An Experiment with Hinges and Door Contacts

When dealing with Orange County card access systems, applying card access to a single wood door with mortise or cylinder, the idea of finding a way to read door status at the transfer hinge is attractive because (1) the labor of running wire to the overhead for a flush-mounted magnetic switch is avoided; and (2) if an authorized-exit lock body is used then all wire that goes to the door frame would go to the same place, the transfer hinge.

At an additional cost of $25 I found I could procure a magnetic switch that installs into fastener holes in the transfer hinge and is designed to look like the head of a standard #3 Phillips fastener when installed. A pilot hole is drilled in the door, and the fastener is tapped into the hole. On the jamb side, the corresponding fastener hole is drilled through the jamb and a magnetic switch part is installed, with its wires leading to the area in the wall where transfer hinge terminations are made up.

On paper, this looked attractive: for retro-fitted doors, about 10% of door-switch installations in the jamb have more labor than you would think due to hidden features of the wall’s framing, and picking up a magnetic switch at the transfer hinge means that the wire run is virtually free because wire is inevitably pulled there for the mortise lock control.

When this idea was moved from the theoretical to the real world, my results were negative. The switch product turned out to be quite delicate. When installers tapped the switch and its magnet into the pilot holes, a certain percentage were damaged. This only became apparent when the commissioning tests for the door were performed, showing up as extra labor to trouble-shoot and correct the problem. This occurred on maybe 20% of the doors in the pilot project. It is possible that with practice the installation crews could have done better, but given the additional cost of the switch I decided to abandon the effort.

I have also identified a transfer hinge with the doors status capability built in to the hinge. This will cost an additional $50 and has an adjustment at the hinge for sensitivity. I haven’t tried this one yet.

Card Access Installation: Request-to-exit

A standard feature of a card access controller is the “request-to-exit” input. When a controlled door is opened from the secured side (inside), the card access system detects the open door condition with no corresponding access event from the card reader. The request-to-exit (REX) input is activated to inform the card access system that the event is an authorized egress rather than a forced entry condition. Traditionally, this is accomplished by installing a passive infrared motion detector (PIR) in the ceiling on the inside of the door.

An alternative approach is to specify request-to-exit contacts (often called “authorized exit” by lock manufacturers) be included in the lock body when purchased. The advantages are these:

• Eliminating the PIR will eliminate (1) the need to wire power the PIR; (2) the need to provide a separate mounting location in wall or ceiling; (3) start-up labor to adjust the PIR; and (4) will simplify and streamline maintenance over the life of the project.
• Adding authorized exit means all wires at the door will pass through the transfer hinge and terminate at the lock body with the exception of the door switch. There is no adjustment.

In obtaining these advantages, the only penalty incurred is increased cost of the lock body. For the installer, this is offset by reduced labor in installation and commissioning. For the client, the advantage is a cleaner installation that will be more maintainable over the project life.

Authorized exit is available on mortise locks, cylinder locks, and panic hardware as an option. All these mechanisms share the common feature that their mechanism offers egress through the secured door. In the case of magnetic locks, this feature does not exist. Thus for magnetic lock applications, a PIR will still be required to request-to-exit functionality.

Sharing RS232 Communication Among Several Devices

A not uncommon field challenge is to establish two-way communication from a central device to a group of slave devices. An example would be a central system connected to a group of field controllers. If these controllers are distributed via telephone lease-lines, then one will typically find a single RS232 device that needs to communicate to multiple RS232 modems. This presents a problem, because the RS232 signal was not designed to allow devices to be wired in parallel. The quiescent state of the XMT line is nominally -12v, so paralleling multiple devices will cause the inactive devices to mask communication from an active device. This occurs because the RS232 active signal must be pulled positive to a nominal 12v, but at least 3v. The brute force solution to this problem is to procure a piece of hardware that accepts one RS232 source and parallels it to four or eight RS232 ports. The disadvantage of this is (1) the cost of the additional hardware; and (2) the additional complexity it adds to the communication network.

An alternate solution is to put diodes on the slave device XMT line. However, the front-end device will need to see some of the negative voltage that is blocked by the diode. Therefore, one of the slave devices will have a resistor in parallel with the diode: this supplies the required negative voltage to the front-end device, but will not interfere with an active device’s communication. In general, any slave device may be chosen to accept the diode, but one could measure with a DVM to find the device whose quiescent signal is most negative and select that one by preference. A value of 1K ohms seems to work fairly well for networks with two to four devices. It is possible that with many devices the value would need some tweaking, but I have never needed to do so.

Sielox Releases Pinnacle 6 Access Control System

Sielox, a leader in Electronic Access Control Security Systems has introduced Pinnacle 6, the first release since the Agile Methodoloy was adopted. Pinnacle's integration with the Aegis2 software package allows security systems such as CCTV, access control, digital video recorders (DVR's), and intercoms systems to be combined to form a truly integrated security system.

New Pinnacle 6 Features Include:

• Aegis2 Integration (DVR, CCTV, Intercom and Graphics)
• Support for X-LAN (Up to 32 doors per LAN connection)
• Card Holder Quick Entry Tab
• First Person Rule (Snow Day)
• Card ID Decimal Entry
• User Actions from the Event Grid
• Tree Find (Find Devices in the Device Tree)
• Easy Network Set-up (UDP / TCP) Selectable

For more information click: Pinnacle 6 Release Notes

(Contact Diversified Automation at 714-522-3303 for more information)

ASIC/1-8755 Controller

The ASIC/1-8755 is a pre-programmed communicating digital controller for the control of zone volume or pressure tracking with pressure independent Variable Air Volume (VAV) terminal units. The controller includes two on-board airflow sensors - one controller handles both supply and exhaust boxes.

This pressure independent controller is mounted on the primary VAV terminal that is used to maintain the space temperature. The second airflow sensor monitors the exhaust airflow volume. The controller monitors exhaust volume and modulates the exhaust damper at the exhaust box to maintain a predetermined positive or negative zone pressure or exhaust volume differential. The controller has personalities for cooling only, and cooling with hot water or electric reheat. A three-position switch allows positive, neutral, or negative zone pressure control.