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1. EC D485ic Users MANUAL ISOLATED RS 232 To RS 485 CONVERTER FOR 2 AND 4 wiRE RS 485 wiTH G ROUND WIRE 1 INTRODUCTION RS 485 has become one of the most common data communication standards in open multi vendor automation projects More robust than RS 232 and more flexible than RS 422 it allows a single master device to communicate with mul tiple slave devices 1 1 Product Over view For robust operation the ECD485ic is an essen tial component of your industnal applications It provides the following unique combination of features Safely converts between EIA standard RS 232 and RS 485 signals Isolates and protects the data signals and power supply grounds With floating grounds RS 232 cable runs up to 50m can be guaranteed with quality low capacitance cable like Beldon 1422A at 42pF m RS 232 requires lt 2500pF per Signal wire Over 2500v optical isolation between RS 232 and RS485 5kv test isolation and 2500v galvanic isolation between RS485 and the power supply 3kv test Isolation The full isolation 3 port model also has isola tion between RS 232 and powersupply For rapid troubleshooting LED indicators for the TX RX and power status Wide power supply range 9 to 36vdc with spike protection allows use with 9v 12v 15v 24v power supplies or direct from 12v or 24v battery systems EC D485ic User Manual EC DATA TECHNOLOGIES PTE LTD specialist in Electronics amp Data Commu2. Note it fits best on the DIN 50022 style dh rail 1 Block 208 Hougang Street 21 04 213 Singapore 530208 Tel 65 62843373 Fax 65 62857737 a a A EN 50 022 7 5mm EN 50 035 EN 50 022 15mm EC D485ic User Manual www ecdata tech com Zz 6 of 6
3. 000m per EIA 485 500m per ISO 8482 Practical maximum Bus Length 3000m with high quality cable and other con ditions Maximum Speed At least 115Kbps 5 2 Isolation 5 2 1 Daa 92a 5 2 4 5 2 5 Power Supply between input supply and data signals full galvanic isolation 3kV test voltage Power Supply between input supply and data signals full galvanic isolation 3kV test voltage Data between RS 485 port A and port B optical isolation 5kV test voltage Encapsulant if ordered 14 000v per mm Overall rating at least 2500v 5 3 Power Supply Dale 5 3 2 5v Model Supply of 4 75v to 5 25v 175mA average 9 36v Model 1 2watt at 24vdc about 50mA www ec data tech com 5 of 6 EC DATA TECHNOLOGIES PTE LTD specialist in Electronics amp Data Communication 5 4 Environmental 5 4 1 Ambient operating temperature OC to 60C 5 4 2 Ambient storage temperature 40C to 100C 5 4 3 Relative Humidity 10 to 95 RH non condensing 5 4 4 Casing fungus and termite resistance Good 5 4 5 Casing flame characten stics self extinguishing 5 5 Mechanical Dimensions a 93 3 5 5 1 Height Width Depth See drawing oo oo i i pel 5 5 2 Weight 1309 T 5 5 3 Terminal Capacity 2 5mm strand 12 AWG apa 4 0mm solid 12 AWG Onin MOL 5 5 4 Mounting Rail Ta DIN EN 50022 35mm symetnc al DIN EN 50025 32mm asymetnc al
4. ble on pins 2 3 5 and 1 2 3 4 5 respectively The diagram above shows how to wnite a cable between 2 units of ECD485ic To facilitate mak ing multi drop cables each signal but ground is available on 2 pins Pin 1 R is also on pin 6 pin 2 T Is also on pin 7 pin 3 T Is also on pin 8 and pin 4 R isalso on Pin 9 It is also critical that the Signal Ground be propery connected you void your wanantee if you do not connect this ground propery If your RS 485 bus does not have the 3 ground wire then you should at least connect the Sig nal Ground Gnd A or SG of RS485 to the nearest device s digital ground 4 4 Placing your bus terminators 485ic 01 _ Pin 1 Ov D E SN75176B EO Gnd a 5v e s e Jumpers gt C ale MA X232EPE yy Jumper location Each RS 485 segment requires a 120 ohm ter minating resister at each end assuming your www ec data tech com 4of6 EC DATA TECHNOLOGIES PTE LTD specialist in Electronics amp Data Communication cable has a charactenstic impedance of 120 ohms T Bias T Term T Bias R Bias R Term R Bias 2 Wire 4 Wire BARBER Detail of jumpers 4 5 Planning the panel wiring Power Supply The ECD485ic 9 to 36vdc Is fully protected from reverse winng and will sustain no damage The ECD485ic 5vdc 5 model is partially protected and if a fuse is installed in the V supply wire shoul
5. d not sustain any damage RS 485 Fuses RS 485 field wires should be protected by 250mA fuses RS 485 interface ICs are intemally protected from short circuits These fuses protect the system from over voltages caused by mis winng for example winng 110vac to the bus RS 485 Lightning Protection If required the RS 485 field wires should be protected by stan dard lightning protection devices EC Data suggests 15v or 16v surge protection While many venders suggest clamping surges to 6v or 7v this disregards that RS 485 can work up to 12 volts Clamping at too low of a voltage can lead to the RS485 drivers operating at near short circuit conditions and dniving at the full current This can cause over heating of de vice and or power supply 4 6 Physic al installation The unit mounts on a standard DIN rail as listed in the specification EC D485ic User Manual Block 208 Hougang Street 21 04 213 Singapore 530208 Tel 65 62843373 Fax 65 62857 737 5 TECHNICAL SPECIRCATION 5 1 RS 485 port Desc nption om 5 1 2 one ie 5 1 4 5 1 5 5 1 6 5 1 7 5 1 8 2 wire Signals D A D A and Gnd A D 8 D B and Gnd B Duplex half duplex direction auto Matic Line Voltage 7v to 12v permits 7vdc ground difference between devices Bias 470 pull up D A D 8 470 pull down D A D B jumper selectable Bus Termination 120 jumper select able Official maximum Bus Length 1
