I N T E R FA C E U SES AND A P P L I C AT I O N S
I N T E R FA C E U SES AND A P P L I C AT I O N S
Communications standards are used extensively in applications with a host PLC or with a computer in a network where one or more interfaces are used. Sometimes a PLC with an RS-232C or RS-422 communication interface must communicate with an RS-485 device. In this case, an RS-232C–to– RS-485 converter (or an RS-422–to–RS-485 converter) can provide this communication (see Figure 8-49). These converters provide electrical isola- tion, in addition to longer distance. Figure 8-50a illustrates one of B&R Industrial Automation’s interface converters, which can be used for com- municating between two PLCs (see Figure 8-50b) over a long distance (maximum of 500 m, or 16,500 ft). Each PLC starts its interfacing via RS- 232 (or RS-422) and transfers to RS-485 to achieve the required distance.
RS-232C
RS-232–to–RS-485
RS-422–to–RS-485
Figure 8-49. (a) RS-232C–to–RS-485 and (b) RS-422–to–RS-485 converters.
Industrial Text & Video Company 1-800-752-8398
www.industrialtext.com
S ECTION Components Special Function I/O and C HAPTER 2 and Systems
Serial Communication Interfacing 8
2 3 Installation/Grounding (DIN rail mount)
1–DIN rail (grounded)
2–RS-232 cable 3–Cable holder 4–Cable shield 5–Grounding clamp 6–Voltage supply cable 7–Cable holder
8–RS-485 cable
(e.g., twisted pair) 9–Grounding the 6 7 8 negative supply
(a)
RS-232C or RS-422
RS-232C or RS-422
Interface
Interface
RS-232C or RS-422
RS-485 to
to RS-485
RS-232C or RS-422
(16,500 ft) 5000 m Max
(b)
Figure 8-50. (a) B&R Industrial Automation’s interface converter and (b) an example of the convertor communicating between two PLCs.
Figure 8-51 shows the relationship between transmission distance and data rate for the RS-485 interface converter. This diagram is based on a cable with an impedance of 110 Ω , a capacitance of 41 picofarads/m, and a cable
ohmic resistance of 0.094 Ω /m. The converter is capable of driving a signal at rates of 115.2K baud at a distance of 1500 m (5000 ft). It is also capable of operating at a distance of 5000 m (16,500 ft) at a rate of 9.6K baud.
Figure 8-52 shows another application of serial communication. In this example, an isolated link coupler (1747-AIC) interface connects several Allen-Bradley SLC-500 PLC processors to a DH-485 network (RS-485– based). This link coupler provides a connection for each of the SLC-500
Industrial Text & Video Company 1-800-752-8398
www.industrialtext.com
S ECTION Components Special Function I/O and C HAPTER 2 and Systems
Serial Communication Interfacing 8
Baud Rate (Kbits/sec) 38.4 30
Distance (m)
Figure 8-51. Baud rates for transmission distances in a RS-485 converter.
CPUs in the DH-485 network. The DH-485 network also interfaces with a personal computer through an RS-232–to–DH-485 communication inter- face. The maximum length of the main trunk of the DH-485 network is 4000 feet at a rate of 19.2K baud. This type of subnetwork is very useful for remote programming and data acquisition links of up to 32 devices.
RS-232/DH-485 Interface Connector
DH-485 network SLC 500
SLC 500
SLC 500
1747-AIC Isolated Link Coupler
Figure 8-52. PLC processors connected to an isolated link coupler interface.
Industrial Text & Video Company 1-800-752-8398
www.industrialtext.com
S ECTION Components Special Function I/O and C HAPTER 2 and Systems
Serial Communication Interfacing 8
K EY ASCII I/O interfaces T ERMS BASIC module
cold junction compensation direct action I/O interface distributed I/O processing encoder/counter module fast-input interface fast-response interface fuzzy logic interface intelligent I/O interface lead resistance compensation network interface module proportional-integral-derivative (PID) interface resistance temperature detector (RTD) interface serial communication servo motor interface stepper motor interface thermocouple input module weight input module wire input fault module
Industrial Text & Video Company 1-800-752-8398
www.industrialtext.com
Parts
» An Industrial Text Company Publication Atlanta • Georgia • USA
» C HAPTER T HREE L OGI C C ON CEPT S
» 3 -3 P RINCIPLES OF B OOLEAN A LGEBRA AND L OGIC
» 3 -4 PLC C I RCU I T S AN D L OGI C C ON TACT S Y M BOLOGY
