Devicenet scanner module, available from Balmoral Technologies , allows easy communication between various devices on the industrial network including LED displays, PLCs and HMI.
Messaging support allows editing device parameters from within the PLC programme. Cyclic data support allows the user to define data refresh rates, which is suitable for manufacturing applications. Change-of-state data support is suitable for high-speed applications, where throughput and node prioritisation is important. With change-of-state operation, there is no output of information from an actuator/sensor unless something has changed. This frees the network from ‘housekeeping’ duties.
DeviceNet bus addressing can be conducted in the following different modes:
- Peer-to-Peer with multi-cast networks are generally token-pass networks. Each device can send messages only when it has the token. The token gets passed based on the node number (round robin) or possibly through a user-defined priority list. There is no sense of mastership or priority and it is not deterministic. The Multi-Cast feature allows one-to-many and many-to one relationship to be built dynamically.
- Multi-Master with multi-cast: This is where more than one unit acts as a master.
- Master/Slave special case: This is ‘polled’ or ‘change-of-state’ (exception-based). Rather than a Master going through a polling list (scanning), DeviceNet sensors/actuators report data (input or output) on a change-of-state (COS) basis as the events occur. This method is considered more efficient for discrete applications.
The DeviceNet scanner communicates with the Modicon TSX Quantum PLC processor through discrete and block transfers over the backplane. A DeviceNet product may behave as a client, server, or both. The scanner communicates with the scanned devices through strobe, polled, change-of-state, and cyclic messages. It uses these messages to solicit data from or to deliver data to each device on the network.
Data received from the devices or input data is organised by the scanner and made available to the PLC processor. Data received from the PLC processor or output data is organised in the scanner and sent on to the network devices, in the following steps:
- Strobed: Multi-cast message starts the scan cycle. Strobable slaves respond, based on their latency.
- Polled: The Master interrogates each sensor/actuator according to the ‘polling list’. Polls are sent out even as strobe responses are being received, as bandwidth allows.
- Cyclic: Devices report data on a user-configured, time-increment basis (input or output). Cyclic data production is considered more efficient for applications with slowly changing analogue I/O.
- COS: A device reports its data only when there is a change. This is considered more efficient since only data changes are transmitted. It can be used along with Poll or Strobe.
Specifications for DeviceNet Parameters:
- Communication Rates: Strobe, poll, COS (Change-of-State), or 125 kbps, 250 kbps, 500 kbps
- Cyclic I/O data for each node Messaging Capabilities: Interscan delay (Master) Poll, Strobe, COS, or Cyclic, Scan list
- Background poll rate
- Optical isolation between backplane
- PLC Processor-to-Scanner Communication: Network DIP Switch Selectable
- 8 I/O: uses 8 Input and 8 Output registers
- 32 I/O: uses 32 Input and 32 Output registers Any I/O slot in Quantum PLC rack, local, remote, or DIO DeviceNet Data
- 8 I/O Configuration: up to 28 words of input
- Network address and output from the network: 32 I/O Configuration: up to 124 words of 00-63 input and output from the network
- Power Consumption: operating temperature
- DeviceNet current load: 32°F to 140°F (0°C to 60°C) 90mA (maximum)
- Storage temperature backplane current load: -40°F to + 185°F (-40°C to +85°C) 400mA at 5V DC (maximum)
- Humidity 5 to 95% non condensing
- DeviceNet power: shock (unpacked): 24V DC, nominal operating 30g, Non operating 50g vibration (unpacked)5g from 10Hz to 500Hz
AVG Automation’s DeviceNet Scanner lets the user to connect a wide variety of industrial devices, such as limit switches, photoelectric sensors, proximity sensors, valve manifolds, motor starters, process sensors, bar code readers, variable-frequency drives, panel displays, and operator interfaces from over 150 manufacturers world-wide, directly to the Modicon TSX Quantum PLC.
The DeviceNet Scanner knows what is connected and where. Each component on the DeviceNet has its own unique address that cannot be used by any other on the network. All communications occurs on a single DeviceNet cable. Instead of the discrete wiring from your PLC to each sensor or actuator in your application, with DeviceNet, adding or removing a component is simple. Users can just ‘tee off’ from the cable wherever they need to install a sensor or actuator, drop a line and let it run. This all adds up to lower wiring costs and a quicker installation.