See Who’s Calling with Caller Pi-D

One of the hardest things in life is watching your parents grow old. As their senses fail, the simplest things become difficult or even impossible for them to do.

[kjepper]’s mom is slowly losing her sight. As a result, it’s hard for her to see things like the readout on the caller ID. Sure, there are plenty of units and phones she could get that have text-to-speech capabilities, but the audio on those things is usually pretty garbled. And yes, a smartphone can natively display a picture of the person calling, but [kjepper]’s mom isn’t technologically savvy and doesn’t need everything else that comes with a smartphone. What she needs is a really simple interface which makes it clear who’s calling.

Initially, [kjepper] tried to capture the caller ID data using only a USB modem. But for whatever reason, it didn’t work until he added an FSKDTMF converter between the modem and the Pi. He wrote some Node.js in order to communicate with the Pi and send the information to the screen, which can display up to four calls at once.  To make a mom-friendly interface, he stripped an old optical mouse down to the scroll wheel and encased it in wood. Mom can spin the wheel to wake the system up from standby, and click it to mark the calls as read. Now whenever Aunt Judy calls the landline, it’s immediately obvious that it’s her and not some telemarketer.

[via r/DIY]

How Analog Tide Predictors Changed Human History

If you’re completely landlocked like I am, you may dream of ocean waves lapping at the shore, but you probably don’t think much about the tides. The movement of the ocean tides is actually quite important to many groups of people, from fishermen to surfers to coastal zone engineers. The behavior of the tides over time is helpful data for those who study world climate change.

Early tide prediction was based on observed changes in relation to the phases of the Moon. These days, tide-predicting is done quickly and with digital computers. But the first purpose-built machines were slow yet accurate analog computation devices that, as they were developed, could account for increasing numbers of tidal constituents, which represent the changes in the positions of tide-generating astronomical bodies. One of these calculating marvels even saved the Allies’ invasion of Normandy—or D-Day— in World War II.

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The Conductive Paper That Sparked a Revolution

Legendary electrical engineer and linear IC trailblazer Bob Widlar was just like you. What I mean is that he would use everything available to him to mock up circuits, create prototypes, and make things work. One of the simplest and coolest tools he used was a conductive paper called Teledeltos. This wonderful stuff allowed him to define and test various configurations for the oddly-shaped ballast resistors he used in some of his high-performance circuit designs. But it wasn’t created for people like you and Bob. Teledeltos paper was created and trademarked by communications giant Western Union to drastically improve the convenience of telegrams.

Development of the electric telegraph ushered in the era of global communication. Suddenly, people could send messages to the other side of the world in a fraction of the time it took by post. The telegraph absolutely revolutionized human communication. It was the e-mail and the Twitter of its time. The telegraph’s efficiency made the Pony Express pretty much obsolete by the 1860s. And for a very long time it was much cheaper for people to send a telegram than make a long-distance phone call.

The Advantages of Facsimile

Translated from ancient Greek, ‘teledeltos’ basically means writing tablet at a distance. Western Union began developing Teledeltos paper in the 1930s for the purpose of transmitting telegrams by facsimile, a method that would greatly reduce the time it took to input messages into the system and get them out on the other side. As long as both the sender and the receiver had facsimile machines, a handwritten telegram could be transmitted without having to be typed by a clerk or translated into code. Teledeltos paper was also used in a variety of chart recorders, like seismographs and map plotters. The ability to feed a handwritten message, a photograph, or a map of enemy territory into a machine that transmitted an exact copy was a real game changer.

Because of its composition, Teledeltos paper could be easily marked without an electrolyte. It marked so well that photographs and other graphic information could be transmitted, and no processing was required on the receiving end. A dry recording paper is also much less sensitive to light and to temperature extremes. More importantly, properly stored dry paper is impervious to fungal growth. Teledeltos paper could sit around indefinitely without becoming useless. The only real disadvantage to this type of paper was the somewhat laborious process that went into achieving the desired resistance. Fax machines eventually moved on to digital transmission and thermal printing technology.

Image credit: MIT

Sparking a Revolution

Teledeltos paper has a light gray electro-sensitive coating on one side, and the other side is carbon black. When a current is applied with a stylus to the coated side of the paper, the coating is instantly burned away, revealing the carbon black. Teledeltos paper could be marked using either AC or DC. Polarity didn’t matter, either, but the boys in the lab at Western Union had better luck when they used a positive stylus with DC rather than a negative one.