» C ONTACT S YMBOLS U SED IN PLC S
» L OADING C O N S I D E R AT I O N S
» M E M O RY C A PA C I T Y AND U T I L I Z AT I O N
» A P P L I C AT I O N M E M O RY
» D AT A T ABLE O R G A N I Z AT I O N
» 6 -2 I /O R ACK E NCLOSURES AND T ABLE M APPING
» I /O R ACK AND T ABLE M APPING E XAMPLE
» 6 -4 P L C I NSTRUCTIONS FOR D ISCRETE I NPUTS
» 6 -6 P L C I NSTRUCTIONS F OR D ISCRETE O UTPUTS
» 7 -3 A NALOG I NPUT D ATA R E P R E S E N TAT I O N
» 7 -4 A NALOG I NPUT D ATA H ANDLING
» 7 -6 O V E RV I E W OF A NALOG O UTPUT S IGNALS
» 7 -8 A NALOG O UTPUT D ATA R E P R E S E N TAT I O N
» 7 -9 A NALOG O UTPUT D ATA H ANDLING
» C HAPTER E IGHT S PECI AL F U N CT I ON I /O AN D S ERI AL C OM M U N I CAT I ON I N T ERFACI N G
» T HERMOCOUPLE I NPUT M ODULES
» E NCODER /C OUNTER I N T E R FA C E S
» S TEPPER M OTOR I N T E R FA C E S
» S ERVO M OTOR I N T E R FA C E S
» N ETWORK I N T E R FA C E M ODULES
» S ERIAL C O M M U N I C AT I O N
» I N T E R FA C E U SES AND A P P L I C AT I O N S
» 9 -3 L ADDER D IAGRAM F O R M AT
» 9 -5 L ADDER R E L AY P ROGRAMMING L ADDER S CAN E V A L U AT I O N
» P ROGRAMMING N O R M A L LY C LOSED I NPUTS
» 9 -1 0 A RITHMETIC I NSTRUCTIONS
» 9 -1 4 N ETWORK C O M M U N I C AT I O N I NSTRUCTIONS
» L ANGUAGES AND I NSTRUCTIONS
» F UNCTION B LOCK D IAGRAM (FBD)
» S EQUENTIAL F UNCTION C H A RT S (SFC)
» P ROGRAMMING L ANGUAGE N O TAT I O N
» P ROGRAMMING N O R M A L LY C LOSED T RANSITIONS
» D IVERGENCES AND C ONVERGENCES
» -1 C ONTROL T ASK D EFINITION
» C REAT I N G F LOWCH ART S AN D O U T PU T S EQU EN CES
» C ONFIGURING THE PLC S YSTEM
» S PECIAL I NPUT D EVICE P ROGRAMMING
» S IMPLE S TA R T /S TOP M OTOR C IRCUIT
» F O RWA R D /R EVERSE M OTOR I NTERLOCKING
» AC M OTOR D RIVE I N T E R FA C E
» L ARGE R E L AY S YSTEM M O D E R N I Z AT I O N
» A NALOG I NPUT C OMPARISON AND D ATA L INEARIZATION
» A NALOG P OSITION R EADING F ROM AN LV D T
» L INEAR I N T E R P O L AT I O N OF N ONLINEAR I NPUTS
» L ARGE B AT C H I N G C ONTROL A P P L I C AT I O N
» -7 S H O RT P ROGRAMMING E XAMPLES
» -1 B ASIC M EASUREMENT C ONCEPTS D ATA I N T E R P R E TAT I O N
» I NTERPRETING C OMBINED E RRORS
» B RIDGE C IRCUIT T ECHNIQUES
» R ESISTANCE T E M P E R AT U R E D ETECTORS ( RT D S )
» -1 P ROCESS C ONTROL B ASICS
» I N T E R P R E TAT I O N OF E RROR
» T RAN SFER F U N CT I ON S AN D T RAN SI EN T R ESPON SES
» D E R I V AT I V E L APLACE T RANSFORMS
» Out () s = ( )( ) In () s Hp () s
» S ECOND -O RDER L AG R ESPONSES
» D IRECT -A CTING C ONTROLLERS
» T WO -P OSITION D ISCRETE C ONTROLLERS
» T HREE -P OSITION D ISCRETE C ONTROLLERS
» -5 P R O P O RT I O N A L C ONTROLLERS (P M ODE )
» PV () s ( 1 + Hc Hp () s () s ) = SP Hc Hp () s () s () s
» CV () t = K I ∫ 0 Edt + CV ( t = 0 )
» CV ( t = 2 ) = K I 0 Edt + ∫ CV ( t = 1 )
» -7 P R O P O RT I O N A L -I NTEGRAL C ONTROLLERS (PI M ODE )
» -8 D E R I VAT I V E C ONTROLLERS (D M ODE ) S TANDARD D E R I V AT I V E C ONTROLLERS
» -9 P R O P O RT I O N A L -D E R I VAT I V E C ONTROLLERS (PD M ODE )
» -1 2 C ONTROLLER L OOP T UNING
» Z IEGLER –N ICHOLS O PEN -L OOP T UNING M ETHOD
» I TA E O PEN -L OOP T UNING M ETHOD
» S O F T WA R E T UNING M ETHODS
» R ULE -B ASED K NOWLEDGE R E P R E S E N T AT I O N
» S T AT I S T I C A L AND P ROBABILITY A N A LY S I S
» -1 I NTRODUCTION TO F UZZY L OGIC
» -2 H I S T O RY OF F UZZY L OGIC
» -3 F UZZY L OGIC O P E R AT I O N
» F U Z Z I F I C AT I O N C OMPONENTS
» F UZZY P ROCESSING C OMPONENTS
» D E F U Z Z I F I C AT I O N C OMPONENTS
» S YSTEM D ESCRIPTION AND O P E R AT I O N
» M EMBERSHIP F UNCTIONS AND R ULE C R E AT I O N
» IF A = PS AND B = NS THEN C = ZR IF A = PS AND B = NS THEN D = NS
» C HAPTER N INETEEN I /O B US N ET WORK S
» -4 D EVICE B US N ETWORKS B YTE -W IDE D EVICE B US N ETWORKS
» B IT -W IDE D EVICE B US N ETWORKS
» F IELDBUS P ROCESS B US N ETWORK
» P ROFIBUS P ROCESS B US N ETWORK
» I /O B US N ETWORK A DDRESSING
» P ANEL E NCLOSURES AND S YSTEM C OMPONENTS
» -3 N OISE , H E AT , AND V O LTA G E R EQUIREMENTS
» T ROUBLESHOOTING PLC I NPUTS
» -2 P L C S IZES AND S COPES OF A P P L I C AT I O N S
» I NPUT /O UTPUT C O N S I D E R AT I O N S
» C ONTROL S YSTEM O R G A N I Z AT I O N
» E Q U I VA L E N T L ADDER /L OGIC D IAGRAMS
Show more