Monash University

School of Computer Science and Software Engineering

"Smart House" Workshop.


What is a smart house?

Imagine you have a house fitted with a variety of sensors and electronically operated devices. For example,


Each of these sensors is wired to a computer, which can monitor the values and perform various actions. Possible actions might include:


These are all possible actions for a "smart house", one which is controlled by a central computer.


How do I build a smart house?

A naive solution to this problem is shown in Figure 1. Each sensor is wired back to the central computer using a separate cable. An interface at the computer allows a program to probe the values being returned by each of the sensors, and makes it possible to control the various alarms and output devices. However, the problem with this approach is that the system requires many wires, all originating with the host computer. Such a solution would be cumbersome and expensive.


Another alternative it to use a shared network, which winds its way throughout the various rooms of the house, as shown in Figure 2. In this scheme, each sensor is connected to the network, and it only responds when prompted by the host computer. Unlike the centralised scheme, only one long wire (or bus) is required to communicate with all of the sensors and output devices. In this case, each sensor needs to be intelligent enough to send its value down the network wire – we have called these "smart nodes".

Figure 1 – A naive implementation of the smart house


Figure 2 – A bused solution to the smart house

What does a "smart node" do?

Each device on the bus must be able to collect the external signals and communicate these back to the host computer. It must also be able to take output directives from the host and send these to the various devices which need to be controlled.

We have decided to build each of these nodes using a number of special purpose digital integrated circuits, and these are assembled onto a circuit board. Each "smart node" board can take a variety of analogue signals, from up to 4 devices, and can combine them into special communications "packets" for transmission back to the host computer. Also, each node board can distribute up to 4 analogue signals to external devices. The bus is connected to the node board, and simply passes from one board to another until the house is completely wired.

What sort of devices does the node support?

The current "smart node" can be connected to a variety of input devices. We have developed circuits which allow the system to:

Circuits have also been developed to allow the outputs of the node to drive:

You will be provided with these circuits in the workshop, together with a prototyping board for building some of them.

What does the host computer do?

The host computer runs a special control program, which samples the values for each of the external devices. In the basic software which is provided, the program allows you to select a device, and it will report the status of the device. The software also allows you to control a number of simple devices by turning them "off’ or "on". The program is written in visual basic.

The host is connected to the "smart nodes" by the serial RS232 communications port of the PC.


Basic Components

The kit you have been supplied includes:

All of the necessary components and tools will be available during the workshop, including soldering irons, multi-meters and hand tools.

The workshop

The workshop timetable will be organised as follows:


9:00 AM

9:30 AM

Introduction and discussion of project

9:30 AM

11:00 AM

Construction of "smartnode" board and interface electronics

11:00 AM

11:30 AM

Coffee break

11:30 AM

12:00 PM

Testing and Calibration

12:00 PM

1:00 PM



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