Troubleshooting Electronic Access Control Systems

Troubleshooting is an essential skill for those installing as well as servicing electronic access control systems. Although visual observations are an excellent place to start, getting some background on an installation before you even head out is also helpful.

Before you leave the shop:

1. Know which mechanic’s skill set will be best suited for a particular situation;

2. Download installation instructions for the equipment on site;

3. Get some information on the age, and service/performance history of the system (may be on file if you installed or previously serviced the system).

When you do installations, sometimes the troubleshooting begins as soon as the last connection has been made and power is first applied to the system. Click: Nothing happens, (or the wrong things happen.)

Electronic access control systems are comprised of certain essential circuit elements:

  • The Power Supply,
  • The Wiring,
  • The Controls,
  • The Locking Device (a/k/a the load)

Access control systems have at least one power supply for the controller, and possibly another for the locking system, and in some cases an additional power supply for a special purpose reader or other device. Sometimes a single power supply will operate everything. I refer to DC (Direct Current) output sources as power supplies, and AC (Alternating Current) sources as transformers. Wall-mount plug-in power sources are convenient and do not require an electrician to install.

Issues can arise when these wall warts are accidentally unplugged or if the receptacle happens to be controlled by a wall switch or may be turned off unexpectedly by well-intentioned conservationist trying to save electricity.

Hard-wired, power supplies have a metal enclosure and can be outfitted with a line cord or an electrician can hard-wire it to a suitable branch circuit. With a metal enclosure, you can put other accessories such as relays or timer modules inside, or you can get a power supply with Fire Alarm interface or battery backup.

Wiring is still used on most electronic access controls.

Standalone Electronic Access Control is one notable exception. These devices have their own integral power (battery or magneto) integral reader or keypad, integral locking device, and integral logic controller. Standalone access has traditionally not been capable of real time alarm reporting, logging, adding and removing credentials or remote release without wiring. Some models require the use of a handheld programmer.

But that is changing with the introduction of wireless network to enable these features One example is the ALARMLOCK NETWORX.

We also can use wireless remote release buttons with certain standalone access controls equipped to accept remote release triggers. Otherwise your access controls will require wiring for power, video/data, control, and switching purposes.

Your power wiring will be for the reader, the controller or the locking device and is a prime suspect as a source of trouble. Assuming you’re power supply is working and properly rated for the application, and your locking device is working, adequately powered, and properly isolated, then your voltage levels may be low due to that old gremlin, voltage drop.

Voltage Drop

Voltage Drop is present in all circuits, but it is not always a problem. Problems occur when the system design does not take the voltage drop into account when selecting wire gauge, equipment, or equipment locations.

When designing the system, voltage drop calculations should be used as a guide to selecting the correct wire gauge, and perhaps locating power supplies. In some situations, increasing the wire gauge will not be enough and the solution will be to shorten the wire run by relocating the power supply to a point closer to the load.

Voltage drop can become a problem, perhaps an intermittent problem, after the system has been deployed.

EXAMPLE: We added two new access control doors to an existing four-door system which had been in service for about five years. Originally the system designer did the calculations and specified the correct wire. During the upgrade the installers did actual voltage measurements during system deployment, but still a problem was reported the day after the new doors were turned over the doors to the customer.

It turned out that the power supply backup battery was worn out and was consuming power rather than reinforcing it. The voltage at the furthest door was dipping down to the marginal level and our equipment was operating erratically. A new battery resolved it.

During troubleshooting, this battery was reading low even while connected to the trickle charge and it would not have powered the system in the event of an interruption of, or dip in line voltage to the system power supply.

Cabling

Access control cabling could include voltage outputs to electric locking devices and fire alarm interfaces. Shorts, opens or weak connections on these cables of course can result in problems.

When setting up systems, I always include a slave relay. They provide electrical isolation between the control and on board output contacts and the electric locking device. The relay’s contacts actually switch the voltage to the lock, protecting the controller from possible noise kickback, and also from the damage to the contacts repeatedly energizing the electric lock. Should there be a problem with the lock or a short somewhere in the control circuit, the relay contacts will take the hit rather than components on the controller. It is cheaper and easier to replace a relay than a controller.

The relay coil is what the controller has to energize. Relay coils are low current, usually under 50 mA. Electric locks and maglocks draw more current and are typically inductive loads throwing spikes and surges back across the controller’s contacts if the lock is direct wired to them. Varisters and diodes are used to suppress the noise, but it is better to isolate your circuits and use suppressors as well.

Relays cost around $10. Diodes and varisters are often provided with locks and controllers or can be purchased inexpensively.

Switching/Signaling Cabling might include things like Request to Exit switches and door position sensors. Door position sensors usually do not carry current. Request to Exit sensors and pushbuttons may or may not switch the lock power.

Where maglocks are used, it has been recommended practice or mandated by code to provide redundant life safety to door systems by using the REX as an additional means to cut power to maglocks so emergency egress can be assured even if other system elements fail to operate. So if a maglock is not operating properly, the REX may be the culprit and needs to be tested as part of the troubleshooting process.

Voltage (AC & DC) is the amount of charge between the sides of the circuit, the electrical force, or “pressure”, that pushes current through wires. It is measured in VOLTS (V or E).

Current (Amps) is the movement of electrical charge (electrons) in a circuit, similar to water through a hose. The rate at which electrons flow through a circuit is measured in AMPERES (AMPS, A or I)

Resistance (Ohms): is the limiting of electrons that pass through a circuit, adding resistors or changing wire size limits the rate of electrons moving through the circuit. Measured in OHMS ( ? or R ).

Power is measured in Watts. May also be represented by (P). P = I x E

 

Troubleshooting Tools: Multimeters, Toner/Tracers

Multi-Meters are probably the technician’s most versatile troubleshooting tool, used to measure voltage, resistance and current.

There is an endless debate over which meter is best and how much it is necessary to pay in order to buy a good meter. For me a meter has to be Accurate, rugged enough to withstand falls and abuse, convenient to operate with an easy to read display and operate control face, and be adequately insulated to protect me from electric shock. My Fluke 112 is not the top of the line, or the latest model, but it serves me well, and has for at least a decade. Multimeters are used to measure voltage, resistance and current.

Toner/Tracers can be life savers in a variety of scenarios. A toner/tracer such as the Fluke TC90 is a multi-function tool capable of three functions:

  • Fault locator (finds the distance to opens or shorts on electrical wire, telephone wire, security wire and coax.)
  • Cable and wire manager (measures up to 2,500 feet)
  • Tone generator with SmartTone technology which positively identifies the correct traced wire.

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