CHAPTER 15

Control Requirements

In this chapter, you will learn about

•  Modern types of control system and the devices they can control

•  Control system configurations

•  Control system design and performance verification

Control systems allow people to operate complex AV equipment using simple interfaces. Usually, these interfaces are located in a single convenient location within a room, such as at a lectern or on a wall near a door. Today’s users also expect a control system to meet their needs regardless of the interface type.

The best control system designs fulfill users’ need to collaborate as well as to control their environments in a familiar and seamless way. When all aspects of a system have been designed correctly, the AV system becomes a powerful business tool for anyone to use.

Because AV systems have become highly contextualized, control systems are the “glue” that holds systems together. They make it possible for AV professionals to create systems out of diverse components from different manufacturers.

Types of Control Systems

What types of devices can users control today? From AV equipment to environmental/energy components and security/access control—the number of devices that can be controlled from a central point keeps growing.

What types of control systems can users employ today? The following are just a few:

•  Traditional control system processor (i.e., relays, RS-232, input/output [I/O], and infrared [IR])    While reliable, this type can also be expensive and require firmware updates and extensive manufacturer training for propriety control software. Examples include Crestron Pro2 Dual Bus and AMX NetLinx Integrated Controller.

•  Control built in to the system (i.e., performs actions without a secondary interface, and the same manufacturer that provides the system provides the user interface)    While less expensive than traditional systems, this type is proprietary and less flexible. Examples include CyViz Display Controller and Cisco EX90.

•  Computer-driven control (i.e., provided and programmed by the end user)    While highly accessible through the Web and driven by bring your own device (BYOD)/standard mobile devices, this type is dependent on operating system updates and versions and may not be scalable. One example is Opto 22.

•  Cloud-based control    While capable of controlling large and multiple environments and providing robust backup, failure can be expensive. Examples include Jydo Controls and Surgex Axess Manager.

•  Habitual-learning systems    While capable of learning user patterns, this type’s data processing has not been perfected and may be expensive. Examples include Nest products and adaptive control systems.

Control System Components

The complete control system consists of a central processing unit (CPU), programming, external controls, connected devices, interfaces, software, control points, and the wiring. The following sections will discuss the basic subset of those components—the CPU, interfaces, and control points.

Central Processing Unit

A central processing unit or master control unit is the “brains” of the control system, typically consisting of a computer processor that communicates with a fixed set of devices on a local area network (LAN). The CPU is rated similarly to a computer system—based on the control protocols, control signal speed, random access and read-only memory (RAM and ROM), number and variety of bus devices, and so on. CPU capabilities determine how many keypads, push buttons, touch panels, dimmers, media players, computers, and other elements are possible within the system. Individual control systems can also be linked together to form larger, composite control systems.

A CPU can be used to control multiple zones and devices by performing a series of automatic and independent functions. The CPU requires an operating system that allows a custom or fixed program to run the processing operations. The program defines the choices, variables, calculations, and fixed functions for the processor to choose from.

Processors are a central component of a control system. Some control systems have a single master controller, while others have several. CPU-to-CPU or master-to-master systems refer to systems that enable data processing in more than one location simultaneously, for a combined effect. Small self-contained systems can be linked together to provide better reliability, redundancy, independence, and efficiency. CPU systems provide hierarchy control, with one leader (in other words, master controller) and many subcontrollers (in other words, devices). Automated systems without user interfaces use an input interface to the CPU, which in turn communicates to the input interface.

The master unit (Figure 15-1) provides an example of the range of device interfaces that may be available within a control system. In this case, the master controller provides connections supporting a wide range of devices, including legacy devices.

Figure 15-1    The CPU master unit

Control Interfaces

A control interface is a graphical and functional method of device control that uses programmable command sequences. For example, let’s assume a user would like to turn on a light by pressing a button on a touch panel. This command is sent to the CPU, which sends the signal out across a wire/cable using the correct control point. A contact closure (in other words, the control point) activates the switch, and the light turns on.

Control interfaces can be wired or wireless. Complex wired control systems can be control rooms that operate nuclear plants and systems to control lighting and other elements of live theatrical shows. New technology merges the wired control with wireless computers that utilize graphical user interfaces, feedback displays, and push buttons.

What type of interface might your users need for their control environment? Control interfaces have different aspects that you’ll need to communicate to your client so you can both decide on the best device for the space.

•  The touch-screen panels (in other words, touch panels) are the most popular style of control (Figure 15-2). They are inexpensive, hard to lose, and easy to operate. The touch screen offers the most flexibility and style and can be wired or wireless.

Figure 15-2    A touch-screen control panel

•  Control panels incorporate push buttons, knobs, and sliders. They are the predecessor of touch-screen panels and can still be found and selected for use in professional AV environments.

•  Simple wired panels are the most common user interfaces. Simple wired interfaces are used to control devices within a typical home and can include wall switches and doorbells. In professional AV environments, they provide media player access and control.

