DESIGN CONSTRUCTION AND IMPLEMENTATION OF A TOUCH SENSITIVE SWITCH

ABSTRACT A switch is an imperative constituent of any electronic or electrical circuit. It can either be mechanical, electro-mechanical or electronic. Mechanical and electro mechanical switches are prone to wear and tear with time. The introduction of semiconductors has led to the invention of electronic switches that are more efficient, fast and durable. Further development of electronic switches led to the production of touch-sensitive switches. This project is based on the design and construction of a resistance touch sensitive switch; Implemented on an alarm circuit which was designed to buzz at a frequency of 1.533Hz, duty cycle of 50% and powered by a 9v battery. Aluminium foils were used as the touch plates-A pair to turn it ON (ON pair) and another, to turn it OFF(OFF pair) with both pairs sharing a common plate. Touch plates are usually of an adequately large surface area that can accommodate a finger so as to enhance their sensitivity. This touch switch is recommended for use on household gadgets and lighting switches. It can also be used to switch an AC load, with the use of a relay of appropriate rating.

LIST OF FIGURES                         Page Figure

1.1    Diagram showing a transistor as a switch.      

Figure 2.1    Schematic symbol for a toggle switch.     

Figure 2.2   Schematic symbol for a push button switch.     

Figure 2.3   Schematic symbol of a selector switch.     

Figure 2.4   Schematic symbol for a joy stick switch.     

Figure 2.5   Schematic symbol of a lever actuator switch.     

Figure 2.6   Schematic symbol of a proximity switch.     

Figure 2.7   Schematic symbol for a speed switch.     

Figure 2.8   Schematic symbol for a pressure switch.     

Figure 2.9   Schematic symbol for a temperature switch.     

Figure 2.10   Schematic symbol for liquid level switch.     

Figure 2.11   Schematic symbol for a liquid flow switch.     

Figure 2.12   A circuit symbol of a relay.       

Figure 2.13   Cut-out diagram of a vacuum tube       

Figure 2.14   Schematic symbols for NPN and PNP transistors.     

Figure 2.15   An illustrative circuit for transistor switching.     

Figure 3.1   Resistance Touch Sensitive Switch Circuit Diagram     

Figure 3.2   Alarm Circuit.         

Figure 3.3   Resistance Touch Sensitive Alarm Circuit Diagram.     

Figure 3.5   Components layout.