Tech Tips: What Timer Is It?

May 2, 2019
Timers are an integral part of an access control system, allowing entry and egress on a pre-determined schedule

Outboard timers are devices we use frequently when setting up door controls, automatic locking and security lighting.

Timers are classified by their circuit design feature, form factor and application. So we can see terms like “one shot” (circuit design feature); “module” (form factor); and “door release timer” (application).

Mechanical Daily/ Electronic Daily Event Timers: These rovide the means to turn on and off within a 24 hour cycle. They can be mechanical dials in metal boxes with screwed ON and OFF trips. These often must be hard-wired to line voltage and to the loads they controlled. More up-to-date designs have trippers, male blades so they plug in a receptacle and express the output as a female receptacle for plugging in your load. They are often motor driven dials or solid state with LCD displays.

The considerations for all timers is that they be installed in such a way so they are not exposed to atmospheric conditions for which they are not designed or be subject to being unplugged or tampered with.

Running line voltage wiring and powering devices like event timers is work that requires an electrician’s license or whatever your state/locality requires.

With a license you can obtain insurance and indemnify yourself and your company against possibly getting sued. If an injury or a fire occurs in a building you have ever performed work, and they can prove it, their attorneys will cast out a huge net, and if you do not have a license or insurance, it will not be pretty for you.

If you are not controlling something that runs on line voltage or a line cord, this type is probably not your best choice.

Weekly Event Timers:  These usually electronic and enable setting up schedules which span several days within a seven-day period. You may have the option to set up a block rule for example several days which have the same hours and also days whose schedule is an exception to the rule; and or skip days or require unique ons and offs.

Annual Timers enable you and your customer to mess things up months in advance. It’s happened so often that I would program a building for a the year, and when a special event was approaching the customer would decide they didn’t trust that I had programmed the timer, and try to check the program, then mess it up, then blame us.

When PC-based electronic access control software came into wide use, it meant that indeed timing of many events could be performed using a keyboard, monitor and PC, simpler than via the miniature screens and non-qwerty membrane keypads on many timer modules.

Programming some of these modules is tedious, and if you do not do it often, can be frustrating. It’s similar to trying to write a letter on a full sized keyboard and computer display compared to texting on a phone keyboard, or programming your VCR compared to opening MS Word  on your PC.

Additionally, unlike PC based software, you usually cannot print out or save your work for backup, review or retrieval.

Still, the demand for non PC based, less costly controls continues to flourish and that’s why we’re writing about them. For many customers and many applications, computer software is not acceptable. While home automation applications and hardware are becoming more available, it is still can be difficult and expensive to control locks, lights and other equipment from a computer.

So all of the timers we’ve discussed so far control things based on the time of day, and in some cases the day of the month and what year it is. They have integral real time clocks of some type. They use scheduled events which trigger outputs on the timer.

Timer Features

The following are common timer features.

TOGGLE/ BI-STABLE: A mechanical toggle switch is what is typically used for wall switches. You flip it on and flip it off. The electronic counterpart has different iterations. There used to be mechanical relays which had mechanisms which threw the cradle and contacts into one position when voltage was applied to the coil, then would remain in that position. Voltage would have to be applied to the coil again to reset the cradle.

Continuous voltage to the coil would not have any effect on the cradle, only the incoming voltage pulse. Normal relays switch when voltage is applied to the coil, but they switch back when the voltage is removed. They do not latch.

So a toggle relay behaves like a wall switch; instead of a finger, it uses voltage to the coil to actuate.

TIMED DOOR RELEASE: This is a very common application for timers, since it involves locks, locks are used on doors, and locksmiths work on doors.

Any access control system provides a time door release. The door may be unlocked when a valid credential or valid code is presented.

Frequently EAC systems will use a Request To Exit (REX or RTE) function or button.

The overwhelming percentage of door locks are free egress/failsecure, so an individual can simply approach the door and actuate a lever or pushbar (exit device) and leave.

Where the door lock is an electromagnetic lock, the system is almost always designed so that free egress is also automatic for the majority of applications.

