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Feedback

Simple home automation systems usually only provide one-way communication between controllers and the controlled devices. More sophisticated systems can also utilize two-way communications. This introduces the concept of feedback.

Feedback is data that is returned to a controller or program from a sensor or a controlled device. It can consist of either state or value information. For example, feedback might show:

Some systems can provide feedback directly to the user. For example, you could push a few buttons to check the current inside and outside temperatures, note the date and time, see who may have called when you were out, find out what music is playing, check the swimming pool chlorine level, etc.

More advanced systems allow you to use feedback when programming your system. This gives you tremendous flexibility. For instance, it you only wanted to water your garden during the night, and only if the soil has become too dry, you could program a sprinkler circuit to automatically switch on when a soil moisture sensor indicates a moisture level below a certain value and when a light sensor indicates a light level below a certain value.

Communication in the Home Automation System

To create a true home automation system, we must expand equipment control beyond the individual item, local area, or closed-loop circuit level. To do this, a system core must be created that acts as a communication network, allowing transmission of commands and data between system components.

At the minimum, commands must be able to reach equipment throughout the home, no matter where that equipment is located. More advanced home automation systems provide two-way communication capabilities, allowing feedback to be sent from the controlled equipment back to the controlling device or program.

There are several schemes for system communication, each with their own merits and drawbacks. The best home automation systems use a system core that combines several connection types, depending on which is best suited for the equipment types and how they will be used. The most common system core types include:

If you are restricted to using standard home wiring as your system core, your options are certainly more limited, but there are still a number of useful functions that can be automated. By adding controller modules with special power line communication capabilities or by using wireless communications, you can still integrate various equipment items into a useful home automation system, with varying degrees of centralized control.

But first of all, what can you do without applying any of these options? What can you do with nothing but basic home wiring? Generally, equipment control and automation is limited to the control capabilities that were included with a controlled device or available as an option. For example, a TV or VCR can be controlled with a hand-held remote control, a microwave oven has built-in programming capabilities, and a sprinkling system has its own programmable controller. You can also replace old "dumb" devices with "smart" devices. For example, a manually set thermostat can be replaced with a programmable thermostat, or a motion-sensing light switch can replace the old manually operated light switch. Some of these smart devices might come with wireless control accessories, although this generally only work with that device or some related equipment item.

The principal limitation with standard home wiring is that without additional communication capabilities, device control is restricted to individual devices, the effective radius of a remote control, or the closed-loop circuit level. For instance, you can use a hand-held remote control to operate or program a VCR, but it only works if the VCR is close enough to receive an infrared signal from the remote control; you can't use the remote control to operate a VCR in another room or a different floor. Similarly, only devices on a particular closed-loop circuit can be affected by a switch, dimmer, etc. installed on that circuit. For example, a dimmer switch can only control the light fixtures that are part of the closed-loop circuit in which the dimmer is installed, and it affects all of the devices on that circuit equally and simultaneously.

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