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DeviceNet™ Troubleshooting

1. Add a second power supply Break the network into two separate networks 1 800 544 7769 Fax 763 553 0708 TURCK Minneapolis MN 55441 11 CANH CANL Voltage Test Each node contains a CAN transceiver that generates differential signals onto the data conductors When the network communication is idle the CANH and CANL voltages are approximately 2 5 volts Faulty transceivers can cause the idle voltages to vary and disrupt network communication Although this test indicates that faulty transceivers may exist on a network it will not indicate which node has the faulty transceiver If a node with a faulty transceiver is found perform the CAN Transceiver Resistance Test Turn all network power supplies on Configure all nodes for their maximum current draw from network power Turn on outputs that use network power Measure and record DC voltage between V and V where each power supply connects to the trunk 4 Measure and record DC voltage between V and V at the ends of the network lt 2 0 Volts CANH CANL conductor has intermittent short to shield or V Check all open style and field wireable connectors Check CANH and CANL conductors for continuity Possible faulty transceiver on one or mode nodes refer to CAN Transceiver gt 3 0 Volts CANH CANL conductor has intermittent short to V Network in bus off state error 91 Check all open style and field wireable connectors Check for excessive common mode volt
2. Network PS SS kuiniluiuininimimikusi 4 a A gt 10 www turck com 1 800 544 7769 Fax 763 553 0708 TURCK Minneapolis MN 55441 Power Common Mode Voltage Test www turck com When the current is drawn through the power pair on the DeviceNet trunk line the resistance of the power pair conductors produces the common mode voltage drop The effect of the common mode voltage is that the V line decreases from the 24 VDC at the power supply as you move farther from the power supply More significantly the V line increases from the 0 VDC value at the power supply along the length of the trunk line This test assumes that V decreases and V increases are equal Since CANH and CANL both are referenced to the V wire if the voltage on the V line varies more than 4 65 VDC at any two points the CAN transceivers will fail to operate properly Turn all network power supplies on Configure all nodes for their maximum current draw from network power Turn on outputs that use network power Measure and record DC voltage between V and V where each power supply connects to the trunk Measure and record DC voltage between V and V at the ends of the network gt 9 3 Volts Network will not operate properly Possible solutions Shorten overall length of the network cable Move power supply in direction of overloaded section Move nodes from overloaded section to less loaded section Move high current loads close to the power supply
3. 2 ft 250 m 820 ft 250 m 820 ft 6 m 20 ft 78 m 256 ft 500 kb 100 m 328 ft 100 m 328 ft 6 m 20 ft 39 m 128 ft The length of the network is the sum of the trunk length and cumulative drop length Thick Cable Capacity The power distribution chart Figure 1 shows the maximum allowed current through the power conductors of the thick cable Distance is measured from a single 24 VDC power source If the maximum current exceeds the specified value at any given point on the network the power supply systems should be re designed Figure 1 provides thick cable current ratings Figure 1 Current available through power conductors of thick cable 8 00 Maximum Current Capability amps 0 50 100 150 200 250 300 350 400 450 500 164 328 492 656 820 1984 1148 1312 1476 1640 Length of Network in meters feet Thin Cable and Cable 1 The maximum cable length used in trunk drop topology based on the data rate is Table V Thin Cable and Cable Topology 125 kb 100 m 328 ft 100 m 328 ft 6 m 20 ft www turck com 1 800 544 7769 Fax 763 553 0708 TURCK Minneapolis MN 55441 Thin Cable Capacity Power distribution chart Figure 2 Figure 1 Current available through power conductors of thick cable shows the maximum allowed current 3 00 through the power conductors ofthe 3 TNIIT 2 thin cable The distance is measured from a single 24 VDC power source A oso E 0 Ba 01 02 03 0
4. 4 06 50 07 of the network the power supply system should be re designed Figure 2 provides thin cable current ratings If the maximum current exceeds the 09 80 0 100 specified value at any given point 33 66 98 131 164 197 230 262 295 328 Maximum Current Capability amps Length of Network in meters feet Flat Cable The maximum flat cable length used in trunk topology based on the data rate is Table VI Flat Cable Topology 420 m 1378 ft 6 m 20 ft 156 m 512 ft 100 m 328 ft 6 m 20 ft 39 m 128 ft Flat Cable Capacity Figure 3 Current available through power conductors of flat cable Maximum Current Capability amps 0 12 52 55 0 100 150 200 250 300 350 400 420 41 82 164 328 492 656 820 984 1148 1312 1378 Length of Network in meters feet www turck com 1 800 544 7769 Fax 763 553 0708 TURCK Minneapolis MN 55441 OUICK START Know the Network Layout An essential part of the troubleshooting process is knowing the layout of the network Survey the network to determine the location or existence of these components Network Topology The trunk cable connects nodes and taps Look for a terminating resistor at each end The drop lines are the non terminated cables that connect nodes to the trunk Location of Nodes Count the nodes and note their location on the network Location of Power Supplies There may be more than one power supply
