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Remoticon 2021 // Rob Weinstein Builds An HP-35 From The Patent Up

April 7, 2022 by 40 Comments

Fifty years ago, Hewlett-Packard introduced the first handheld scientific calculator, the HP-35. It was quite the engineering feat, since equivalent machines of the day were bulky desktop affairs, if not rack-mounted. [Rob Weinstein] has long been a fan of HP calculators, and used an HP-41C for many years until it wore out. Since then he gradually developed a curiosity about these old calculators and what made them tick. The more he read, the more engrossed he became. [Rob] eventually decided to embark on a three year long reverse-engineer journey that culminated a recreation of the original design on a protoboard that operates exactly like the original from 1972 (although not quite pocket-sized). In this presentation he walks us through the history of the calculator design and his efforts in understanding and eventually replicating it using modern FPGAs.

The HP patent ( US Patent 4,001,569 ) contains an extremely detailed explanation of the calculator in nearly every aspect. There are many novel concepts in the design, and [Rob] delves into two of them in his presentation. Early LED devices were a drain on batteries, and HP engineers came up with a clever solution. In a complex orchestra of multiplexed switches, they steered current through inductors and LED segments, storing energy temporarily and eliminating the need for inefficient dropping resistors. But even more complicated is the serial processor architecture of the calculator. The first microprocessors were not available when HP started this design, so the entire processor was done at the gate level. Everything operates on 56-bit registers which are constantly circulating around in circular shift registers. [Rob] has really done his homework here, carefully studying each section of the design in great depth, drawing upon old documents and books when available, and making his own material when not. For example, in the course of figuring everything out, [Rob] prepared 338 pages of timing charts in addition to those in the patent. Continue reading “Remoticon 2021 // Rob Weinstein Builds An HP-35 From The Patent Up” →

Just What On Earth Is A Therm?

April 7, 2022 by 86 Comments

With the news here in Europe full of the effect of the war in Ukraine on gas supplies and consequently, prices, there it was on the radio news: a unit of measurement so uniquely British that nobody uses it in the real world and nobody even has a clue what it really means. We’re speaking of the Therm, one of those words from our grandparents’ era of coal gas powered Belling cookers and Geyser water heaters hanging over the bath, which has somehow hung on in the popular imagination as a mysterious unit of domestic gas referred to only in the mass market news media. What on earth is a therm, and why are we still hearing it on the news in the UK?

You can’t Buy A Therm

Asking the internet what a therm is reveals the answer, it’s 100,000 BTU. What’s a BTU? A British Thermal Unit, another anachronistic measurement five decades after the UK went metric, it’s the amount of energy required to raise a pound of water by a degree Fahrenheit. Which in turn is about 1,054 joules, in today’s measurements. So a therm is thus a unit of energy, can we take a look at our gas meters and see how many of them we’ve used this winter? Not so fast, because gas isn’t sold by the therm. Older gas meters had cubic feet on them, and we’re guessing that now they’re calibrated in cubic meters. We can’t even buy a therm of gas, so why on earth are the British media still using it? Continue reading “Just What On Earth Is A Therm?” →

Whales Help Scientists Investigate The Mystery Of Menopause

April 6, 2022 by 7 Comments

Menopause is the time of life when menstrual periods come to a halt, and a woman is no longer able to bear children. The most obvious cause of menopause is when the ovaries run out of eggs, though it can also be caused by a variety of other medical processes. While menopause is in many ways well-understood, the biological reason for menopause, or the way in which it evolved in humanity remains a mystery. The process was once thought to be virtually non-existent in the animal kingdom, raising further questions.

Surprisingly recently, however, scientists began to learn that humans are not alone in this trait. Indeed, a small handful of sea-going mammals also go through this unique and puzzling process.

Continue reading “Whales Help Scientists Investigate The Mystery Of Menopause” →

Bath County Pumped Storage Station (Credit: CHA)

Grid-Level Energy Storage And The Challenge Of Storing Energy Efficiently

April 6, 2022 by 118 Comments

Although every electrical grid begins with the production of electricity, there are times when storing this power in some form instead of using it immediately is highly convenient. Today’s battery-powered gadgets are an obvious example of such time-shifting, but energy storage plays a major role on the grid itself, too, whether in electrochemical, mechanical or in some other form.

Utility-level energy storage is essential for not only stabilizing the grid, but also to time-shift excess energy and provide a way to deal with sudden spikes in demand (peak-shaving) plus demand drops by absorbing the excess energy. The health of the grid can essentially be regarded as a function of its alternating current (AC) frequency, with strong deviations potentially leading to a collapse of the grid.

Naturally, such energy storage is not free, and the benefits of adding it to the grid have to be considered against the expense, as well as potential alternatives. With the rapid increase of highly volatile electrical generators on the grid in the form of non-dispatchable variable renewable energy, e.g. wind turbines and PV solar, there has been a push to store more excess power rather than curtailing it, in addition to using energy storage for general grid health.

Continue reading “Grid-Level Energy Storage And The Challenge Of Storing Energy Efficiently” →

Magpies Help Each Other Escape Tracking Devices With This One Weird Trick

April 5, 2022 by 19 Comments

Scientists who work with animals love to track their movements. This can provide interesting insights on everything from mating behaviour, food sources, and even the way animals behave socially – or anti-socially, as the case may be.

This is normally achieved with the use of tracking devices, affixed to an animal so that it can be observed remotely while going about its normal business. However, Australian scientists have recently run into some issues in this area, as the very animals they try to track have been removing these very devices, revealing some thought-provoking behaviour in the process.

Continue reading “Magpies Help Each Other Escape Tracking Devices With This One Weird Trick” →

Hacker Dictionary: RS-485 Will Go The Distance

April 5, 2022 by 59 Comments

RS485 is a communication standard that should be part of the advanced hardware hacker’s arsenal; it’s not commonly encountered, but powerful exactly when you need it. It’s a physical layer interface for wired communications that uses a single differential pair for noise immunity, has good long-distance properties, and allows many connections to a single bus. Because of that, you will encounter it in security systems and even cameras, wired sensor networks, DMX512 lighting and all sorts of industrial electronics. For our hobbyist goals, you can absolutely use RS485 to build your home (or room) automation system, or a relatively large robot – without all those worries that wireless brings.

The name might remind you of RS232, and that’s because both RS232 and RS485 are standards that come from EIA (Electronics Industries Alliance). It also might remind you of RS422, if you’ve ever seen this name mentioned online – RS422 and RS485 are closely intertwined, sharing most of the physical layer, and I’ll show how exactly they relate. Continue reading “Hacker Dictionary: RS-485 Will Go The Distance” →

Confessions Of A Crimpoholic

April 4, 2022 by 80 Comments

Hi, my name is Dan and I’m a crimpoholic.

Honestly, I didn’t know I was a serial abuser of crimping tools until this weekend. I’ve been working on a small solar power system, and on Saturday I found myself struggling to get the BMS installed on the battery. I bought a Bluetooth dongle to connect the BMS to a smartphone app for checking the individual cells of the battery. I assumed it would just plug right into the UART port on the BMS, but alas — different connectors. So off I went to my bench, looking for a sensible way to make the connection.

My first thought was to simply log the connector off the dongle and solder the leads to the traces on the PCB right below the UART port. But then I saw that the pins in the port looked like 0.1″ pitch, so I rummaged through my stash to see what I could find. To my surprise, I had not only a kit of 0.1″ female crimps and housings, but I also had the crimping tool for them! I had no memory of making the purchase, but I thanked my lucky stars that I did, and got on with the job.

Continue reading “Confessions Of A Crimpoholic” →