Day: July 12, 2023

You’ve Got Mail: Sorting And The USPS

July 12, 2023 by 52 Comments

Snail mail. You may not think much of it these days, but the mail doesn’t stop and it never has. Every type of mail from postcards and letters to large envelopes and packages of all sizes moves every single day all over the US, even though it isn’t typically delivered on Sundays. Dealing with the ever-increasing volume of physical mail has called for the invention and evolution of automatic mail sorting machines that are used by both postal facilities and businesses alike.

While mail sorting machines have grown and matured over the years, the human element of the task remains intact. As long as people type addresses, write them by hand, and/or print them in handwriting fonts by the hundreds, there will need to be humans on hand to verify at least a few of them that are really hard to read.

There are roughly a dozen different types of mail sorting machines in 2023. In this series, we’re going to take a look at most of them, along with many other aspects of the United States Postal Service and its history.

Continue reading “You’ve Got Mail: Sorting And The USPS” →

SuSE Take On Red Hat, Forking RHEL

July 12, 2023 by 18 Comments

One of the Linux stories of the moment has come from Red Hat, with their ongoing efforts to make accessing the source of their Red Hat Enterprise Linux product a paid-for only process. This has caused consternation and annoyance alike, from the open source community angry at any liberties taken with the GPL, and from the community of RHEL users and customers concerned as to what it might mean for them.

Now a new player has entered the fray in the form of SuSe, who have announced the creation of an RHEL fork with the intention of maintaining a freely-available Red Hat compatible operating system distribution.

This is good news for all who use Red Hat derived software and we expect the likes of Rocky Linux will be taking a close look at it, but it’s also a canny move from the European company as they no doubt hope to tempt away some of those commercial Red Hat customers with a promise of stability and their existing experience supporting Red Hat users through their mixed Linux support packages. We hope they’ll continue to maintain their relationship with the open source world, and that the prospect of their actions unleashing a new commercial challenge causes Red Hat to move away from the brink a little.

Need some of the backstory? We’ve got you covered.

The perfect header for this story comes via atzerok, CC BY-SA 2.0.

Proper Decoupling Capacitors

July 12, 2023 by 37 Comments

If you’ve been building circuits for any length of time, you probably know you need decoupling capacitors to keep your circuits stable. But even though it’s a favorite technique of ours, just scattering some around your PCB and hoping for the best isn’t necessarily the best approach. If you want to dig deeper into the why and how of decoupling, check out [Stephen Fleeman’s] post on the topic.

It is easy to think of capacitors as open circuits at DC and short circuits at high frequencies, shunting noise to ground. But the truth is more complex than that. Stray resistance and inductance mean that your simple decoupling capacitor will have a resonant frequency. This limits the high frequency protection so you often see multiple values used in parallel to respond to different frequencies.

Because the stray resistance and inductance plays a part, you may want to use fatter traces — less resistance — and shorter runs for less inductance. Of course, you can also use power and ground planes on the PCB as a form of decoupling. At the end of the post, [Stephen] talks a little about the importance of digital and analog ground that interact in a specific way.

If you want to do some empirical testing, you can build a test rig and do the work. Or check with [Bil Herd] about PCB inductance.