Teledeltos paper was made in two types—“L” for low resistance and “H” for high. The resistivity of a roll of Teledeltos paper depended on the quality of the conductive fibers that went into it. The paper’s electrical characteristics were also influenced by the fiber beating process and the distribution of the conductive fibers by the supercalender, a system of hard rollers used in papermaking and other processes that press and smooth paper and other materials to increase the density.

Teledeltos to the Rescue

The Western Union Telecar printed telegrams on the go and delivered them to homes and businesses.
The Western Union Telecar printed telegrams on the go and delivered them to homes and businesses. Image credit: Modern Mechanix

Western Union was eager to extend its reach into private businesses and public places so that patrons who weren’t heavy telegram users didn’t have to visit a telegram office in order to share a bit of good news or to send their condolences. The company’s Telefax division came up with several types of machines to serve different business needs.

Some messages continued to be delivered by hand, but they weren’t printed at the central office. Western Union created a Telecar service to print telegrams transmitted to the car by the central office and deliver them to people’s homes. Messages were printed onto recording blanks that were cut automatically by a Telefax recorder situated in the car’s passenger area. The Telecar’s radio and amplification equipment was in the trunk.

The standard Telefax machine for office use was fairly large, like an early microwave oven. A smaller version called the DeskFax was only about the size of a breadbox, and these units occupied the desks of many businessmen and secretaries because of their convenience.

A Western Union DeskFax unit. Image from [B. Hilpert]
A Western Union DeskFax unit. Image from [B. Hilpert]
Both the Telefax and the DeskFax scanned and recorded telegrams using a rotary drum mechanism. A message could either be typed or handwritten onto a telegram blank. The sender then wrapped the telegram around a drum and set the machine to send. The machine would scan the message optically and then transmit it to the central office.

Before sending it on to the recipient, an attendant at the telegram office had to remove the incoming message and wrap it around the drum of a transmitting machine. Once connected to the receiving party’s line, the far end unit would buzz to arouse attention. The receiving patron would then load a blank on to their DeskFax’s roller and set their machine to receive.

Teledeltos for Hacking and Education

Measuring potential differences. Image from
Measuring potential differences.
Image from UCSD

Conductive paper like Teledeltos has many applications aside from fax machines and Fathometers. For starters, it’s great for making one-offs of both standard and variable resistors. Conductive paint can be used as connection points for wires. The paper is also well-suited for simulating current flow through circuits using a fraction of the current intended in production. Vacuum tube designers used Teledeltos for modeling potentials. Teledeltos can also be used to visualize electromagnetic potentials and perform field plotting.

We’re sure that at least a few of our readers out there used Teledeltos or something like it in school or on the job. Did you know you can still buy it? Teledeltos paper itself is still available from two companies in the UK, Better Equipped and Timstar. In the US, you can get it from Pasco in packs of 50 and 100 sheets, with and without a grid pattern.

[Teledeltos paper image is a product photo from Better Equipped]

Hackaday’s Omaha Mini Maker Faire Roundup

The 2nd annual Omaha Mini Maker Faire wasn’t our first rodeo, but it was nonetheless a bit surprising . Before we even made it inside to pay our admission to the Omaha Children’s Museum, I took the opportunity to pet a Transylvanian Naked Neck chicken at one of the outdoor booths. The amiable fowl lives at City Sprouts, an Omaha community farming collective in its 20th year of operation. There seemed to be a theme of bootstrappy sustainability among the makers this year, and that’s great to see.

Just a few feet away sat a mustard-colored 1975 Chevy pickup with a food garden growing in its bed. This is Omaha’s truck farm, an initiative that seeks to educate the city’s kids in the ways of eating locally and growing food at home.  On a carnivorous note, [Chad] from Cure Cooking showed my companion and me the correct way to dry-cure meats using time-honored methods.

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Retrotechtacular: Weston Electrical Instruments

A ‘meter is one of the most important tools on any electronics bench. After you’ve exhausted your five senses trying to figure out what’s happening in a circuit, firing up the old ‘meter is usually the next step. Meters are largely digital nowadays, but their analog ancestors are still widely available. We have a chemist and inventor named [Edward Weston] to thank for the portability and ubiquity of DC measuring equipment.

After immigrating to the United States from England with the degree in medicine his parents wanted him to earn, [Edward Weston] asserted that he was more interested in chemistry. His career began in electroplating, where he soon realized that he needed a reliable, constant current source to do quality plating. This intense interest in power generation led him to develop a saturated cadmium cell, which is known as the Weston cell. Its chemistry produces a voltage stable enough to be used for meter calibration. The Weston cell is also good for making EMF determinations.