5. Industr A DeviceNet gg Troubleshooting FIELD GUIDE G1001 Publised 11 11 2013 SCOPE he purpose of this troubleshooting guide is to direct qualified service personnel to the causes of network problems and provide remedies The primary goal of troubleshooting is to minimize network downtime Test procedures described in this Troubleshooting Guide require the use of test equipment to measure voltage current and resistance of the physical media layer It is usually sufficient to have a true RSM multimeter such as Fluke 87 3 Digital Multimeter or similar to run tests and obtain reliable measurements For information on designing DeviceNet systems refer to ODVA publication 27 DeviceNet Planning and Installation Manual 1 1 Network Components DeviceNet uses a trunk line and drop line topology to connect nodes for communication Here is an example Trunk Line JNODE C Trunk Line TR Terminating Resistor Trunk Line The network cable between terminators It is usually a thick cable Drop Line The network cable between the trunk and nodes Each drop line may be no longer than 6 meters 20 feet Tap A branching point from the trunk line There may be one node on a drop line as with a tee tap or multiple drop lines as with a multiport junction box Terminating Resistor The 121 Ohm resistor that is connected to the end of the Trunk Line There are two terminators per network Node An addressab
6. age refer to Power Common Mode Voltage Test CANH 2 0 3 6 CANL 2 0 3 6 CANH CANL 0 45 maximum CANH 2 75 5 1 CANL 0 5 2 86 CANH CANL 0 95 minimum 12 www turck com 1 800 544 7769 Fax 763 553 0708 TURCK Minneapolis MN 55441 CAN Transceiver Resistance Test The CAN transceivers used in DeviceNet nodes have one circuit that controls CANH and another circuit that controls CANL Experience shows that electrical damage to one or both circuits may increase the leakage current in these circuits This test uses an ohm meter to measure the current leakage through the CAN circuits Note The reference values listed below are derived from tests with Philips Model PCA82C251 CAN transceivers and Fluke multimeter Models 77 and 87 Other combinations of transceivers and multimeters may yield different results Disconnect the node from the network Leave the node unpowered Measure and record the DC resistance between CANH and V Measure and record the DC resistance between CANH and V Measure and record the DC resistance between CANL and V 5 Measure and record the DC resistance between CANL and V 4M 6MOhms ESD Discharge Test The following test shows if power and communication lines are affected by an electrostatic discharge ESD may cause damage to the nodes and disrupt network communication Every node is affected by discharge and in the long run most components will deteriorate thus reducing network pe
7. ication1 as Round Cables Thick Cable or Cable II Thin Cable or Cable Flat Cables Table III Cable Specifications provides data for each cable type listed in the DeviceNet Specification 19 strands min CAN L Light Blue impedance 9 9 12oohm 4 10 MHZ DCR at 20 degrees C max 6 9 Ohms 6 9 Ohms 6 9 Ohms 28 Ohms 4 9 Ohms 1000 ft 1000 ft 1000 ft 1000 ft 1000 ft Tape Shield 2 mil 1 mil 1 mil 1 mil 2 mil 1 mil 1 mil 1 mil N A Al Mylar Al Mylar Al Mylar Al Mylar Min Conductor Size 160 Insulation Diameternominal 0 098 in 0 098 in 0 055 in 0 055 in 0 110 in Color V Red V Black DCR at 20 degrees C 3 6 Ohms 3 6 Ohms 17 5 Ohms 17 5 Ohms 4 9 Ohms 1000 ft 1000 ft 1000 ft 1000 ft 1000 ft Tape Shield 1 mil 1 mil 1 mil 1 mil 1 mil 1 mil 1 mil 1 mil N A Al Mylar Al Mylar Al Mylar Al Mylar Vendor Vendor 20 x d lex Application a x d flex ae 2 i Agency Certification NEC UL Compliant NEC a NEC Maa CL2 CL3 min w local gov t CL2 CL3 min w local gov t CL2 min regulations regulations Overall Shield Braid Braid Tape Tape 36 AWG or 36 AWG or 1 mil 1 mil 1 mil 1 mil 0 12 mm Cu 0 12 mm Cu Al Mylar Al Mylar www turck com 1 800 544 7769 Fax 763 553 0708 TURCK Minneapolis MN 55441 Thick Cable and Cable II The maximum cable length used in trunk drop topology depends on the data rate Table IV Thick Cable and Cable II Topology 500 m 1640ft 500 m 1640 ft 6 m 20ft 156 m 51
