switches

タイトルまたは説明

In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the
current or diverting it from one conductor to another. The most familiar form of switch is a manually operated
electro mechanical device with one or more sets of electrical contacts. Each set of contacts can be in one of
two states: either "closed" meaning the contacts are touching and electricity can flow between them, or
"open", meaning the contacts are separated and the switch is no conducting. The mechanism actuating the
transition between these two states (open or closed) can be either a "toggle" (flip switch for continuous "on"
or "off") or "momentary" (push-for "on" or push-for "off") type. A switch may be directly manipulated by a
human as a control signal to a system, such as a computer keyboard , or to control power flow in a
circuit, such as a light switch. Automatically operated switches can be used to control the motions of
machines, for example, to indicate that a garage door has reached its full open position or that a machine
tool is in a position to accept another work piece. Switches may be operated by process variables such as
pressure, temperature, flow, current, voltage, and force, acting as sensors in a process and used to
automatically control a system. For example, a thermostat is a temperature-operated switch used to control
a heating process. A switch that is operated by another electrical circuit is called a relay. Large switches
may be remotely operated by a motor drive mechanism. Some switches are used to isolate electric power
from a system, providing a visible point of isolation that can be pad-locked if necessary to prevent
accidental operation of a machine during maintenance, or to prevent electric shock.Surface mounted devices (SMD) are active and passive electronic components without Conventional
connecting wires.
The SMD components will be placed on the “solder side” of the PCB and their metal caps Soldered to the
copper pads of the PCB. Therefore both layers of the PCB could be used as active areas. A thickness of
PCBs used for SMD is between 0.8 and 1.*0 mm. Historically roots of SMD are hybrid circuits on the
ceramic substrates (middle of seventies) but a huge Industrial applications of SMD started on a begin
eighties.