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CAN-USB adaptor

For distances up to 1000 meters

CAN-Key by SMT (US) is a CAN-USB adaptor designed for CAN bus communication. It is used in networks with a large number of nodes that require communication over large distances.

USB power can be used for networks or devices that require less than 400 mA in total (Photo: SMT)

APPLICATIONS SUCH AS BUILDING AND INDUSTRIAL AUTOMATION require reliable and robust communication as well the ability to operate without extra infrastructure such as repeaters and hubs. Lightweight protocols that operate over CAN are suitable for sensor data networks that communicate in infrequent small data packets.

The designed unit is capable of transmission rates as low as 10 kBit/s to 125 kBits/s allowing communication distances up to 1000 m over CAT5 cable. At this communication rate, branches with no terminations are possible, making the CAN network topology for building and industrial applications simplistic and reliable.
Also the product is suitable for application fields like building automation systems,
industrial control data networks, automotive systems, and HVAC controls.

The unit’s CAN bus connects to a RJ45 port allowing usage of CAT5 cabling for long distance communication and usage of standard networking crimp/termination hardware. It also got a port for external power injection since voltage drop due to long cable routes and large number of devices often requires the bus to be powered by a higher voltage.

Network isolation

Wiring between units and to electrical power supplies is a potential entry point for noise that could adversely affect sensitive measurements. In certain cases, the CAN network must be isolated or filtered to prevent noise and/or ground loops and from affecting data-logger measurements. To achieve power isolation, an isolation power transformer can be used. Another grounding point of the CAN bus may occur through the USB port and through the computer used to monitor the network. The computer has to be plugged into the isolation transformer. Noise on CAN power and ground can be filtered by placing capacitors from both CAN power and CAN ground tied to building/earth ground. The size and voltage of capacitors is to be determined by the amount of AC noise recorded on the CAN network.

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