Page 86 - Electromechanical Devices and Components Illustrated Sourcebook

48 Electromechanical Devices & Components Illustrated Sourcebook

A type of selector switch that most of us are familiar with tens-of-thousands of volts and have excellent, high-voltage
is the automobile ignition distributor, as shown in Figure 4-38. terminals. Additionally, spark plug wires are a low cost source
The distributor is used to select the appropriate spark plug for for high-voltage wire and connectors. When using a distribu-
ignition on internal combustion engines. It should be noted tor for a selector switch, the housing should be grounded for
that a common distributor can be configured to serve as a high- safety. The contact in a standard distributor is a spark gap
voltage selector switch. Distributors are designed to switch arrangement so a hard contact must be added to the rotor. A
knob, detent, and indicator replace the timing gear.
Figure 4-39 shows an automobile distributor configured
Common (Coil)
as a high-voltage selector switch. The timing gear is
Spark Plug Terminals removed and replaced with a panel and selector knob with
pointer. The housing is drilled and tapped for a ground wire,
as shown.

Cap
Limit Switches

Limit switches are a type of switch that is specifically
designed to detect machine motion. They are available in vari-
ety of sizes and configurations. They usually incorporate a
Rotor single-pole, double-throw, snap action switch element. The
principal difference from limit switches are their actuators.
Contact These range from micro buttons to rather sophisticated spe-
Breaker Plate cialty actuators. A common example of a limit switch is the
Housing button that turns on the light in your refrigerator or car when
you open the door.
Label
Figure 4-40 shows an example of some of the common
direct-acting actuators, the micro button and standard button
Shaft Housing
being the most common. Figure 4-41 shows common lever
arm actuators. Like the direct-acting actuators, lever arms are
Clamp Lip
extremely common.
Different manufacturers offer a variety of specialty actu-
Mount
ators and are configured for nearly every conceivable appli-
cation. Figures 4-42 and 4-43 show just a few specialty
actuators.
Timing Gear

Figure 4-38 Automobile Ignition Distributor

Spark Plug Wires
Wire Boots Selector Knob
Outputs Mounting Holes
Cap
Pointer Panel
Panel Mount Pointer
Housing
1
6 2

Common
5 3
4
Set Screw
Panel Selector Knob

Outputs
Ground
Figure 4-39 Distributor High-Voltage Selector Switch