Slot Principles I• Switches • Buttons

Switches• Overview

• Used in many devices• Varying levels of complexity of the switch• Varying levels of complexity of the assemblies

• Some common types below

       

Picture by Arnold Reinhold.

Switches• Contacts

• In the simplest case, a switch has two pieces of metal called contacts

• That touch to make a circuit, • That separate to break the circuit.

• The contact material is chosen for its:• Resistance to corrosion, because most metals form insulating

oxides that would prevent the switch from working. • Contact also chosen on the basis of electrical conductivity• Hardness (resistance to abrasive wear)• Mechanical strength• Low cost • Low toxicity[

       

Switches• Contacts

• Sometimes the contacts are plated with noble metals• They may be designed to wipe against each other to

clean off any contamination• Nonmetallic conductors, such as conductive plastic, are

sometimes used.

• Actuator• The moving part that applies the operating force to the

contacts is called the actuator, and may be a toggle or dolly, a rocker, a push-button or any type of mechanical linkage (see photo).

       

Switches• Contact arrangements

• A pair of contacts is said to be 'closed' when there is no space between them,

• Allows electricity to flow from one to the other.

• When the contacts are separated by an insulating air gap, an air space, they are said to be 'open',

• No electricity can flow at typical voltages.

• Switches classified according• To the arrangement of their contacts in electronics fields • But electricians in the electrical wiring service business

use different nomenclature, • such as "one-way", "three-way" and "four-way”

       

Switches• Switches Normally Opened/Closed

• Some contacts are normally open (Abbreviated "n.o." or "no") until closed by operation of the switch

• Others are normally closed ("n.c. or "nc") and opened by the switch action

• Abbreviations given are commonly used on electronics diagrams for clarity of operation in assembly, analysis or troubleshooting

• Changeover switch • Make-before-break switch contact • Break-before-make switch contact

       

Switches• Changeover switch

• Which type is used could be important• If for example, the switch selects two different power sources

instead of switching circuit loads• Or the circuit load will not and cannot tolerate any interruption

in applied power.

• pole and throw are also used to describe switch contact variations • A pole

• Set of contacts, the switch's electrical terminals that are connected to and belong to a single circuit, usually a load.

• A throw • One of two or more positions that the switch can adopt

       

Switches• pole and throw are also used to describe

switch contact variations • A throw

• Which normally, but not always correspond to the number positions the switch handle or rotor can take when connecting between the common lead of the switch and a pole or poles

• A throw position which connects no terminals (poles), has a mis-match between positions and positions which connect terminals

• But are quite useful to turn things "Off" or for example, alternatively select between two scaled modes of operation. (e.g. Bright illumination, moderate illumination, no illumination.)

• Abbreviations for the types of switch in electronics • Such as

• "single-pole, single-throw" (SPST) (the simplest type, "on or off“)

       

Switches• pole and throw are also used to describe

switch contact variations • Abbreviations for the types of switch in electronics

• Such as• "single-pole, double-throw" (SPDT), connecting either of two

terminals to the common terminal• In electrical power wiring (i.e. House and building wiring by

electricians) names generally involving the suffixed word "-way" are used

• Types• SPST

• Single pole, single throw• A simple on-off switch: Example is a light switch

       

Switches• Types

• SPDT• Single pole, double throw• A simple changeover switch: C (COM, Common) is connected

to L1 or to L2• DPST

• Double pole, single throw• Equivalent to two SPST switches controlled by a single mechanism

• DPDT• Double pole, double throw• Equivalent to two SPDT switches controlled by a single mechanism:

       

Switches• Contact bounce

• Also called chatter• Common problem with mechanical switches and relays

• Switch and relay contacts are usually made of springy metals • They are forced into contact by an actuator.• When the contacts strike together, their momentum and

elasticity act together to cause bounce.• The result is a rapidly pulsed electrical current instead of a clean

transition from zero to full current. • The waveform is then further modified by the parasitic

inductances and capacitances in the switch and wiring, resulting in a series of damped sinusoidal oscillations

• This effect causes problems in some analogue and logic circuits that respond fast enough to misinterpret the on-off pulses as a data stream.

       

Switches• Contact bounce

• Solutions• There are a number of techniques for debouncing (mitigating

the effects of switch bounce). They can be split into :• Wet contacts• Timing based techniques • Hysteresis based techniques.

• Wet Contacts• Mercury wetted switch contacts do not suffer from bounce

• as once the connection is made the mercury keeps the contact conducting during mechanical bounce

• Toxic solution• Timing based techniques

• Range from simple RC circuits to digital sampling

       

Switches• Contact bounce

• Solutions• Timing based techniques

• Simple Series resistor and Cap to ground on the Switch input• Schmitt Trigger on the input

• Sample the switch state at intervals longer than any possible train of bounces.

       

Buttons• Overview

• Some common Slot Machine Buttons w/switchs

       

From Suzo-Happ’s Web

Page

Buttons• Overview

• Part of the Button switch assembly that the end user activates

• Can be very simple (below)

• Or Complex like those on a slot machine

• Older style with a lamp shown on the right

       

From Suzo-Happ’s Web Page

Buttons• New Types

• Buttons with LCD displays • Displays can be changed under game control• Promoted on many EGM’s that can support Server Based

Gaming • Example fro Suzo-Happ’s Web site

       

Buttons• New Types

• Started as programmable keys for a keyboard• You can read about the history of LCD Buttons at:

http://www.lcd-keys.com/english/history.htm