Keri Systems SB-293 - Manual (Page 23)

Keri Systems, Inc. Technical Reference Manual – PXL-250 and SB-293
Revision 5.5 P/N: 01836-004 Page 23
Only commercially built, linear, regulated power supplies should be used with
any access control system using proximity readers.
When installing a power supply for the PXL-250 controller, mount the power supply
three feet or greater from the controller to provide a degree of isolation from EMI that
may be generated by the power supply.
6.2.2 EMI Sources
Keri Systems also recommends installing the controller in low EMI areas whenever
possible. Always be cognizant of sources of EMI that may affect the operation of the
PXL-250 controller and install your controller away from these sources. Common
sources of EMI include computer monitors, electric motors, power transformers, and
air conditioning and heating units.
6.2.3 Separating Power Cables from Network and Reader Cables
To prevent EMI that may be conducted between power cables and network/reader
cables, Keri Systems recommends running the power cables apart from the network
and reader cables. This will minimize the possible effect a voltage surge on the power
cable may have on the network and reader cables.
6.3 Transient Suppression
Voltage transients are electrical surges or spikes conducted through power, input, or
output lines. Transients are generated when electric devices (such as electric locking
devices) are turned on or off. Transients may affect the operation of both the PXL-250
Controller and SB-293 Satellite board. Because of this, transient suppression is
required for both devices. A transient suppressor is a device added to an electrical
circuit that minimizes the affects of transients. Depending upon the application, a
transorb or an isolation relay provides the suppression necessary to ensure proper
operation of the access control system.
Under normal circumstances, a 1.5KE39C transorb must be installed across the
positive and negative power lines at the electric locking device to provide the best
operating conditions for the PXL-250 or SB-293. This transorb will minimize any
transients that may be generated by an electric locking device from affecting the
operation of the PXL-250 or SB-293. Two bipolar transorbs are provided with each
PXL-250 and each SB-293 for this purpose.
In applications such as parking gates or turnstiles (or any application using a large
electric motor), a transorb alone may not provide enough suppression; an isolation
relay may be required. Keri Systems offers an Isolation Relay Package (Keri Systems
P/N IRP-1) which can provide suppression for the large transients generated by these
types of devices.