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Module PCB Construction
Up to four module boards are needed, and they may be any mix of dimmer and switch types. The dimmer module PCB layout and artwork are shown in figures 7A and 7B, while the switch module PCB is shown in figures 8A and 8B.

Construction is mainly straight-forward, but the following points should be noted. The triacs (T201 and T301) are laid flat against the PCB (metal tab towards the board), and are held in place with M3 x 6mm panhead screws and nuts. The fuseholders may be fitted with covers if required, but these will make it more difficult to change the fuses. C203 and C302 must be Class X or X2 rated components.

On the switch module a link must be fitted either between LK302 and LK303 (toggle mode) or between LK301 and LK302 (momentary mode). The module will not operate if no link is fitted.

On the dimmer module, join LK203 to LK202 on the PCB for mode A or join LK203 to LK201 for mode C. If mode B is required leave LK203 unconnected. The three different modes were discussed earlier.

The five pads along the lower edge of the PCB (J201-J205 on dimmer module and J301-J305 on switch module) are for connection to the motherboard. They should be fitted with single pins separated from a 0.1" SIL right angle header strip.

J206 and J306 are the connections for the optional touch plates. The PCB pads should be fitted with terminal pins if touch plates are to be used.

The switch module PCB has a number of fine tracks passing close to pads, so extra care should be taken to avoid inadvertent solder bridges. When construction is complete the boards should be cleaned with a suitable solvent.

Dimmer And Switch Module Testing
Note that each of the four module positions on the motherboard relates to a separate button on the handset. Module A is closest to the IR receiver, and is the left handset button.

The module boards are fitted to the motherboard simply by inserting the five pins through the relevant holes and soldering it in place. The modules will only fit one way round, and should be mounted at 90 degrees to the motherboard.

When a module board is fitted, connect a lamp to the appropriate pair of output terminals. The neutral terminal is the one closest to the mains input terminals. Connect the system to the mains and test the module using the remote control handset.

With the dimmer module, briefly pushing the button should turn the lamp on and off, while holding the button for a longer period will cause the brightness to vary up and down. When the button is released the lamp should remain at the brightness set.

With the switch module, the results depend on the link setting. In toggle mode the lamp should alternately turn on and off each time the button is pressed. In momentary mode the lamp should stay on only while the button is held.

The final test in each case is the touch sensor input. Set your test meter to the 2mA AC range and, with the mains off, connect it between J206 or J306 and earth. When you switch on the meter should read about 0.025mA (25uA). If it reads above 0.030mA (30uA) the cause must be investigated. To avoid the risk of accidentally touching live terminals, do not be tempted to touch the touch sensor inputs until they have been connected to suitable plates on the outside of an assembled enclosure.