8. le device that communicates on the network There may be as many as 64 nodes per network Power Supply The 24 volt DC source that powers network communication There may be multiple power supplies on a network located anywhere on the network www turck com 1 800 544 7769 Fax 763 553 0708 TURCK Minneapolis MN 55441 Wiring and Connector Pin Definitions There are five conductors in DeviceNet cables There are three connector types commonly used on DeviceNet systems 7 8 16 minifast mini M12 eurofast micro and screw terminal open Table shows the connector pin definitions and Table II shows the connector styles Shield Drain Connection to the shields in the cable ve Red Connectiontothebus24VDCsupply Connection to the bus supply common 0 VDC CANH Data connection high differential CANL Data connection low differential DeviceNet Cable Classification Table 1 Pin Definitions 1 Bare Drain 1 Bare Drain 5 Red V 2 Red V 2 Red V 4 White CANH 3 Black V 3 Black V 3 Bare Drain 4 White CANH 4 White CANH 2 Blue CANL 5 Blue CANL 5 Blue CANL 1 Black V Table II Connector Styles Male Connectors 0 8 0 0 0 o Female Connectors www turck com 1 800 544 7769 Fax 763 553 0708 TURCK Minneapolis MN 55441 DeviceNet cables are classified according to DeviceNet Specif
9. ng www turck com 1 800 544 7769 Fax 763 553 0708 TURCK Minneapolis MN 55441 NETWORK TESTS Termination Test Termination is used to match the impedance of a node to the impedance of the transmission line being used When impedances are mismatched the transmitted signal is not completely absorbed by the load and a portion is reflected back into the transmission line If the source transmission line and load impedance are equal these reflections are eliminated This test measures series resistance of DeviceNet data pair conductors and attached terminating resistors 1 Turn all network power supplies off 2 Measure and record DC resistance between CANH and CANL at the middle and end of the network lt 50 Ohms Check for more than two terminating resistors Check for short circuit between CANH and CANL wiring Check nodes for faulty transceivers refer to CAN Transceiver Resistance Test 60 Ohms Normal do nothing 71 121 Ohms Check for open circuits in CANH or CANL wiring Check for one missing terminating resistor Split the network down the middle into two segments Check resistance of each segment should be 121 Ohm since only a single terminating resistor is present on each segment Mark a break point and leave it disconnected At least one segment will show resistance to 121 Ohm Split a bad segment into two sections and add temporarily a terminating resistor to the non terminated
10. on a network located at the end middle or anywhere along the cable Only one of the power supplies must be the grounding point for network power When Things Go Wrong The first question is always What has changed If you have added or replaced nodes changed wiring or configured a scanner start to look for a problem where you were working If you cannot find a problem there you will need to determine if the problem is caused by the physical media a node communication fault or the network power distribution It is sometimes difficult to determine the root problem because there can be more than one network problem In general check for physical media and node configuration problems before network power distribution or isolating node communication faults Symptoms of Physical Media Problems All nodes on a trunk segment or Check all wiring and connectors on on a drop stop communicating the segment between the power then may recover or go bus off supply and the terminating power The network communicates Check the resistance between only when the number of nodes conductors on the bus cable or trunk length is reduced CAN DC resistance and terminating resistor values www turck com 1 800 544 7769 Fax 763 553 0708 TURCK Minneapolis MN 55441 Symptoms of Node Problems Slave node is on line but the Change the slave node address to scanner says it does not exist match scanner s scan list The network communicate
11. powered up or when the device receives a software reset Hardware Address Comm Rate Configuration KA Hardware configuration of node addresses and communication rates is lt C accomplished using DIP switches located under the device cover Switches S7 and S8 adjust the communication rate and switches 51 56 set the node S1 S6 Set Node Add address using binary code Switch S1 is the least significant bit and switch l dud S6 is the most significant bit S7 S8 Set Comm Rate Software Address Comm Rate Configuration gt gt ZB Software configuration of node addresses and communication rates is active WZ NA N A when DIP switches S7 and S8 are ON The node address and communication 125 kbps 250 kbps 500 kbps rates are stored in nonvolatile memory Changes to the node address and communication rate reguire the use of a DeviceNet configuration tool Switches 51 56 are ignored when in software configuration mode Rotary Switches Rotary switches provide a more convenient and reliable way of setting the node address or data rate 14 www turck com 1 800 544 7769 Fax 763 553 0708 TURCK Minneapolis MN 55441 The MSD the Most Significant Digit switch sets a tenth digit and the LSD the Least Significant Digit sets a single digit The valid address range is 0 63 The MSD switch set to the PGM programmable position allows use of node commissioning or software setup of the node address The Data Rate switch when a