One exception is facilities where Code or the AHJ permits the door to remain locked until a guard, nurse or other authorized individual allows the person to egress. For those applications where a person is trying to leave, they are requesting to exit, and it will be a switch in the locking device or next to the controlled opening, or a motion sensor mounted above the opening designed to unlock the door.

It is not uncommon for premises to have 24-hour perimeter security so that an unauthorized entry or egress is electronically detected and annunciated. Annunciation can be electronic notification to a guard or other designated individual, a local audible alarm, activation of a camera or all the above.

For authorized entries and REX controlled egresses, alarms are suppressed although the door activity may be recorded or logged by the security system.

Receptionist Button: The door may be unlocked when a remote door release button is activated. This function may be used with an EAC, or intercom, or stand alone.

When an EAC controller is not involved, an outboard timer module is often required. How long the lock remains unlocked depends on several factors.

If the lock only allows the door to be opened for as long as the receptionist is pressing the button, the person requesting to leave or enter must respond or the door may relock too quickly, in which case they must request the door be unlocked again. This causes problems and is why timers to extend the unlock time are usually included in the door control system.

The goal is provide a convenient means of transgressing the door, without leaving the door ajar and unlocked longer than is necessary.

This is why a door closer is definitely required so the door will reclose all by itself after someone transgresses it.

This to prevent abuse of the EAC system by individuals slipping in or out of the opening when they are not supposed to.

(Of course if you are dealing with a fire rated door, a door closer is required to satisfy the life safety code.)

The door’s position is monitored with a door position switch (DPS) which is connected to the EAC. How the EAC interacts with the DPS and controls the door lock depends on the type of lock that is being used, but generally, the idea is to relock the door lock as soon as possible, and monitor the door’s position so the system knows when to do this. Often the circuit relocks the door as soon as the door is opened, and the bypass on the alarm remains until the door has reclosed behind the person transgressing the opening.

So a few different timers need some additional functions, and a RESET (RST) function is required.

Timers and Delayed Egress

Delayed egress is a term applied to technology and rules for a special locking arrangements. Delayed egress is often accepted as an alternative to free egress and doors which inhibit free egress. “Often Accepted” means that the AHJ has reviewed the application and provided his approval.

Delayed egress is used in retail to discourage using remote doors to slip merchandise out, or in healthcare to allow workers time to respond to a patient attempting to elope, as two examples.

A delayed egress locking arrangement is built around the timer used to control the different features required. Frequently delayed egress is built into the hardware, such as an exit device or an electromagnetic lock. A delayed egress system can also be built up from component parts.

Over the years that Delayed Egress has been used, different rules have been developed by the Code Writing community such as BOCA, IBC & NFPA to name just a few.

But the delayed egress sequences demonstrate how multiple timers and sensors can be integrated to perform important security and life safety functions.

1. A Nuisance delay timer which inhibits the unlocking of the door or the initiation of the delayed egress timing sequence and provides an audible alarm.

2. A timer that is preset to local code requirements (15 or 30 seconds) and not readily adjustable; once initiated sounds and alarm, provides an external signal for peripheral equipment and ultimately releases the lock on the door allowing egress.

NOTE: This is not the complete specification for delayed egress, just to briefly show timers can be used to perform special applications.

When door operators are used in vestibules and with electric locks and low energy door operators, special timers and timing functions are required. For example often when a door operator is activated, the electric lock on the door must be unlocked before the door operator begins to open the door to avoid the lock jamming or the door operator interpreting the impediment as a person in the door’s path which will cause the low energy door operator to stop to avoid injuring the individual blocking it.

For vestibule doors where two openings with door operators must open in a specific order depending on the direction of travel, timers are sequenced and often timed and monitored so only one door is open at a time in order to prevent heat or cooling loss from the building.

We just touched briefly on timers. If you have any questions you are welcomed to contact us and we’ll do our best to help.

About the Author

Tim O'Leary

Tim O'Leary is a security consultant, trainer and technician who has also been writing articles on all areas of locksmithing & physical security for many years.