Within a few years, he co-founded the Weston Electrical Instrument Corporation. The company produced several types of meters along with transformers and transducers known for their portability and accuracy. In 1920, [Weston & Co.] created this 1920 educational film in cooperation with the United States Navy as part of a series on the principles of electricity.

The viewer is invited to consider the importance of measurement to civilization, most notably those fundamental measurements of length, mass, and time. [Weston] positions his electrical measuring instruments at this level, touting them as the international favorite. We get the full tour of a Weston meter, from the magnet treated for permanence to the specially designed pole pieces that correctly distribute lines of magnetic force. What education film about electromagnetism would be complete without an iron filings demonstration? This one definitely delivers.

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Omaha Mini Maker Faire: Recycle All the Things

A young maker named [Allie] drew a lot of attention at the 2nd annual Omaha Mini Maker Faire. Her booth was full of the various creations she has designed and built herself throughout the course of her short life. The biggest draw was her green design dollhouse, which focuses on environmentally friendly living. With the exception of the LEDs lighting the interior, some tape, and the requisite bit of hot glue, the entire structure and its contents were made from recycled materials.

green-dollhouse-thumbThe cardboard structure features a kitchen, living room, bedroom, bathroom, and attic. Every piece of furniture and all the decorations are made from salvaged materials and packaging. One side of the roof holds a Snap Circuits board with a solar panel that powers some blue LEDs on the bedroom wall. [Allie] poured water down the other side of the roof to demonstrate the rain water collection system. The house’s rain barrel was made from a grated parmesan cheese container, which is perfectly designed for the airline tubing running into it from the recycled plastic guttering.

owl-says-noOne of [Allie]’s other projects is a disagreeable owl fashioned from cardboard and a salvaged canister. Hidden away beneath the owl’s platform lies a simple gear system attached to a key on the front. Turning the key causes the owl’s head to swivel back and forth. We tried to make it spin all the way around, but the full range of motion is about 270 degrees. She also brought Mountain Dew, a hummingbird model made from a spark plug and other metal bits and bobs, including a pair of soda can wings.

mountain-dew-hummingbirdIn addition to her crafty skills, [Allie] is one well-spoken tween. She was more than happy to discuss her creations in detail to anyone who would listen, which included at least two local journalists and this impressed reporter. We learned through a bit of light research that a robot [Allie] built a few years ago inspired a British toy company to produce a new doll, the Robot Girl Lottie. She’s an inspiration to makers of all ages.

FERMIAC: The Computer that Advanced Beyond the Manhattan Project

One of the keys to nuclear fission is sustaining a chain reaction. A slow chain reaction can provide clean power for a city, and a fast one can be used to create a weapon that will obliterate a city. These days, kids can learn about Uranium and Plutonium in high school. But just a few generations ago, the idea of splitting the atom was just a lofty goal for the brightest physicists and mathematicians who gathered at Los Alamos National Laboratory under the Manhattan Project.

Decoding the mysteries of nuclear fission required a great deal of experimentation and calculations. One bright physicist in particular made great strides on both fronts. That man was [Enrico Fermi], one of the fathers of the atomic bomb. Perhaps his greatest contribution to moving the research beyond the Manhattan Project was creating a handheld analog computer to do the math for him. This computational marvel is known as the FERMIAC.

What is Fission?

Nuclear fission occurs when a nucleus is split into fragments, a process that unleashes a great deal of energy.  As a handful of neutrons travel through a reactor pile or other fissionable material, a couple of outcomes are possible. Any one neutron collision might result in fission. This means there will be some number of new neutrons whose paths must be tracked. If fission does not occur, the neutrons may simply scatter about upon collision, which changes their speed and trajectory. Some of the neutrons might be absorbed by the material, and others will simply escape it. All of these possibilities depend on the makeup of the material being bombarded and the speed of the neutron.

Fission Diagram by Michalsmid

Every event that happens to a neutron comprises its genealogical history. If this history is recorded and analyzed, a statistical picture starts to emerge that provides an accurate depiction of the fissility of a given material. [Fermi]’s computer facilitated the creation of such a picture by performing mathematical grunt work of testing different materials. It identified which materials were most likely to sustain a reaction.

Before he left Italy and the looming threat of fascism, [Fermi] led a group of young scientists in Rome called the Via Panisperna boys. This group, which included future Los Alamos physicist [Emilio Segrè], ran many experiments in neutron transport. Their research proved that slow neutrons are much better candidates for fission than fast neutrons.

During these experiments, [Fermi] ran through the periodic table, determined to artificially irradiate every element until he got lucky. He never published anything regarding his methods for calculating the outcomes of neutron collisions. But when he got to Los Alamos, [Fermi] found that [Stanislaw Ulam] had also concluded that the same type of repeated random sampling was the key to building an atomic weapon.

