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Final Assembly
The prototype was assembled in a plastic case 165mm x 67mm x 190mm, and was not fitted with touch sensors.

The outputs were bought to four IEC sockets fitted onto the rear panel. The live and neutral to these sockets are connected to the terminals on the motherboard, and the earths are connected directly to the incoming earth. The wiring diagram is shown in figure 9. Any exposed metal parts (apart from the touch sensors) must be securely connected to earth.

The mains input cable and the connections to the sockets must be made with 6A (0.75 sq mm) wire. The unit should be fitted with a 13A plug, fitted with a fuse not exceeding 5A. If the unit is being used to control small loads such as table lamps the plug fuse should be reduced to a more suitable value, such as 3A.

The PCB is mounted in the case using insulated stand-offs. For safety reasons do not use metal spacers to mount the PCB. A suitable cutout should be made in the front panel to allow the IR to reach the sensor. This opening must be covered with a piece of red filter material, glued securely to the inside of the case. Remember that the screening can is at mains live potential.

If touch sensors are used they should be mounted on the case so that the mounting screw penetrating into the case does not come close to the PCB assembly or any live terminals. Solder tags should be positioned under the mounting screws, and connected to the PCB with insulated flexible wire. Ensure the soldered joints are secure, as a hazardous situation could occur if a wire should come adrift and make contact with a live terminal.

Another option might be to use push switches in place of the touch sensors (this would allow a metal case or panel to be used). These switches must be rated for use at mains voltages, even though the current is minimal. One side of the switch is connected to the touch sensor terminal, and the other side is connected to neutral.

Installation and Use
The loads to be controlled should be fitted with IEC plugs, and connected to the appropriate sockets on the back of the unit. If any cables need to be extended, use proper enclosed connectors - not choc-block or insulation tape!

The unit should be positioned so that the remote control can be pointed towards it from the usual sitting position. If touch sensors have been used the unit will need to be accessible.

Remember that this unit does not provide isolation from the mains. Even when a channel is switched off there may be sufficient current passing through the filter capacitors to give an electrical shock. Always disconnect the unit from the mains before altering the connections or replacing light bulbs.

Alternative Arrangements
Some constructors may wish to incorporate the unit into the household wiring. Before carrying out such an installation, it is essential to determine whether this will contravene the relevant wiring regulations and any local planning and fire regulations. Remember that such contravention may affect your home insurance and any building warranties. Advise on such matters is beyond the scope of this article.

The wiring arrangements would be similar to that shown in figure 7, although there would obviously be no IEC sockets. It will probably be necessary to provide a separate mains isolator for the unit, for safety when replacing light bulbs.

The neutral connection to the lights will probably take a different route in the household wiring, in which case only the live connection to the lights should be connected to the unit. It is still necessary to bring a single neutral connection to the unit to power the electronics.

The unit itself does not require an earth connection, but any exposed metal parts (apart from the touch sensors) must be properly earthed.