Choosing The Access Control Locking System

Most access control articles discuss the installation of access control systems from the point of view of having already chosen the equipment.


Most access control articles discuss the installation of access control systems from the point of view of having already chosen the equipment. For this article, I decided to find an opening needing to be controlled electronically, prior to the decision making process. With the cooperation of...


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Note: For this application, the owner is considering having the SDC 950 EntryCheck mounted onto the interior side of the glass wall adjacent to the door as the reader has a six inch read range. Locating the 950 EntryCheck on the interior has several advantages as access can still be gained using a proximity card or fob. Additional advantages include the reader is protected against weather and vandalism.

For sensor activated egress, SDC recommends the SDC MD31D Series Request to Exit Sensor (REX) to satisfy I. B. C. requirements for 1008.1.3.4. The MD31D sensor will be mounted on the wall surface or ceiling without modification in proximity to the exterior door inside a building. The Request to Exit sensor shall provide free exit to individuals within the building without causing an alarm. The Request to Exit sensor will operate using Passive Infrared (PIR). The SDC MD31D is listed by Underwriter ’s Laboratories under UL 294-Access Control System Units, FCC Part 15,C22.2 No.205-M1983-Signal Equipment and CE.

The “U” shaped PIR coverage field is created by the eight beams produced by the SDC MD31D. The shape of the coverage field can be adjusted to provide precise target area detection. In addition, the height and angle of the PIR determines the field size and distance from the wall. For this opening, the SDC MD31D can be mounted onto the header above the middle of the door. At this position, the beam can be adjusted from approximately 1.5 feet away from the door to six feet away. At the angle closest to the door, the width of the beam is at least four feet, more than sufficient to cover our single door opening. At six feet, the width is approximately eight feet, sufficient for double entry doors.

The SDC MD31D features a one-half to 64 second relock delay controlled by three switches. When a person enters the motion detection field, the Sensor interrupts power and the Fail Safe operation mode releases the lock. The MD31D code compliant Passive Infrared Egress Detector is available in a white or black housing.

The SDC MD31D has been designed to protect against a variety of unwanted activations. The SDC MD31D uses a balanced dual opposed element detector to guard against unwanted activations caused by changes in infrared energy not associated with motion. RFI protection guards against false activations caused by radio frequency interference. There is a dual slope temperature compensation circuit that increases detection capability under high temperature conditions where the background temperature is similar to that of the human body.

As a backup against electrical problems, International Business Codes 1008.1.3.4, requires that doors shall be arranged to unlock from a manual unlocking device within five feet of the secured door. Ready access shall be provided by a manual unlocking device.

To comply with this code, Security Door Controls recommends using the SDC 413MNU Request-To-Exit Switch designed for narrow frame mount applications. This exit switch complies with national fire and building code requirements for manual releasing devices. The SDC 413MNU 1-3/4” by 1” button is clearly identified by a green sign that reads “PUSH TO EXIT”. For wall mounted applications, the SDC 423MU single gang wall mount switch assembly is recommended.

When pushing the button, the door lock power is interrupted and unlocked for 30 seconds. If the button is pushed again within the unlocked period, the 30-second timer cycle is restarted. This 35mA switch operates at 12 or 24 VDC. The 413MNU is California State Fire Marshal Listed and Enterprise Engineering Laboratory Listed.

To power the magnetic lock, reader, sensor, and exit switch, SDC recommends using the UL Listed SDC 602RF Power Supply, a one amp 12/24 VDC filtered and regulated power supply with battery backup. The 602RF has field selectable 12/24VDC output. It has an isolated battery charger that operates off a separate circuit enabling this power supply to provide one amp power.

The Class 2 Outputs on the SDC 602RF power supply indicate that conduit is not required from the power supply to the lock. Power supplies that are not Class 2 would require conduit from the power supply to the lock. Additionally, SDC UL listed Class 2 power supplies can be ordered with a six foot power cord to plug directly into a 115VAC wall outlet. This can eliminate the need for conduit for the 115VAC power supply input.

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