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Introduction to Electronic Access Control. Basic Electricity, Electric Locking Hardware and Access Control Systems. By Paul Chandler of IDN–Inc. What Is Electricity?. Movement of “free electrons” between atoms. What is Electricity?.
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Introduction to Electronic Access Control Basic Electricity, Electric Locking Hardware and Access Control Systems. By Paul Chandler of IDN–Inc.
What Is Electricity? • Movement of “free electrons” between atoms
What is Electricity? • The tendency to inhibit the movement of free electrons is called “resistance” • Some elements are good “conductors” • Some elements are poor “conductors”
What Is A Circuit? • Power Source • Load • Conductors • Switches
Basic Circuit + Load Power Supply - Switch
Ohm’s Law • E = I X R • E is Electromotive Force or Volts • I is Current or Amps • R is Resistance or Ohms • Ohm’s Law is an Equation
E I R Ohm’s Law
Power Formula • P = I X E • P is Power or Watts • I is Current or Amps • E is Electromotive Force or Volts • Power Formula is also an Equation
P I E Power Formula
AC and DC • DC is Direct Current – Electrons move in only one direction • AC is Alternating Current – Electrons change direction 120 times a second
DC - Direct Current + DIRECT CURRENT Load Power Supply - Switch
AC - Alternating Current + ALTERNATING CURRENT Load Power Supply - Switch
AC and DC • AC is distributed by the power company • AC is safer at high voltages • DC is produced by a battery • DC produces a stronger electromagnetic field
Transformers • Used to reduce voltage • Class 2 transformers are power limited • Internal fuse or circuit breaker prevent too much current flow • Choose between “plug-in” and “wire-in” • Specify Voltage and Power, expressed in “VA” volt-amps
Power Supplies • Convert AC to DC • Regulate voltage output • Filter noise and ripple • Over-current protection • Battery charge circuit
Batteries • Sealed, rechargeable battery • Rated by volts and “Amp-Hours”
Batteries • Connect batteries in “parallel” for more amp-hours Charger +- PARALLEL BATTERIES 8 AMP-HOURS + - 12VDC 4 AH Battery + - 12VDC 4 AH Battery
Batteries • Connect batteries in “series” for higher voltage Charger + - SERIES BATTERIES 24 VDC + - 12VDC 4 AH Battery + - 12VDC 4 AH Battery
Circuits • Closed Circuit: Current can flow + CLOSED CIRCUIT Load Power Supply - Switch
Circuits • Open Circuit: Current flow is interrupted + OPEN CIRCUIT Load Power Supply - Switch
Circuits • Short Circuit: Unintended current path, parallel to load, low ohms / high amps + SHORT CIRCUIT Load Power Supply - Switch
Circuits • Series Circuit: Two or more loads in series Load 1 + SERIES CIRCUIT Load 2 Power Supply - Switch
Circuits • Parallel Circuit: Two or more loads in parallel + PARALLEL CIRCUIT Load 1 Load 2 Power Supply - Switch
Parallel and Series Loads • Two or more loads (or resistors) in series: Add the ohms. Load 1 + 2 OHMS SERIES CIRCUIT Load 2 Power Supply 4 OHMS 6 OHMS - Switch
Parallel and Series Loads • Two or more loads (or resistors) in parallel: Add 1/R1 + 1/R2 +1/R3 = 1/Rtotal + PARALLEL CIRCUIT Load 1 Load 2 Power Supply 1.3 OHMS 2 OHMS 4 OHMS - Switch
Electrical Diagrams • Schematic: Shows interconnection of various components + PARALLEL CIRCUIT Load 1 Load 2 Power Supply - Switch
Electrical Diagrams • Riser: Shows wire requirements between components POWER SUPPLY 22AWG 6 COND. SHIELDED 18 AWG 2 COND. ACCESS CONTROL PANEL CARD READER ELECTRIC STRIKE REMOTE RELEASE
Electrical Diagrams • Elevation: Shows relative placement of components PIR INSIDE OUTSIDE MAG CARD READER REX 42” 42”
Voltage Variables • Voltage Drop: Change in voltage caused by resistance of conductor or load • Brownout: Voltage reduction caused by demand on the circuit • Spikes: Momentary high voltage, often related to lightning • Inductive Kickback: Spike caused by collapsing magnetic field
Wire and Cable • Solid or Stranded conductor • Conductor thickness measured in AWG smaller number = thicker conductor • Insulation material determines “general purpose”, “plenum” or “riser” cable • Shielded cable protects data from interference
Multi-Meters • Voltage tested on “live” circuit in parallel with the load + VOLTAGE Load Power Supply - Switch
Multi-Meters • Amps tested on “live” circuit in series with the load + CURRENT Load Power Supply - Switch
Multi-Meters • Ohms tested on “dead” circuit in series with the load Continuity checks for a closed circuit + RESISTANCE Load Power Supply - Switch
Switches • Used to open or close a circuit • Maintained switches can be toggled from open to closed, etc. • Momentary switches return to a “normal” open or closed condition
Switches • SPST = Single pole, single throw • SPDT = Single pole, double throw SPST SPDT
Switches • DPST = Double pole, single throw • DPDT = Double pole, double throw DPST DPDT
Switches • Use a double pole exit switch for “Double Break” lock control Mag Lock DOUBLE- BREAK R E X Access Control Panel Power supply nc c c nc
Switches • Fail Safe locks require normally closed switches in series + Fail Safe Power Supply - N C Switch N CSwitch
Switches • Fail Secure locks require normally open switches in parallel + Fail Secure Power Supply - Switch
Relays • Relays are electrically operated switches • “Form C” relays are SPDT switches • “Dry Contact” relays have electrically isolated coil and contacts. • Latching relays stay activated until reset
Relays • Relays are used in all access controllers • Relays can be radio-controlled • Relays are included in passive infrared motion detectors for egress control • Relays are built into touch-sensitive exit bars
Timers • 7-Day / 24-Hour timers used to schedule door locking/unlocking • Delay timers used to keep door unlocked without holding in a switch • All access controllers have delay timers • Some access controllers have scheduling timers
Electro-Mechanical Locks • Solenoid-Operated bolts • Cabinet locks • Electrified locksets • Electric latch retraction panic devices • Electric trim for panic devices • Strike actuated mortise locks
Electro-Mechanical Locks • Disadvantage: Mechanical wear • Disadvantage: Binding under load • Disadvantage: Power out to the door • Advantage: Mechanical egress • Advantage: Hardware compatibility • Advantage: Use on fire-labeled doors
Electro-Magnetic Locks “Mag Locks” use pure magnetism to secure a door or gate Options include door status and bond sensing circuits
Electro-Magnetic Locks Available in 600 to 2000 pound models
Electro-Magnetic Locks • Inswing doors require special hardware
Electro-Magnetic Locks • Shear locks are used for sliding and double-acting doors • Movable strike plate interlocks with magnet surface
Electro-Magnetic Locks • Disadvantage: Switch required to exit • Disadvantage: Aesthetically unattractive • Advantage: Easy to install • Advantage: Low power requirement • Advantage: Inherently Fail Safe • Advantage: Excellent physical security
Electric Strikes • Companion to mechanical lock • Available Fail Secure or Fail Safe • Disadvantage: Lower physical security • Disadvantage: Difficult to install • Advantage: Mechanical egress • Advantage: Aesthetically neutral • Advantage: Retain mechanical key