12. rformance and reliability A repeated node failure in the same production area indicates that an ESD discharge is above the components ratings Transceiver PCA82C251 is rated for 250 VDC ESD discharge classification B machine model C 100 pF R 0 Ohm Tektronix scope model THS730A 200 Mhz 1 GSs or similar may be used for ESD test Connect Channel 1 to CANH and set voltage reference to 500 V Connect Channel 2 to CANL and set voltage reference to 500 V Set differential signal CANH CANL Set time reference to 200 nsec Set trigger point at CH 1 at 250 V Measure voltage and adjust reference levels as required lt 200 VDC Acceptable ESD discharge gt 200 VDC Control systems must be grounded www turck com 1 800 544 7769 Fax 763 553 0708 TURCK Minneapolis MN 55441 13 11 I i j Pet paene AE ee oe AJ ji if i i i Kk Moat ON ins hie p Ad Apu 3 gt h Tektronix CH1 500 V 200nS P Tel 2 500 200nS SETTING NODE ADDRESS AND COMMUNICATION RATE The methods described below are used on TURCK and DeviceNet products and may be different than other vendors implementations The default node address is 63 and the communication rate is set at 125 kbps kilobits per second The node address and communication rate parameters can be set in hardware or software The factory default is Software Configuration Changes to DIP switch settings take effect the next time the device is
13. s only Check the node s CAN transceiver 3 4 3 5 when the node is removed The node is in the I O timeout state Reset the scanner and network power 3400 0 Symptoms of Network Power Distribution Problems Network power distribution problems often produce sporadic or intermittent network failures Slave node will not go on line Check CANH CANL wiring 3 4 Change the slave node data rate to 4 match the scanner s data rate 3 4 Nodes near the end of the Check the bus voltage at the node and the trunk stop communicating common mode voltage at the ends of the bus after operating normally The scanner or multiple nodes Check common mode voltage and go to the bus off state after power supply shield grounding operating normally The scanner does not detect Check power supply shield grounding 3 2 3 3 properly configured slave nodes and common mode voltage The network communicates only Check the bus voltage at the node and the when the number of nodes or common mode voltage at the ends of the bus the trunk length is reduced Network Failure Network cannot go on line Bus off condition error 91 The network communicates only Check bus voltage at node and common 3 3 3 4 when the number of nodes or mode voltage at ends of bus the trunk length is reduced Check each node for Data Rate setting 3 2 3 3 Check each node for CAN transceiver failure 3 2 3 3 Check open style and field wireable 3 2 connectors for proper wiri
14. section Mark the location of the break point and temporary terminating resistor Check the resistance of each section should be 121 Ohm Continue splitting the network until the problem is located and repaired Remove all temporary resistors and bring network back to original state Verify once again that the assembled network has 60 Ohm resistance The same procedure is used to locate connector shorts or faulty transceivers www turck com 1 800 544 7769 Fax 763 553 0708 TURCK Minneapolis MN 55441 Power Supply Ground Test The shield and V of the DeviceNet cable system must be grounded at a single location as shown in Figure 4 preferably near the physical center of the network If multiple power supplies are present ground only at the power supply closest to the middle of the network This test will indicate if multiple grounds are connected Turn off all network power supplies Disconnect V and Shield wires are from earth ground and from each other Measure and record the DC resistance between Shield and earth ground at the far most ends of the network Connect the V and Shield wires to earth ground Check for additional grounded V or Shield wires Normal Range Grounding wire could be up to 10 ft long Grounding is done with e 1 copper braid or 8 AWG copper wire up to 10 ft long Figure 4 Network Grounding Power Tap SHIELD DRAIN Power Supply Cable 15AWG GND V V
15. vailable is used for the selection of a pre defined communication speed In Auto position the node detects the Data Rate through Autobaud It usually takes several poll messages to be transmitted for the node to lock in the appropriate Data Rate In addition to these four predefined positions the Data Rate switch can be set to PGM programmable mode The PGM position is any nonpredefined position Changes to the rotary switch settings take effect the next time the device is powered up or when the device receives a software reset www turck com 1 800 544 7769 Fax 763 553 0708 TURCK Minneapolis MN 55441 15

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