Apollo AAN-1, Hardware Manual, Page: 20 / 70

15 AAN-1 & AAN-2 Hardware Manual
© 2011 Apollo Security Inc.
3 System Wiring
SPECIAL NOTE: To guard personal safety and avoid damaging
equipment it is important to have a full understanding of electrical
wiring practices and safety. The following sections provide general
guidelines relating to the AAN-1/2, but are not a substitute for complete
training in dealing with electrical systems!
3.1 Power
Power Connection: TB8
Power is supplied to the AAN-1/2 by the voltage connection in terminal block 8 (see Part 2.1 for exact
locations of terminals). The power connection should be 12-24 VDC. Power consumption is 250 mA. The
AAN-1/2 is protected from over-current and over-voltage by onboard circuitry.
Take care when selecting a power supply for use with the AAN-1/2. Most power supplies in the market today
provide good input/output isolation, however those which do not provide isolation (or have high leakage
capacitance), coupled with accidental AC power lines interchange, present serious ground fault problems for
installers. With ground fault, the signal reference between subsystems may be 115 VAc (230 VAc) apart. If
these subsystems are interconnected, the large potential difference will cause equipment damage or
personal injury. Apollo recommends the use of isolated continuous power supplies only. All Apollo supplied
power supply assemblies are transformer isolated for safety and to minimize ground loop problems.
In the case of over-current, solid-state fuses integrated on the AAN-1/2 panel will ‘trip’ to protect the
components of the panel. In many cases, the solid-state fuses will reset automatically when normal current
resumes, however it may be necessary to interrupt the supply of power to allow the fuses to reset.
3.2 Grounding
Special care should be taken when grounding the AAN-1/2 controller and other devices connected to it via
the direct communication lines. Each device must be grounded to provide ESD protection, personnel safety,
and signal reference for devices which communicate with each other. Grounding the reader provides a good
shield against external transients. There are three types of circuit grounds in systems using Apollo products:
DC ground, RS-485 signal ground, and Safety (Earth) ground.
3.2.1 DC Ground
This is typically the minus (-) side of the DC output of the power supply. It is to be connected to the DC
ground input of all devices being powered by one supply. It must not be connected in any way to any of the 5
RS-485 signals or the AC side of the line including Safety (Earth) ground (one connection to Safety (Earth)
ground is acceptable, but this connection is usually internal in the host computer and should not be
introduced externally if direct connection is used (RS-232/485)).
3.2.2 RS-485 Signal Ground (SG)
This is the 5th wire used for the RS-485 communications. It is used to provide a common reference between
all devices on the line and should only be connected to each of the devices' SG input. The SG wire must not
be allowed to touch any other potential, especially earth ground. The shield drain wire of the RS-485
communications cable is commonly used to connect the SG leads together. Usually this wire does not have
an electrical insulator. It is important that the SG wire is thoroughly insulated by the installer at all connection
points. Improper insulation of this conductor may allow accidental shorting to earth ground through conduit or
other metallic components, causing intermittent communications or equipment damage.