This is in contrast to a conventional energy monitoring and. The need for linear response in modulating control loops has not been eliminated by the introduc tion of digital controls. Control terms before discussing the various control actions, here is a short list of terms and abbreviations used in this section. The analogue output is to control the field actuators devices. The ddc or direct digital control takes that to a much higher level by enabling the automated central control of. The ddc controller receives the inputthe ddc controller receives the input from the sensor, performs a logic function and processes an outputfunction, and processes an output. Show the correct action with arrows at each component h d f li dt when used for cooling mode. The microprocessor in ddc, the inputs and outputs in the form of inputoutput io modules send information to and from a microprocessor to control the operation of hvac system equipment. The microprocessor could be programmed to adjust an air handler mixed air damper based on the relative. Pdf direct digital control for building hvac systems pp 116 cite as. To accomplish this goal, a generic framework of the various components and configurations used in current ddc systems has been defined. Automatic and ddc control fundamentals and energy conservation for hvac equipmentpart 1 11. Specifying a direct digital control ddc system contemporary. Introduction to direct digital control, ddc as briefly mentioned earlier, small computer processors operate direct digital controls, ddc.
The control is accomplished by digital electronics that read or. Direct digital controller installation, use and programming. The meanings and uses of the terms will become clear as we progress through the next couple sections. Direct digital control ddc is a control process in which a microprocessor controller constantly updates an internal information database by monitoring information from a controlled environment and continuously produces corrective output commands in response to changing control conditions. This process is similar to the way traditional control systems work, except that digital information processing produces a much faster and more accurate control system response under all conditions at all. The analogue inputs is to monitors the fields sensors values. All instrumentation is gathered by various analog and digital converters which use the network to. Direct digital control ddc systems instrumentation tools. Digital means that they operate on a series of pulses, as does the typical pc computer. Direct digital control ddcis a control process in which a microprocessor controller. Computer control has been introduced to many things over the. The purpose of this guide is to describe, in generic terms, the various architectures, hardware components and software associated with direct digital control ddc systems. This change is the introduction of direct digital control ddc to hvac systems.
Introduction to direct digital control systems springerlink. Pdf specifying a direct digital control ddc system. Integrated digital controls have long been an industry standard in hvac equipment. All instrumentation is gathered by various analog and digital converters which use the network to transport these signals to the central controller. A loop is a sequence of instructions, which are executed until a condition is satisfied. Ddc or direct digital controller usually has the followings features. Direct digital control takes a centralized networkoriented approach.
Direct digital control ddc open systems a consumers guide to. Chapter 1 introduction to direct digital control systems purpose of this guide. According to levenhagen and spethmann, direct digital control is the use of computers or microprocessors in conjunction with sensors and actuators to provide closedloop control. When designing your hvac system with digital control. Over the last sixty years, control systems have evolved from. Exercisethe control drawing below has a direct acting controller, with a no valve. In the ddc system, all the inputs and outputs remain, however, they are not processed in the controllers, but are carried. Direct digital control is the automated control of a condition or process by a digital device computer. This process is similar to the way traditional control systems work, except that digital. Direct digital control ddc is the automated control of a condition or process by a digital device. Computer control has been introduced to many things over the past few years, from automobile engines to home appliances to most industrial processes, but only recently have small computer control systems been introduced into the space conditioning industry. Direct digital control system ddc is a term frequently found in building automation specifications.