Originally published by Paul Stenning in Electronics and Beyond (The Maplin Magazine), November 1996

• Diagrams and Schematics

Introduction
Many household items are now supplied with remote control handsets - all designed to encourage laziness! However, to adjust the room lighting it is usually still necessary to get up and do it manually. This is probably because the lighting was specified by the house builder, and most householders are understandably reluctant to alter it. Some single channel remote control dimmers are becoming available, but they are still rather expensive.

The system described here allows up to four channels of lighting to be remotely controlled. It has been designed to be relatively inexpensive, without compromising safety and reliability.

Such a system could be helpful for persons who cannot move as easily as they would like, such as the elderly or disabled. If necessary in individual cases, the remote handset may be housed in a larger box with suitable push buttons.

The prototype was used as a stand-alone system, connected to table lamps and a desk fan. Ambitious constructors could consider incorporating the unit into the household wiring, if they are satisfied that the installation will comply with the relevant wiring regulations.

System Overview
The receiver consists of a motherboard, onto which are mounted separate control modules for each channel. Two different types of control module are available. The first, and probably more popular type, is the dimmer module. This allows up to 400W of lighting to be switched or dimmed from a single button on the remote handset. This module can only be used with resistive loads such as normal incandescent light bulbs. It cannot be used with inductive loads such as fluorescent lights, low voltage transformer powered lighting etc.

For inductive loads the switch module may be used. This allows switching only, and can be used with any type of load up to 600W. As well as lighting (including fluorescent and transformer powered), it could also be used to control other loads such as fans, low power heaters and video game consoles.

This module can be configured to either of two modes of operation by means of a single link. Probably the most useful is Toggle, whereby the load is switched alternately on and off each time the remote button is operated.

In Momentary mode the load is only driven while the button is pressed. This may be useful for operating outdoor security lights, or for activating a bell or sounder to call for assistance.

Each of the four channels may also be operated by touch sensors on the receiver box - very useful if the handset gets lost or the battery is flat! The remote control handset is built into a proprietary case with built-in buttons and battery compartment.

Infra-red Communication Link
If I was designing this system two or three years ago, I would have specified the MV500, MV601, SL486 and SL490 ICs for the remote control system. However GEC-Plessey have now classified these useful devices as obsolete which means that, although supplies may still be available, they are not recommended for use in new designs.

To further complicate the situation, there appears to be no other devices available to carry out similar functions. This is probably because most equipment manufacturers use their own custom remote control ICs to ensure that their coding is different from every other manufacturer. Thus the demand for standard remote control ICs has declined.

In this design I am using the HT12E and HT12D devices from Holtek. These result in a design that is more complicated and gives slightly reduced range compared to that obtained with the GEC-Plessey devices. However I have very little choice - the Holtek devices are about the best of a fairly poor range of available ICs.

This should not be taken as a criticism of the devices themselves, since they are intended for security coding systems (such as car alarms and cordless telephones) rather than infra-red remote controls.