockets. Frangible nuts usually have two smaller threaded holes adjacent to the main fastener thread; pyrotechnic booster charges split the nut across the plane formed by the threaded holes to release the fastener cleanly.
“Eject! Eject! Eject!”
Holding back missiles is one thing, but where pyrotechnic fasteners save the most lives might be in the cockpits of fighter jets around the world. When things go wrong in a fighter, pilots need to get out in a hurry. Strapping into a fighter cockpit is literally sitting on top of a rocket and being surrounded by explosives. Most current seats are zero-zero designs — usable at zero airspeed and zero altitude — that propel the seat and pilot out of the aircraft on a small rocket high enough that the parachute can deploy before the pilot hits the surface. Dozens of explosive charges take care of ripping the aircraft canopy apart, deploying the chute, and cutting the seat free from the parachuting pilot, typically unconscious and a couple of inches shorter from spinal disc compression after his one second rocket ride.
There’s little doubt that airbags have saved countless lives since they’ve become standard equipment in cars and trucks. When you get into a modern vehicle, you are literally surrounded by airbags — steering wheel, dashboard, knee bolsters, side curtains, seatbelt bags, and even the rear seat passenger bags. And each one of these devices is a small bomb waiting to explode to save your life.
When we think of explosives we tend to think of substances that can undergo rapid oxidation with subsequent expansion of hot gasses. By this definition, airbag inflators aren’t really explosives, since they are powered by the rapid chemical decomposition of nitrogenous compounds, commonly sodium azide in the presence of potassium nitrate and silicon dioxide. But the difference is purely academic; anyone who has ever had an airbag deploy in front of them or watched any of the “hold my beer and watch this” airbag prank video compilations will attest to the explosive power held in that disc of chemicals.
When a collision is detected by sensors connected to the airbag control unit (ACU), current is applied to an electric match, similar to the engine igniters used in model rocketry, buried within the inflator module. The match reaches 300°C within a few milliseconds, causing the sodium azide to rapidly decompose into nitrogen gas and sodium. Subsequent reactions mop up the reactive byproducts to produce inert silicate glasses and add a little more nitrogen to the mix. The entire reaction is complete in about 40 milliseconds, and the airbags inflate fully within 80 milliseconds, only to deflate again almost instantly through vent holes in the back of the bag. By the time you perceive that you were in an accident, the bag hangs limply from the steering wheel and with any luck, you get to walk away from the accident.
Grid Down
We’ve covered a little about utility poles and all the fascinating bits of gear that hang off them. One of the pieces of safety gear that lives in the “supply space” at the top of the poles is the fuse cutout, or explosive disconnector. This too is a place where a small explosion can save lives — not only by protecting line workers but also by preventing a short circuit from causing a fire.
Cutouts are more than just fuses, though. Given the nature of the AC transmission and distribution grid, the lines that cutouts protect are at pretty high voltages of 11 kV or more. That much voltage means the potential for sustained arcing if contacts aren’t rapidly separated; the resulting plasma can do just as much if not more damage than the short circuit. So a small explosive cartridge is used to rapidly kick the fuse body of a cutout out of the frame and break the circuit as quickly as possible. Arc suppression features are also built into the cutout to interrupt the arc before it gets a chance to form.
[Big Clive] recently did a teardown of another piece of line safety gear, an 11 kV lightning arrestor with an explosive disconnector. With a Dremel tool and a good dose of liquid courage, he liberated a carbon slug from within the disconnector, which when heated by a line fault ignites a .22 caliber charge similar to those used with powder actuated fastener tools. The rapid expansion of gasses ruptures the cases of the disconnector and rapidly breaks the circuit.
Conclusion
We’ve covered a few of the many ways that the power of expanding gas can be used in life safety applications. There are other ways, too — snuffing out oil field fires comes to mind, as does controlled demolition of buildings. But the number of explosives protecting us from more common accidents is quite amazing, all the more so when you realize how well engineered they are. After all, these everyday bombs aren’t generally blowing up without good reason.