6. erefore support high baud rates The isolated power supplies and optical data signals complete the galvanic isolation re quired 2 3 RS 485 Bus Transceiver Line interface driver receiver chips convert the field signals to standard TiL level signals The full EIA RS 485 specification is meet by using SN75176 compatible chips Since 2 wire RS 485 Is a bi directional bus it requires the transmit ter receiver circuit to switch between transmit and receive asappropnate the ECD485ic uses www ec data tech com 2 of 6 an effective method to do this with 100 soft ware transparency 2 4 User Indication Ti gt lsolated Comm Device www ecdata techcam A G A E O a DB u i E D The face of the ECD485ic is shown above Green LEDs Pwr A amp Pwr B light showing iso lated power is available from the isolated DC to DC converters Yellow LEDs Rcv A Txd A amp Rcv B Txd B light when data is received and transmitted on the respective port RS 485 is port A RS 232 is port B 2 5 Signal Conditioning For nomal operation the ECD485ic has 6 jumpers installed to terminate and bias the RS 485 interface These are only removed when more than two 2 units of ECD485ic are con nected to the same RS485 wire pair For example if 4 units of ECD485ic connect to a wire pair at least 2 of them must have all 3 jumpers removed Both ports have transient suppression diodes rated at 500w or highe
7. ked either by a bar over the name ora leading An example would be DATH DAT or DAT DAT Generally the and not terminals correspond to A but ven dors are free to label them opposite here as well A direct method to determine the absolute A B terminals would be helpful If your asyn chronous device outputs a voltage when idle then the terminal with the higher voltage is Unfortunately most devices will show no meas urable voltage difference between their terminals save devices are nomally in receive mode and do not affect the terminal voltage 4 INSTALLATION 4 1 Making Standard RS 232 Cables The ECD485ic has one 9 pin female connector which looks like a 9 pin modem or DCE port cable with Cable with 9 nin male ECD4a3ic port B Cable A host with 9 pin DIE port www ec data tech com 3 of 6 4 Hin female Red 2 a fbbon cable can be used 2 Ra host with 9 pin male cable 9 pin r Txd Rxd Gnd rdc485ic EC DATA TECHNOLOGIES PTE LTD specialist in Electronics amp Data Communication cable with Cable with g EN E Eai a a 2 B Cable C host with 25 pin DCE port 4 2 Plan your RS 485 wiring Screw Teminal Models cc amp cd For 2 wire RS 485 all terminals connect to one wire of the pair and all terminals to the other wire ASa convention EC Data suggests choosing the darker wire or solid color for and lighter color or
8. more robust than 2 wire with low quality cable or high environmental noise It also reduces the data communication interrupt load on the dave devices Note that there is a special form of 2 wire RS 485 which allows an optional 2nd wire pair to be used asa control RTS signal to manage repeaters in the system EC D485ic User Manual EC DATA TECHNOLOGIES PTE LTD specialist in Electronics amp Data Communication Block 208 Hougang Street 21 04 213 Singapore 530208 Tel 65 62843373 Fax 65 62857737 2 FUNCTIONAL DESC RIPTION ag NTA Ath lscation pem Mu tpant Eu lool ahday t Pon donning Twista vor Cat imala Fisl F srt 2 1 Isolated Power Supply A power conditioning circuit steps 9 36vdc down to a stable filtered 5vdc High isolation DC to DC converters convert this to one or two isolated 5vDC supplies In all models 2p and 3p RS 485 port A hasa fully isolated supply In the case of full 3 of 3 port galvanic isolation models option 3p RS 232 port B also has an isolated supply while in the partial 2 of 3 port galvanic isolation models option 2p RS 232 port B is powered directly from the filtered 5vdc without isolation 2 2 Optical Isolation for Data Signals Digital opto couplers are used to move the data signals between the two sides of the con verter These are supenorto the more common analog opto couplers as they add little distor tion and th
