Digital Alarm Clock-- Based on a PIC micro （4）

Published:2011/7/22 2:12:00 Author:Li xiao na From:SeekIC

by M. Conde de Almeida

Construction

The artwork of the PCB designed for the clock is shown in Figure 3. The PCB has to be cut in two to separate the main board from the display board.



Start by soldering the wire links onto the main board. Then follow the five IC sockets and all low-profile components. The rest of the construction should be mostly plain sailing as only regular components are used. As always, take care with the polarity of electrolytic components like capacitors, diodes and (yes!) the displays. The display board is secured to the main board at an angle of 90 degrees. The interconnections between the boards are made using angled SIL pin-headers or 40 short pieces of stiff, bare wire. The pushbutton actuator rods will protrude a little above the display tops to make them accessible from the outside once the PCB assembly has been mounted behind the front panel. A red bezel may be used as a finishing touch to enhance the appearance of the clock.

Using a multimeter, make sure that there’s no short circuits between the +5 V supply rail and ground.

When inserting the integrated circuits always check the correct ’pin 1’ position. Finally, avoid ESD damage to your circuit by keeping yourself grounded by means of wrist straps.

Clock operation



The Time adjustment is shown pictorialiy in Figure 4. Other drawings are available but not printed here for lack of space. They include:

- clock display;
- keys and their functions;
- alarm on/off key operation;
- buzzer control procedure;
- operation in battery mode (mains power failure);
- alarm adjustment,

The pictures are supplied in the form of a (zipped) pdf document — see this month’s Free Downloads, number 030096-12.

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