Communications: electrical – Systems – Selsyn type
Reexamination Certificate
1998-08-27
2002-05-28
Pope, Daryl (Department: 2736)
Communications: electrical
Systems
Selsyn type
C340S315000, C340S315000, C340S315000, C455S003010, C375S258000
Reexamination Certificate
active
06396391
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of wired communication and control systems, in particular to such systems which provide for simultaneous distribution of power and message information along the network wires in a network having a plurality of sensors, actuators and processing elements.
BACKGROUND OF THE INVENTION
Ethernet-based networks are popular as Local Area Networks (LANs) used for computer and communication networks, and are standardized under IEEE802. The network physical media are usually based on copper conductors, interconnecting between the various units comprising the network. Usually twisted-pair or coaxial cables are used. Terminals constituting Data Terminal Equipment (DTE) are connected to the network via ‘network adapter’ units that are tapped into the media. The adapters (also referred to as ‘nodes, network card etc.) handle the interface between the media comprising the bus and the payload units. In a LAN environment, the network adapters are usually housed within the DTE enclosure, and both the DTE and the adapter are locally powered by a power supply within the DTE enclosure. However, in some control networks, power is distributed centrally via the network so as supply power either to the network adapters only or to both the network adapters and the payloads.
FIG. 1
shows such a network
10
comprising a backbone or bus
11
having power and data lines
12
and
13
, respectively. A dedicated power source
14
is connected across the power lines
12
whilst various adapters
15
,
16
and
17
are connected across both the power and data lines
12
and
13
so as to receive power and allow for bi-directional communication with other adapters via the bus. The adapters
15
,
16
and
17
can be standalone units (‘hub’ units), or housed in the DTE enclosure, as is the case in network cards which are housed within a Personal Computer enclosure. The use of the dedicated power source
14
that provides power to all of the adapters in the network obviates the need to supply power locally to each of the adapters separately.
Payloads
18
,
19
and
20
are connected to the adapters
15
,
16
and
17
respectively. As seen, the payload
18
has both power and data connections to the adapter
18
so as to receive power therefrom and effect bidirectional data communication therewith. The payload
20
is connected directly to the power lines
12
so as to receive power directly therefrom, whilst the payload
19
is powered via a local power supply
21
. It should be noted that in the following description and annexed figures, the terms “power source” and “power supply” are used interchangeably.
U.S. Pat. No. 5,475,687 (Markkula et al.) is representative of a large number of patents describing networks employing the same ‘bus’ network topology for control and automation. Specifically, nodes are used to interface between the network media and the sensors/actuators used as payloads. Similar to the LAN application, the nodes can be integrated into the payload or used as standalone units.
Although control networks can use the same powering scheme as described above, where each payload and its associated node are independently locally powered, other approaches are more popular in order to reduce wiring and powering complexity. The most popular powering method involves carrying the power in the network wires in addition to the data. This is usually performed using one of the following possibilities:
(a) Additional dedicated power wires are used along with the data wires, as shown in FIG.
1
and described in U.S. Pat. No. 5,469,150 (Sitte).
(b) Power and data are transmitted together over the same media, as described in U.S. Pat. Nos. 5,454,008 (Baumann et al.) and 5,148,144 (Sutterlin et al.) In this case, each node contains special circuitry in order to separate the data and power. In addition, means (shown as “Source Coupler” in
FIG. 2
) must be provided to interface the power supply to the bus in order that the low source impedance and power supply noise do not affect the data—transmission in the network.
FIG. 2
shows schematically a network
25
employing so-called “Token Ring” topology, wherein a plurality of nodes is serially connected one to another. In addition, the network conforms to such an arrangement so as to send both power and data along the same wires. The network
25
comprises a bus shown generally as
26
fed by a power source
27
interfaced to the bus
26
by means of a source adapter
28
. The source adapter
28
ensures that the low-source impedance and supply noise do not affect the data communication in the network. Network adapters or nodes
30
,
31
and
32
are serially connected to the bus
26
via discrete bus sections
26
a
,
26
b
,
26
c
and
26
d
so as to receive combined power and data signals therefrom and feed data signals thereto. Payloads
33
,
34
and
35
are connected to the adapters
30
,
31
and
32
respectively. The payloads
33
and
35
have both power and data connections to the respective adapters
30
and
32
so as to receive power therefrom and effect bidirectional data communication therewith. In contrast thereto, the payload
34
is powered via a local power supply
36
. In this case, each node contains special circuitry in order to separate the data and power.
Although the power carried in the bus
26
can be used for both the nodes and the payloads (as shown in payloads
33
and
35
), this imposes a limit either on the power consumption of the payload or on the total length of the wires constituting the network. This limitation is overcome by the combined approach shown in
FIGS. 1 and 2
, wherein the nodes (usually low-power units) are powered from the network, while highly consumption payloads such as
19
and
34
are locally fed.
U.S. Pat. No. 5,095,417 (Hagiwara et al.) describes a control network employing Ring topology wherein nodes are connected in cascade in a manner similar to that shown in FIG.
2
. The two end nodes are likewise cascaded so as to form a complete ring. Similar to the above discussion, separated or combined power/data lines can be used, and nodes/payloads can be powered locally or from the network.
In all types of buses described, regenerators are usually allowed. Regenerators (also referred to as repeaters, routers, bridges etc., according to their complexity and functionality) are used in order to extend the bus length limit. In addition, repeaters can also be used for connecting two distinct, physically separate networks performing different functions. The repeater is usually added as ‘cut and add’, in series with the existing lines. Similar to nodes, repeaters can be fed locally or from the network. The latter is preferred, since there is then no need to route additional wires to the repeater.
As demonstrated above, networks can be categorized as follows:
(a) Wiring topology. Either ‘bus’ topology can be used, as demonstrated in
FIG. 1
, or ‘serially connected’ wiring topology can be used (illustrated in FIG.
2
). Mixed networks can also be implemented. For example, data lines can be serially connected in cascade while the power lines are connected in ‘bus’ topology.
(b) Powering scheme. Three powering schemes can be employed. The first involves the case where the network adapters and the payloads are locally fed. This is usually the case in LAN systems, where line powering is not used. The second scheme involves the case where the nodes are fed from power carrying wires included in the network wiring, as shown in FIG.
1
. The third option refers to the case where the payloads are also fed from the network, either by directly connecting to the network wiring (Payload
20
in
FIG. 1
) or fed via the network adapter (Payload
18
in FIG.
1
). Mixtures of the above schemes can also be implemented, as described in
FIGS. 1 and 2
.
Known network configurations using line powering as described above with reference to
FIGS. 1 and 2
, employ a single power supply only, usually connected at an end of the line, although this is not mandatory. This approa
Pope Daryl
Serconet Ltd.
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