9. nication Block 208 Hougang Street 21 04 213 Singapore 530208 Tel 65 62843373 Fax 65 62857737 Offers the option of 9 pin d sub shell con nector AT style or large capacity 2 5mm compression screw terminals giving maxi mum flexibility in installation in panels and terminal boxes 9 pin female DCE like ports allow use of ribbon cables from 9 pin computer ports 600 watt transient suppresser diodes are Installed on isolated ports 600w for Ims with less than lpsec response to over voltage 1 2 What is RS 232 RS 232 is an inter face standard not a data 7 Communication ASCII I Standard This means it can only go short dis tances and has very limited dnving power It provides full duplex point to point data transfer between two devices The signal ground is in cluded as one of the wires so it is very susceptible to damaging ground loops Data is transmitted asa voltage polanty relative to the common signal ground For example here is the signal for an ASCII character I When sig nal voltage gt 3v then the data isa binary 0 When signal voltage lt 3v then the data isa binary 1 A voltage signal between 3v and 3v is undefined An idle line without data will be in the binary 1 state This voltage signal ref erenced to a shared ground is quite susceptible to noise plus the existence of the ground wire leads to grounding and surge
10. problems www ec data tech com lof6 1 3 What is RS 485 RS 485 is a half duplex data communication standard which can be use for point to point or multi drop applications It uses twisted wire pairs Data is transmitted by a differential volt age signal The two wires in a pair are nota loop both are signals sourcing curent to a third virtual ground conductor For example here is the differential signal for an ASCII char acter l Though labels vary from vendor to vendor one wire of the pair is often labeled A and the other B Data is represented by the relative voltage of A to B When V lt Vp then the data isa binary 1 When V gt V then the data isa binary O An idle line without data will be in the binary 1 state This differential voltage sgnal is quite robust and not susceptible to noise or minor shifts in signal reference ground 1 4 Two or Four Wire RS 485 2 wire RS 485 is strictly half duplex One wire pairis used asa bi directional bus first transmit ting a request and then receiving a resoonse Many industrial products support both 2 or 4 wire RS 485 Providing terminals for 4 wire they allow extemal jumpers to short the two A signals and two B signals for 2 wire 4 wire uses two twisted wire pairs one for transmit and one forreceive The Tx pair is used by a master device to communicate with the Save devices and the Rx pair is used by the Slave devicesto respond 4 wire RS 485 is
11. r 3 DETERMINING RS 485 TERMINAL NAMES Due to a lack of naming conventions wiring multi vendor RS 485 devices often involves wir ing apples to oranges It may require some bench top expenmentation While this sounds bad it is often required when integrating multi vendor systems Neither the RS 485 nor the RS 232 interface can be damaged by reverse wir ing or short c irc uits to ground 3 1 Per EIA 485 EIA 485 defines the labels A and B to be used as follows Voltage of A shall be negative in respect to B fora binary 1 Sounds simple EC D485ic User Manual EC DATA TECHNOLOGIES PTE LTD specialist in Electronics amp Data Communication Block 208 Hougang Street 21 04 213 Singapore 530208 Tel 65 62843373 Fax 65 62857737 Unfortunately there are two common logic systems Computer systems treat Ov and 5v as O and 1 respectively while the most common RS 485 chips label and telecommunications treat Ov and 5v as 1 and general O respectively To avoid the issue many vendors select other na ming conventions 3 2 Determining temninal names EC Data names it s A B terminals as and respectively since when measured by a volt meter the A terminal of an idle asynchronous RS 485 data line will be a lower voltage than the B terminal Another common naming conventions is to label them as X not X where X isa name like DATor BUS and the not condition is mar
12. striped for Since the bus is bi directional all terminals and both transmit and receive when appropnate Re member RS 485 isNOTa loop On the ECD485ic the top screw terminals are physically labeled D A D A Gnd A On the removable terminals this is labeled T T R R SG Note that the important thing is the and inthe names The D A top terminal and the T terminal are intemally connected as are the D A and T With 2 wire RS 485 you can easily use 2 wire lugs on the Port A side great when you are doing a multi drop bus without stubs It is also critical that the Signal Ground be propery connected you void your wanantee if you do not connect this ground propery If your RS 485 bus does not have the 3 ground wire then you should at least connect the Sig nal Ground Gnd A or SG of RS485 to the nearest device s digital ground 4 3 Plan your RS 485 wiring D Sub Shell Models dd Cable with cable with g pin male g pin male ECD4aSic port A ECD4asic port A EC D485ic User Manual 29 ar male host with 25 pin Bae DCE Block 208 Hougang Street 21 04 213 Singapore 530208 Tel 65 62843373 Fax 65 62857737 Standard RS 232 Rees YS 28 annot be cable with cable with da pin male 9 pin male cp ER a Le ECD485ic a A ECDASSic port A RS 485 2 wire Cable With the 9 pin D sub shell option for the RS 485 the same 2 or 4 wire signals are availa
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