•  Handheld remotes and app-enhanced mobile devices may also be used in conjunction with other types of control interfaces. Handheld remotes don’t typically include programmable control or graphical user interfaces (GUIs). Traditional handheld remotes are preprogrammed and have only pushbuttons, such as the remote that comes with a TV or Blu-ray Disc player. Some newer universal remotes have GUIs, while both old and new universal remotes incorporate programmable control. Many also have macro capabilities—one button turns on the TV and Blu-ray Disc player, switches the TV to Blu-ray Disc input, and so on.

AV professionals create an intuitive design to ensure the interface is easy for the user to understand and that it is installed in appropriate locations within the room, ensuring easy access within the environment (for example, out of direct sunlight that can affect visibility).

Smartphones and tablets have changed the way people interact with technology. Furthermore, these devices have changed user expectations. Users have been conditioned to expect discoverability and understanding.

Discoverability allows a user to determine which actions are possible and where or how they can perform them using a device. Understanding gives users a clear sense of how a product or device is supposed to be used. These characteristics are the key elements of human-centered design.

Human-Centered Interface Design

Human-centered design considers user behaviors, capabilities, and needs before technology and creativity. According to this approach, the design process begins without specifics and focuses on what the user might look for when interacting with devices. The resulting design informs the user if an action is possible, displays the action as it occurs, and notifies the user if something goes wrong.

The following are some of the characteristics of human-centered design:

•  Affordance    Build intuitive interactions between people and their environment (for example, mail slots fit only envelopes, and balls allow for throwing or bouncing).

•  Signifiers    Signal what actions are possible and how they should be done (for example, door knobs or handles can signal turning, pushing, or pulling).

•  Constraints    Communicate what the design can or cannot do (for example, push versus pull on a door).

•  Mapping    Lay out the design for clear understanding (for example, turn wheel left to turn left).

•  Feedback    Communicate the results of an action. The feedback must be immediate, informative, and specific (for example, elevator up/down buttons).

Users could get frustrated if they can’t figure out how to use the control system to make the lights dim or how to make the screen come down to project their presentations. If users can’t figure out the controls, they’ll be discouraged from using the interface. A human-centered interface allows the user to utilize a control system without any technical knowledge.

For example, users expect some form of feedback confirming a selection they have made in a given space. After pressing a button on a touch panel, they expect to see the drapes lowered, the projector lowered and powered on, and the button they pressed turn green. The actual devices in this scenario do not require two-way communication with the user, but users may still expect some form of positive feedback from the interface.

Consider a few of the elements when designing the user interfaces. You and your client should determine how easily the user can do the following:

•  Determine what the system is for

•  Figure out which device options are possible

•  Identify and interpret the system state and if it is a desired state

•  Figure out which buttons to press or knobs to turn in the shortest sequence possible

Control Points

A control point (Figure 15-3) is the vehicle that connects devices to the control system CPU. For example, a touch panel would be a control interface, and the control point could be RS-232 or Ethernet. When the user touches a button on the touch panel, the control point communicates the information from the CPU to the device.

Figure 15-3    A control point

The control point types range from basic (contact closure) to advanced (Internet Protocol) in complexity.

•  Contact closure    The simplest form of remote control by opening/closing a circuit.

•  Analog voltage (in other words, voltage ramp generator)    The analog form of data control. The voltage of a specific parameter is applied to the control point to adjust the level by a specific ratio of voltage value to the device’s level.

•  Serial communication    A one-way communication available in optical and wired formats. It most commonly uses infrared, which is a pattern of light pulses emitted from a light-emitting diode that is in turn recognized by the device’s control point. Transmission requires a direct line of sight. Not all serial communication uses IR. Serial communication is also capable of bi-direction, just not in the IR form. IR is one way, unless there are two separate IR channels (IR transmitting [Tx] and IR receiving [Rx]).

•  Radio frequency (RF)    Can be bi-directional and is mostly used by the user interface to the control system. Transmission has to be tested to prevent interference issues.

•  Network    Works on the basis of transmitting packets of digital information (control protocols). The three forms of such transmission are as follows:

•  Single ended    Bi-directional between two devices.

•  Broadcast    A single transmitter of information and multiple receivers. All receivers “hear” the broadcast but respond only to traffic directed to itself.

•  Multidrop    Multiple transmitters and multiple receivers all interacting on the same wire/cable. This subtype can be complex and requires careful setup. Its formats are RS-232 and RS-422. RS-232 connects a single device back to a processor. RS-422 is a balanced connection and provides increased distance capacity via differential signaling. Differential signaling can transmit data at rates of up to 10 megabits per second or may be sent via cables up to 4921 ft (1500 m) long.

•  Internet Protocol (IP)    Similar to network but allows for communication between the Internet, control components, applications, and so on.

•  Ethernet    Considered a stand-alone type because of the incredible flexibility and applications it provides, although it really is a data control type (in other words, IP). It can be used to address enterprise-wide support issues and link global resources together.

The following sections explain the control system design and performance verification.

Control System Design

For AV control systems, the information gathered from the user during the needs analysis should be applied to every step of the design process. AV professionals must determine exactly what kinds of functionality and features the users need. Such an approach helps to avoid and solve many problems early on.

Needs Analysis

These are some general concepts to ask or listen for when interviewing the client:

•  Simplicity of operation    Who are the users of the system? What is the user’s level of technical experience?

