What is PVID

PVID is short for Port VLAN identifier. The PVID of a port is the VLAN id that will be assigned to any untagged frames entering the switch on that port (assuming the switch is using port-based VLAN classification). This is a concept that is defined in IEEE 802.1Q. For example, if you intend to connect… Read More »

Textual Ladder Logic Notation with Unicode Box-Drawing Characters

I recently completed a simple PLC project and wanted a way to document the ladder program only using text. Here’s what I came up with for a simple PLC where each program element can be represented with 3 characters: ┌001─002─003─004─005─006┐ ┌NOTES───────────────────────────────────────────┐ 001├─I1─────────────────∫Q1┤ │Button pushes at I1 toggles light at Q1 │ 002├─I2─────────────────∫Q2┤ │Button pushes at… Read More »

Play Minecraft with One Hand

Note: Links to Amazon.com are affiliate links which means I will get a small commission from Amazon (at no additional cost to you) if you buy something after following my link. I recently broke my finger and had limited use of my left hand for several weeks. Priority one in in this type of situation… Read More »

Install VirtualBox guest additions on CentOS 7

I am starting with CentOS 7 minimal install, but the steps should work wherever you are starting. In The Host OS First you need to find the Virtual box guest additions iso.  It’s harder to find than it should be. In the host OS (not in the CentOS VM) go to download.virtualbox.org/virtualbox and navigate to your… Read More »

Why you need HTTPS for your web site

The TL;DR: You should not run a website that requires a login without enabling HTTPS on that web site and forcing the use of HTTPS for, at the very least, the login and administration pages. Logging in without HTTPS may allow somebody to steal your password and hack your web site. You should arrange to get… Read More »