Now that all the PC boards have been built, it's time to prepare the metalwork. Hopefully, this unit will be made available as a complete kit, in which case the metalwork will be supplied pre-drilled.

Alternatively, if you're buying the bits separately, you will have to drill the case yourself.

As supplied, the case comes in pieces and it's a good idea to drill the front and rear panels before putting it together. The front and rear panel artworks (Fig.12) and the main wiring diagram (Fig.10) show the positions of these holes.

Starting with the front panel, you have to drill holes for mains switch S1, the 20-LED display, the three pushbutton switches, the acknowledge LED and the infrared receiver. The rectangular cutouts for the mains switch and LED bargraph can be made by first drilling a series of small holes around the inside perimeter of the cutout, then knocking out the centre piece and filing to the correct shape.

Don't make cutout for the mains switch too big - it must be a tight fit so that it is properly secured by its retaining tabs. The pushbutton switch holes should be about 9mm to allow clearance for the 7.5mm diameter switch caps.