RTS ROAMEO User manual

APPLICATION NOTES:
PoE for ROAMEO Access Points
ROAMEO is a wireless matrix system from RTS. In this Application Note, we will look at a way of connecting the
ROAMEO Access Points using Power over Ethernet, PoE.
Power over Ethernet is a way of simplifying wiring for devices that connect to Ethernet. With PoE, there is no
need for a separate power supply. There is an upper limit on the amount of power that can be supplied using
PoE, and the limit is dependent on the type of PoE switch used. In general, PoE is intended for devices that
require little power, up to about 13 Watts. (There is another standard called PoE Plus, which allows up to 25
Watts of power, but we will not get into that here.) With PoE, the data signal is superimposed on the power.
On the receiving end, filters are used to pick out the data from the power. When a PoE device is turned on, it
communicates with the PoE switch to “negotiate” the right electrical parameters. For this reason, PoE devices
can never be connected in cascade.
The ROAMEO Access Point, AP-1800, is designed to
be tolerant to PoE, but it is not designed to use PoE
directly. Expressed differently, it is PoE tolerant but
not PoE enabled. RTS does supply a PoE adapter kit, to
allow the AP-1800 to work with a PoE enabled switch.
The PoE kit is shown in Figure 1.
The PoE adapter is designed to support three different
voltages. The AP-1800 expects 12 V. The setting on the
PoE adapter (TP-Link) must be set to 12 V before it is
connected to the Access Point. This is shown in Figure
2. To set it to 12 V, slide the little selector to the left.
Note if the selector is in the wrong position, nothing will
break. The AP simply will not power up.
The kit can be ordered as any other part. The part
number is F.01U.335.167 (POE ADAPTER 12V) and it
contains the following parts:
• The PoE adapter
• A barrel adapter
• A short DC-cable
• Two Ethernet-cables Figure 1. The PoE kit for AP-1800
INTRODUCTION
Figure 2. The voltage selector should
be in the left-most position for 12V
SETTING THE VOLTAGE ON THE PoE ADAPTER
WHAT IS PoE?
THE ROAMEO AP

Figure 4. This is the symbol for a PoE-enabled AP-1800
Figure 5. Connecting a single
PoE-enabled AP-1800
Figure 6. Connecting another AP
to a PoE-enabled AP
HOW TO CONNECT THE PoE ADAPTER
SYSTEM DIAGRAMS
CONCLUDING REMARKS
In the first example, we will show how a single AP-1800 may be connected. Note the PoE-enabled AP-1800 on
the right is connected directly to the switch. The other two APs are running on local power (meaning they are
connected to power using the supplied AC to DC converter). The first AP is connected to PoE, but is not
utilizing that power.
In the second example, another AP is connected to the PoE-enabled AP. The second AP must have local power.
The OMNEO signal coming out of the second Ethernet jack on the PoE-enabled AP no longer has power.
ROAMEO Access Points can work with PoE, but they require an adapter, which must be purchased separately
(e.g., it is not included). Each AP that requires PoE must be connected directly to a PoE switch. The total power
of all PoE enabled APs must not exceed the total power of the PoE switch.
We will now look at some ways in which the PoE-enabled Access Point can be connected to the system. To
symbolize a PoE-enabled Access Point, we will use the symbol shown in Figure 4.
Figure 3. How to connect the PoE adapter
Once the voltage has been set to 12 V as described in the previous section, the cable from the PoE switch is
connected to the rear of the PoE adapter, and the signal output and DC connectors are connected to the AP-
1800. Note you must use the barrel adapter to make a reliable electrical connection between the cable and the
AP-1800. Without the barrel connector, it will not work.