Fig. 4.6 Fig. 4.7 4.1.5.4 LCD Interfacing diagram The diagram below gives the interfacing configuration of the LCD with the microcontroller. Energy Metering Circuit: This enrgy meter is manly built around the IC 7751, an ANALOG DEVICE ELECTRONIC ENERGY METERING IC, which converts the analog input energy reading into output as pulse for displaying the count value which is equivalent to the energy consumption. In addition to monitoring the energy consumption and data transmission & reception, the meter also provides protection against high voltage, over current and theft by immediately disconnecting metering circuit from the supply and altering the consumer by giving an audible alarm, so that the consumer or maintenance personal to take corrective action. This circuit takes two current samples in terms of voltage form then takes one voltage sample, and then generates a series of pulses depending upon the load connected. It contains analog to digital converter section internal to it, and it also ahs its own reference, it work s on the fixed frequency source generated by the crystal connected to it externally. There is also fault detection facility provided in the metering IC, So whenever the two currents i.e. Phase and neutral, differs by the value more than 12% fault indication is provided.
Disadvantages:- It requires four diodes. As during each half cycle of A.C. input, two diodes are conducting therefore voltage drop in internal resistance of rectifying unit will be twice as compared to center tap circuit. Filter Circuit :- Generally a rectifier is required to produce pure D.C. supply for using at various places in the electronic circuit. However, the o/p of rectifier has pulsating character i.e. if such a D.C. is applied to electronic circuit it will produce a hum i.e. it will contain A.C. and D.C. components. The A.C. components are undesirable and must be kept away from the load. To do so a filter circuit is used which removes (or filters out) the A.C. components reaching the load. Obviously a filter circuit is installed between rectifier and voltage regulator. In our project we use capacitor filter because of its low cost, small size and little weight and good characteristic. Capacitors are connected in parallel to the rectifier o/p because it passes A.C. but does not pass D.C. at all. Three terminal voltage regulator :-
Plate resists Solder stop lacquers Notation printing In its basic form, the screen-printing process is very simple. A screen fabric with uniform meshes and opening is stretched and fixed on a solid frame of metal or wood. The circuit pattern area open, while the meshes in the rest of the area is closed. In the actual printing step, ink is forced by the moving squeeze thorough the open meshes onto the surface of the material to be printed. The ink deposition, in a magnified cross section, shows the shape of a trapezoid. Pattern transfer onto the Screen There are two different methods in use, and each method has its own advantages and disadvantages. With the direct method, the screen is prepared by coating a photographic emulsion directly onto the screen fabric and exposing it in the pattern area. The indirect method makes use of a separate screen process film, supported on a backing sheet. The film on its backing sheet that is there after pressed onto the screen fabric and sticks there. Finally, the backing sheet is peeled off, opening all those screen meshes, which are not covered by the film pattern. The direct method provides very durable screen stencils with a higher dimensional accuracy but the finest details are not reproduced. The indirect method is more suitable for smaller series and where the finest details to be reproduced. The indirect method is faster but dimensionally less accurate