•  Device automation    What do they want the system to do autonomously?

•  Multiple device integration    How many devices do they want to control?

•  Device operation from multiple locations    Where should interfaces be located?

•  Device operation at a distance    How do they want to control devices? Consider any pre-existing systems or future expansion issues.

•  Cost    What is the project budget?

For each device to be controlled by AV professionals, choose an appropriate control interface by considering the following issues:

•  Can the CPU accommodate all of the system’s needs?

•  What control interfaces are available and required for this device?

•  How does the selection impact other subsystems?

CPU Configurations

Devices may need to be controlled in multiple rooms, across a college campus, or even in another part of the world. In these advanced configurations, multiple interconnected CPUs may be required. These configurations are often referred to as centralized, client-server, and distributed. Control system professionals use these terms for one or many processes.

A centralized system consists of a single CPU and many devices and is the most common configuration in the field.

Figure 15-4 shows a configuration known as client-server. If the control or server CPU fails, the client CPU also fails because it cannot receive instructions from the primary CPU. The client CPU can act like a pass-through. In other words, the client CPU is receiving control from the actions of the GUI connected to the control CPU. In Figure 15-4, the client has no associated control surface or GUI (touch panel, button pad, UI), so it relays only the commands from the control CPU.

Figure 15-4    Client-server configuration

The configuration shown in Figure 15-5 is known as distributed processing. It has multiple independent systems linked together by a data network. If the network link fails, each system can still function independently, but the tasks between the systems are lost.

Figure 15-5    Distributed processing

Programming for Control

After they understand which devices the client needs to control, AV professionals draw or write out how these devices can be controlled with control points. This step includes transferring the list of devices and device actions to a control functions script.

A control functions script is an itemized list of devices to be controlled that helps to organize what needs to be done by everyone on the project, such as the client, programmers, designers, and facility engineers. It contains the required actions for each device and interconnection information, such as the control point and connector type. Some of the items on the list may not be AV related (for example, drapes, lights, and temperature sensors).

A control functions script also assists the designer in creating a control system that meets the required client needs. AV professionals discuss the control functions script and sketches with the client to receive their approval of the overall system functionality.

Establishing Control Points

In some cases, the design is complex and requires a careful selection of control points, such as in a system that consists of a large number of conference microphones, simultaneous interpretation systems, or voting systems. Regardless of the project complexity, AV professionals should refer to the approved control functions script and choose control points that most efficiently meet the design need.

Once the control points are selected, the control function script should be updated to reflect the choice. The next step in the process is to verify that the design can be implemented.

Verifying System Performance

During the system’s performance verification, AV professionals ensure that devices can be controlled correctly and that the system matches up with the client’s narrative. It is important to stay informed about product changes. For example, a user might not be able to control a device using a previous version of a control point three months after the implementation.

Communicate the verification results to the client, even if the system passes the verification test. Refer to ANSI/INFOCOMM 10:2013, Audiovisual Systems Performance and Verification, and the related guide for more information on how you can test your system’s performance.

Finally, start formally designing your control systems around what you’ve discovered from the previous steps. This way, the problems will be taken care of and you won’t have to re-design the system.

Chapter Review

In this chapter, you learned that the success of a control systems project largely depends on the choices you as an AV professional make. If your control system focuses on human behavior first and technology second, then users will be even more empowered to take advantage of all they have to offer.

You also learned that when designing a control system, things can get pretty complex. It’s especially important to establish a good rapport with clients and the users and communicate the project progress and changes on a regular basis. The next chapter will cover network design for AV systems, which you will also find useful for control system design.

Review Questions

The following questions are based on the content covered in this chapter and are intended to help reinforce the knowledge you have assimilated. These questions are not extracted from the CTS-D exam nor are they necessarily CTS-D practice exam questions. For an official CTS-D practice exam, download the Total Tester as described in Appendix D.

  1. Which of the following is a type of control system?

A. Computer-driven

B. Cloud-based

C. Habitual learning

D. All of the above

  2. Which of the following control system components is used to control multiple zones and devices by performing a series of automatic and independent functions?

A. Control interface

B. Control point

C. Central processing unit

D. Control system software

  3. What is the purpose of mapping in human-centered interface design?

A. Communicate the results of an action

B. Communicate what the design can or cannot do

C. Lay out the design for clear understanding

D. Signal what actions are possible and how they should be done

  4. Which CPU configuration has multiple independent systems linked together by a data network?

A. Client-server

B. Centralized

C. Scattered

D. Distributed

  5. What list helps to organize what needs to be done by everyone on the project?

A. System component list

B. Control functions script

C. Materials list

D. Control object list

Answers

  1. D. Control systems can be computer-driven, cloud-based, or habitual-learning systems.

  2. C. A central processing unit is the part of a control system used to control multiple zones and devices by performing a series of automatic and independent functions.

  3. C. The purpose of mapping during human-centered interface design is to lay out the design so it’s easier to understand.

  4. D. A distributed CPU configuration includes multiple independent systems linked together by a data network.

  5. B. A control functions script lists the devices to be controlled and helps organize what needs to be done by the client, programmers, designers, and facility engineers.