Class Notes - Year 4 - 2020-2021
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Year 4

Lesson 404

Timing Relays: On-Delay, Interval, and Recycle

ECM5 16-1 - Timers

4 categories
Dashpot
Oldest type
Rarely used in new installs
Synchronous clock
Still specified in some new installs
Solid-state
Most common stand alone used today
Solid-state programmable
In most systems containing programmable logic relays, this type can replace any other type
Dashpot, synchronous clock, and solid-state are stand-alone
Standalone timers are physically connected between input device and output device
Solid-state programmable are functions included in electrical motor control devices

Dashpot

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Synchronous Clock Timers

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Maintain speed based on frequency of AC power

Solid-State Timers

Time delay provided by solid-state electronics
Accurate
economical cost
Ranges from fractions of a second to hundreds of hours
Designed for plug in modules for quick replacement
Can replace dashpot and synchronous timers

Solid-State Programmable Timers

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Programmed with PLR (PLR has input, output, and programming section)
Programming section
PLRs typically include at least 12 timers
Real time clock can incorporate specific days and times
Input section
Digital on/off, open/close switches are connected
Often includes analog input section
Output section
Loads are connected
Provides either mechanical switches or solid-state output contacts

ECM5 16-2 - Timing Functions

Types

On-delay
Off-delay
One-shot
Recycle

On-Delay Timers

Delay-on-operate
Preset time period must pass after timer coil is energized before action occurs on contacts
After contacts change position, they stay until coil loses power
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On-Delay (Timed-Closed)
After set time, contacts close
On-Delay (Timed Open)
After set time, contacts open
On-Delay Timer Applications
Monitor patients breathing
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Off-Delay Timers

Does not start timing function until power is removed
When power is applied to coil, contacts change
When power is removed, aftertime period, contacts return to normal
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Off-Delay (Timed-Open)
Provide cooling in a projector
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Off-Delay (Timed Closed)
Provide pumping system with backspin protection and surge protection on stopping
Applications
Pumping System
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Emergency industrial shower
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One-Shot Timers

Interval timer
Contacts change position immediately when coil is energized
Remain changed for set period of time
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Examples
Coin operated game
Dryers
Car washes
Available since solid-state timers came out
Applications
Amount of time plastic wrap is wound around pallet
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Recycle Timers

Contacts cycle open and closed repeatedly once timer receives power
Continues until power is removed
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Symmetrical
Equal on/off periods
Asymmetrical
Independent adjustment for on and off
Applications
Product mixing
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Multiple Function Timers

Solid-state timers that that perform many different functions
Usually set by dual in-line package (DIP) switches
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Timer Comparison


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Timer Diagrams

Allen-Bradley & SSAC Overview

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Allen-Bradley Timer

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Allen-Bradley - Power Only

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Allen-Bradley - Power and Control

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SSAC

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SSAC - Power Only

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SSAC - Power and Control

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IEC Manual 404

Typical time adjustment ranges

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Base Configuration

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