A Super UPS For The Pi

November 5, 2020 by Al Williams 57 Comments

One of the problems with using a Raspberry Pi or most other systems in a production environment is dealing with sudden shutdowns due to power loss. Modern operating systems often keep data in memory that should be on disk, and a sudden power cycle can create problems. One answer is an uninterruptible power supply, but maintaining batteries is no fun. [Scott] wanted to do better, so he built a UPS using supercapacitors.

A supercapacitor UPS is nearly ideal. The caps charge quickly and don’t wear out as a battery does. The capacitors also don’t care if they stay in storage for a long time. The only real downside is they don’t have the capacity that batteries can have, but for a small computer like a Pi Zero it is pretty easy to gang up enough capacitors to do the job.

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Linux Fu: Monitor Disks

November 5, 2020 by Al Williams 7 Comments

If you want a quick view of a Linux system’s process load, you can use top or — slightly nicer — htop. But what if you want a quick snapshot of how the disk system is doing? There are a few tools you can use, some of which are not nearly as common as top.

First, iotop

Most similar to top is iotop. This program shows you the total and current disk read and write numbers for the file system and also shows you who is eating up the most disk I/O. This screen looks busy:

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Rebuilding A Hero (the Robot, Not The Sandwich)

November 5, 2020 by Al Williams 27 Comments

When [Scott Baker] found a Heathkit Hero Junior on eBay, he grabbed it. He had one as a kid, but it was long sold. The robot arrived with no electronics, so the first order of business is to give it some new modern brains including an ATMega328 and a Raspberry Pi. You can see the start of the project in the video below.

So far, you can see a nice teardown of the chassis and what’s left of the little robot’s drive system. This wasn’t the big Hero-1 that you probably remember, but it was still a pretty solid platform, especially for the time it was on the market.

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Make Some Noise Or Simulate It, At Least

November 3, 2020 by Al Williams 6 Comments

Noise is a fact of life, especially in electronic circuits. But on our paper schematics and just as often our simulations, there is no noise. If you are blinking an LED on a breadboard, you probably don’t care. But if you are working on something meatier, handling electrical noise gracefully is important and simulation can help you. [Ignacio de Mendizábal] has a great piece on simulating EMC filters using LTSpice that can get you started.

There are many ways of classifying noise and [Ignacio] starts with common-mode versus differential noise, where common-mode is noise with current flowing in the same direction without regard to the circuit’s normal operation, and differential noise having currents that flow in the opposite direction of normal current flow.

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TTL Simulator In JavaScript

November 2, 2020 by Al Williams 13 Comments

How do you celebrate your YouTube channel passing the 7400 subscriber mark? If you are [Low Level JavaScript], the answer is obvious: You create a 7400 TTL logic simulator in JavaScript. The gate simulations progress from simple gates up to flipflops and registers. You could probably build a 7400-based computer virtually with this code.

In addition to just being fun and interesting, there were a lot of links of interest in the video (see below) and its comments. For one, someone watching the channel took the code and made a Verilog-like IDE that is impressive.

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OpenOffice Or LibreOffice? A Star Is Torn

November 2, 2020 by Al Williams 105 Comments

When it comes to open source office suites, most people choose OpenOffice or LibreOffice, and they both look suspiciously similar. That isn’t surprising since they both started with exactly the same code base. However, the LibreOffice team recently penned an open letter to the Apache project — the current keepers of OpenOffice — asking them to redirect new users to the LibreOffice project. Their logic is that OpenOffice has huge name recognition, but hasn’t had a new major release in several years. LibreOffice, on the other hand, is a very active project. We could argue that case either way, but we won’t. But it did get us thinking about how things got here.

It all started when German Marco Börries wrote StarWriter in 1985 for the Zilog Z80. By 1986, he created a company, Star Division, porting the word processor to platforms like CP/M and MSDOS. Eventually, the company added other office suite programs and with support for DOS, OS/2, and Windows, the suite became known as StarOffice.

The program was far less expensive than most competitors, costing about $70, yet in 1999 that price point prompted Sun Microsystems to buy StarOffice. We don’t mean they bought a copy or a license, they bought the entire thing for just under $74 million. The story was that it was still cheaper than buying a license for each Sun employee, particularly since most had both a Windows machine and a Unix machine which still required some capability.

Sun in Charge

Sun provided StarOffice 5.2 in 2000 as a free download for personal use, which gave the software a lot of attention. It eventually released much of the code under an open source license producing OpenOffice. Sun contributed to the project and would periodically snapshot the code to market future versions of StarOffice.

This was the state of affairs for a while. StarOffice 6.0 corresponded to OpenOffice 1.0. In 2003, release 1.1 turned into StarOffice 7. A couple of years later, StarOffice 8/OpenOffice 2.0 appeared and by 2008, we had StarOffice 9 with OpenOffice 3.0 just before Oracle entered the picture.

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Kelvin Probes Review Shows How 4-Wire Resistance Measurement Works

October 31, 2020 by Al Williams 12 Comments

You might think the probes in the picture are just funny looking alligator clips. But if you watch [tomtektest’s] recent video, you’ll learn they are really Kelvin probes. Kelvin probes are a special type of probe for making accurate resistance measurements using four wires and, in fact, the probe’s jaws are electrically isolated from each other.

We liked [Tom’s] advice from his old instructor: you aren’t really ever measuring a resistance. You are measuring a voltage and a current. With a four-wire measurement, one pair of wires carries current to the device under test and the other pair of wires measure the voltage drop.

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