The Monte Carlo Method: Shall We Play a Game?

Monte Carlo method applied to approximating the value of π. by CaitlinJo

[Ulam], a Polish-born mathematician who came to the US in 1935, developed his opinion about random sampling due to an illness. While recuperating from encephalitis he played game after game of solitaire. One day, he wondered at the probability of winning any one hand as laid out and how best to calculate this probability. He believed that if he ran through enough games and kept track of the wins, the data would form a suitable and representative sample for modeling his chances of winning. Almost immediately, [Ulam] began to mentally apply this method to problems in physics, and proposed his ideas (PDF) to physicist and fellow mathematician [John von Neumann].

This top-secret method needed a code name. Another Los Alamos player, [Nick Metropolis] suggested ‘Monte Carlo’ in a nod to games of chance. He knew that [Ulam] had an uncle with a propensity for gambling who would often borrow money from relatives, saying that he just had to go to Monte Carlo. The game was on.

The Tricky Math of Fission

Determination of the elements most suitable for fission required a lot of calculations. Fission itself had already been achieved before the start of the Manhattan Project. But the goal at Los Alamos was a controlled, high-energy type of fission suitable for weaponization. The math of fission is complicated largely because of the sheer number of neutrons that must be tracked in order to determine the likelihood and speed of a chain reaction. There are so many variables involved that the task is monumental for a human mathematician.

[Stanislaw Ulam] and FERMIAC.

After [Ulam] and [von Neumann] had verified the legitimacy of the Monte Carlo method with regard to the creation of nuclear weaponry, they decided that these types of calculations would be a great job for ENIAC — a very early general purpose computer. This was a more intensive task than the one it was made to do: compute artillery firing tables all day and night. One problem was that the huge, lumbering machine was scheduled to be moved from Philadelphia to the Ballistics Research Lab in Maryland, which meant a long period of downtime.

While the boys at Los Alamos waited for ENIAC to be operational again, [Enrico Fermi] developed the idea forego ENIAC and create a small device that could run Monte Carlo simulations instead. He enlisted his colleague [Percy King] to build the machine. Their creation was built from joint Army-Navy cast off components, and in a nod to that great computer he dubbed it FERMIAC.

FERMIAC: Hacking Probabilities

FERMIAC was created to alleviate the necessity of tedious calculations required by the study of neutron transport. This is something of an end-run around brute force. It’s made mostly of brass and resembles a trolley car. In order to use it, several adjustable drums are set using pseudorandom numbers. One of these numbers represents the material being traversed. A random choice is made between fast and slow neutrons. A second digit is chosen to represent the direction of neutron travel, and a third number indicates the distance traveled to the next collision.

FERMIAC in use
FERMIAC in action.

Once these settings are dialed in, the device is physically driven across a 2-D scale drawing of the nuclear reactor or materials being tested. As it goes along, it plots the paths of neutrons through various materials by marking a line on the drawing. Whenever a material boundary is crossed, the appropriate drum is adjusted to represent a new pseudorandom digit.

FERMIAC was only used for about two years before it was completely supplanted by ENIAC. But it was an excellent stopgap that allowed the Manhattan Project to not only continue unabated, but with rapid progress. FERMIAC is currently on display at the Bradbury Science Museum in Los Alamos, New Mexico alongside replicas of Fat Man and Little Boy, the weapons it helped bring to fruition. [Fermi]’s legacy is cemented as one of the fathers of the atomic bomb. But creating FERMIAC cements his legacy as a hacker, too.

After Los Alamos, [Stanislaw Ulam] would continue to make history in the field of nuclear physics. [Enrico Fermi] was opposed to participating in the creation of the exponentially more powerful hydrogen bomb, but [Ulam] accepted the challenge. He proved that Manhattan Project leader [Edward Teller]’s original design was unfeasible. The two men worked together and by 1951 had designed the Teller-Ulam method. This design became the basis for modern thermonuclear weaponry.

Today, the Monte Carlo method is used across many fields to describe systems through randomness and statistics. Many applications for this type of statistical modeling present themselves in fields where probabilities are concerned, like finance, risk assessment, and modeling the universe. Wherever the calculation of all possibilities isn’t feasible, the Monte Carlo method can usually be found.

[Main Image Source: FERMIAC machine by Mark Pellegrini]

UPDATE: Commentor [lwatchdr] pointed out that the use of the FERMIAC began after the Manhattan Project had officially ended in 1946. Although many of the same people were involved, this analog computer wasn’t put into use until about a year later.