HVAC Control in the New Millennium.pdf - HVAC.Amickracing

Computer Networks and SecurityGateway AccessMasters that behave as a slave in a field-bus network act as couplersor gateways. These AS-i gateways provide access to sensor andactuator data from all layers of the automation architecture. AS-i gatewaysare available for Profibus, Interbus, DeviceNet, CAN, SDS,MODBUS, MODBUS+ and RS-232/-422/-485. Stand-alone masters actas controllers for simple tasks.An As-i power supply unit serves as the power supply for theslaves. It forms the voltage pulses for data transmission and can beconnected to the network at any point. It feeds a symmetrical supplyvoltage of 30 VDC into the cable. Power supplies are available withratings of 2.2 to 8-A.AS-i CableThe standard AS-i cable is 2-core, 2 by 1.5-mm, rubber insulated,with a special profile that prevents reversal of the poles when connectingdevices. The electrical connection is made by penetration contacts,which pierce the rubber insulation to make a connection to the two cablewires. This connection method eliminates stripping and terminating.If a device needs to be moved to another location on the cable, itis easily done. The cable is self-healing and holes made in the cableduring installation close when the connection is removed.Cables are available for applications that require data and powerseparately. A black cable is used for supply voltages up to 30-V and a redversion for supply voltages up to 230-VAC. Table 8-1 lists the AS-i cablecharacteristics.Table 8-1. AS-i Cable Characteristics————————————————————————————————Trapezoidal mechanically coded cableReverse voltage protectionOil-resistant versionsUL recommendedData and power, yellow version - 30 VDCPower - 24 VDC (black) to 230 (red) VACPiercing connectors————————————————————————————————©2001 by The Fairmont Press, Inc. All rights reserved.