WebEE

Construction
The circuit is constructed on a small single sided PCB. The whole circuit is connected to the mains, and a fault could result in an expensive mess. Therefore it is essential that you use good quality new components throughout. C1 and C4 must be Class X rated components, suitable for connection directly across the mains.

Take extra care when assembling the PCB, to ensure that all components are fitted correctly and all soldered joints are sound. All the wide PCB tracks carry significant current, and should be reinforced by adding solder along their whole length.

The LED positions should be fitted with terminal pins. Once the PCB is fitted behind the front panel, the LED leads can be soldered to the pins.

The PCB is designed to fit into a standard electrical double socket surface box. A double blanking plate is used as the front panel, and is drilled to suit the LEDs and PCB mounting screws. The PCB is mounted on 25mm long INSULATED spacers, with the components towards the panel. The internal photograph of the prototype should make this clear.

A front panel overlay is given in figure *. This may be photocopied and fixed to the panel with clear self adhesive vinyl sheet. Note that if this overlay is used the LED holes will not be directly above the LED positions on the PCB. Bend the LED leads to suit.

Screw the mounting box to a suitable piece of wood, with the master socket (single unswitched) to the left and the slave sockets to the right. Any number of slave sockets can be used to suit your requirements, bearing in mind the maximum total load rating of 1200VA. Before mounting the boxes, remove cable knockouts at the top of each end. Cable clips should be used to secure the incoming flex.

The interwiring is shown in figure *. Three core mains cable rated at 5A or greater should be used, and the earth wire is connected directly to the socket terminals. The socket terminals are intended for much larger cable, so the wire ends should be folded over twice and tinned first, to ensure a reliable connection.

The completed unit must not be permanently connected to the household wiring. It may only be connected by a length of flex and a 13A plug. Make sure the fuse in the plug is rated no higher than the flex being used, 5A will generally be suitable.

Testing
THIS UNIT CONTAINS DANGEROUS MAINS VOLTAGES. DO NOT OPERATE UNLESS ALL COVERS ARE IN PLACE. MAINS ELECTRICITY CAN KILL. PLEASE BE VERY CAREFUL.

If the unit has been carefully constructed there is no reason why it should not work first time.

Do not plug anything into the master or slave sockets initially. Plug the unit into the mains, via an RCD or earth leakage circuit breaker if possible. The Mains LED (D1) should light and the Slave LED (D5) should remain off.

Connect a table lamp to the master socket and switch it on. The lamp should operate as usual, and the Slave LED should come on when the lamp is on. Now plug a second lamp into a slave socket. This second lamp should come on whenever the first lamp is switched on. Both lamps should be at full brightness and should not be flickering. If the above check is successful, the unit is working correctly, and can be put into use.