In part 1 and part 2 of this series on RS-485 we covered the basics. Let’s take some of that knowledge and talk about what most often goes wrong with RS-485. I want to give you the ability to red flag common mistakes and some knowledge that will help repair the most common issues. I am going to take some of the knowledge we gained from the last two posts and put it into context for both existing RS-485 installations and new ones. I’ll discuss this in the form of red flags that will trigger the discussion.
In Part One One of this series of posts on RS-485, I gave a high level introduction to the structural and electrical components of RS-485 networks. This week I’ll elaborate on those concepts and delve a little more deeply into some of the industry terminology and how it applies to those concepts. As always, please feel free to drop a comment if you have any questions or want further discussion on any of this information.
What is RS-485 and what does it have to do with buildings or building controls? If you’re asking this question either you’re just curious, or maybe something isn’t working quite right and you’re Googling to find an answer. Either way, I plan on giving you a high level understanding of RS-485 in this post, and how having a better grip on how it works can help building operators and controls contractors control their building more effectively.
If you’ve worked in the Building Automation Systems (BAS) industry, you’ve probably heard of LonWorks, BACnet, and Modbus. These three open system networking technologies have been the foundation of most building automation systems over the last decade. They allow devices from different manufacturers to communicate data without issue (most of the time) so that a building’s chiller, boiler, and pumps may all work together as one system to give a building owner an integrated system that enables a high level of functionality.
I love simple concepts formulated using basic math. And even though I love all mathematics, I’ll be the first to admit that my math skills could always be stronger, so I am always trying to learn. I guess that’s why the basic formulas for really complicated concepts really resonate with my inner nerd. The Drake equation as a model for explaining the Fermi paradox is a wonderful example of these. Recently Bill Gates released a short speculation on YouTube regarding energy and CO2. This too really resonated with me as it’s an area where I see our industry really affecting change.
My whole life I’ve been a computer geek. Ever since I got my first TI-99/4 I started realizing that computers were a blank canvas of technology that I couldn’t resist drawing on. This passion carried me into Information Systems for my degree in college. In college I received an internship at a local Building Automation Systems (BAS) contractor programming HVAC systems. Through that internship I learned the value of using networked computer systems to generate actionable information, and how to automate a decision process from that information.
A friend of mine recently sent me an article from the Automatedbuildings.com online magazine entitled “Death of the Controls Industry” written by Therese Sullivan (Principal of Building Context Ltd). The article contains summary of a presentation given by Darren Wright, Director at Arup. Darren Wright makes the case that we have a major problem in the building energy market, and it’s directly attributable to the controls business model still not being open source.
When you’re asked to review someone else’s building automation system (BAS) programming, it’s a bit of a daunting task. This is because those of us who program building systems (or really any computer-driven system) for a living figure out that there are a million different ways to capture the same process in any given programming language. Usually no two people will do it the same way.
Topics: Building Cx & Design Review
Recently there has been a lot of talk resurfacing about what defines an "open system." It is a concept that has been debated and sold for well over a decade in the HVAC automation industry. There still seems to be some ambiguity about what this really means.
Topics: Standards and Metrics
I’ve noticed a common problem across a range of buildings due to the idea that all PID controls behave the same. The result of this misconception rears its ugly head in poor tuning and poor implementation of PIDs that can cause your HVAC system to perform poorly for years. The PID is a great means to realize your design intent, if you know how to properly spell out for your controls contractor what it is you’re looking for. But before that, let’s get the basics down first - What is a PID?