Bray 70 Series SERVO PRO DeviceNET - Manual (Page 12)

S70 DeviceNet Servo Installation & Maintenance Manual
2000 BRAY CONTROLS Page 11 of 24
DeviceNet should be grounded at ONE location. Grounding at more then one location may
produce ground loops, while not grounding the network will increase sensitivity to ESD and
outside noise sources. The single grounding location should be at a power tap. Sealed
DeviceNet power taps are designed to accommodate grounding. Grounding near the physical
center of the network is also desired.
The trunk drain/shield should be attached to the power supply ground or V- with a copper
conductor that is either solid, stranded, or braided. Use a 1” copper braid or a #8 AWG wire that
is less than 3 meters/10 feet in length. This should then be attached to a good earth or building
ground (such as an 8 foot stake driven into the ground, attached to building iron or to the cold
water plumbing).
If the network is already grounded, do NOT connect the grounding terminal of the tap or ground
of the supply to earth. If more than one supply is on the network, then connect the drain
wire/shield at ONE supply only, preferably near the physical center of the network.
3.1.3 Network Power
In addition to providing communications, DeviceNet also provides power. Because power and
signal conductors both are contained in the cable, devices can draw power directly from the
network without the need for separate power sources.
DeviceNet has a single supply current capability of up to 16 amps using a thick cable trunk line,
and up to 6 amps using a thin cable trunk line , which makes the network highly functional and
cost-effective.
The power bus capabilities for DeviceNet are:
Cable length as long as 500 m (1,640 feet)
Support for as many as 64 nodes of varying current
Adjustable configuration
Because of the flexibility of DeviceNet , there are several power design choices. This section
provides guidelines to help configure power along a network in a way that maximizes
performance and minimizes cost.
Power configuration is adjustable based on your system requirements. The DeviceNet power
bus is supplied by a nominal 24 volt source and can support up to 8 amps on any section of
thick cable trunk line or up to 3 amps on any section of thin cable trunk line. Since this much
current can be drawn from each side of a power tap, a single supply network can possibly
provide twice these current levels. If the system has even greater requirements, DeviceNet
can support multiple power supplies, which can result in almost unlimited power. The majority
of DeviceNet applications, however, will require only one power supply.
Important: Before you begin, familiarize yourself with the country and local codes in which the
system to be installed. In the U.S. and Canada the DeviceNet cable system must be installed