Programmable Logic Control (PLC) Supplemental Material

Transcription

1 Programmabl Logic Control (PLC) Supplmntal Matrial Intrdisciplinary Automatic Controls Laboratory - ME/ECE/CHE 389 Fbruary 5, 206 Contnts Laddr Logic. Exampl Laddr Logic Program Stting up RSLinx and RSLogix 3 2. Stting up RSLinx Using RSLogix: Editing Downloading and Running Programs Configuring RSLogix Downloading and Running Programs Laddr Logic with RSLogix Tutorial 6 4 Basic Laddr Logic Instructions with RSLogix 7 4. Rcommndd Rading Bits Chaptr Inputs Outputs Output Latch (OTL) and Output Unlatch (OTU), Chaptr Examin Opn Examin Closd Count Up (CTU) Chaptr Timr On-Dlay (TON) Chaptr Mmory Push and Mmory Pop (7-0) Laddr Logic A programmabl logic controllr, or PLC, can b usd to control any procss that rquirs automation, such as procsss found in a chmical plant, automatd machinry, or laboratory quipmnt. Whn usd in such a procss, th PLC is programmd to prform a st of logical stps in a spcific ordr to complt th dsird task. Ths stps ar programmd into th PLC using a laddr logic program, which consists of a spcific st of instructions which will b usd to dfin th procss and control th machin.

2 Laddr logic is a graphical programming languag that uss diagrams similar to lctric circuits to ntr a program into th PLC procssor (MicroLogix 000 in our cas). Th controllr taks in inputs from th laddr logic, procsss th input data basd on xisting conditions, and snds outputs to th machin or procss. Th laddr program ntrd is a spcific st of instructions providd for th controllr to follow during control of th procss. A laddr diagram (Figur ) graphically shows ach of th spcific stps that th controllr must follow in th control circuit opration. Figur : Laddr diagram. Th lft sid of th laddr rprsnts a liv wir through which information flows. Although th controllr is abl to scan th ntir laddr logic program instantanously, it must still procd through th control procss in th logical pattrn. This is accomplishd through th us of gats. Th gat rprsnts th input on th rung of th laddr diagram. Th two main gats usd in th laboratory ar OR and AND gats (Figur ). Th OR gat is similar to a paralll circuit, whr if ithr on OR th othr switchs ar closd thn th output sid of th rung will bcom nrgizd. Th AND gat is similar to a st of switchs connctd in sris. If th input rfrring to th first switch AND th input rfrring to th scond switch ar both turnd on, th gat is closd, and th output sid of th diagram bcoms nrgizd. Ths typs of gats can b arrangd so that th outputs ar nrgizd to prform som logical sris of oprations. Whn th gat conditions ar satisfid, th output instructions, which ar locatd at th nd of th rung, ar activatd. Only two output instructions ar ncssary to carry out th labs in this cours: initialization of bits and activation of xtrnal switchs. Th initialization of bits nabls nw rungs to b activatd. Th activation of xtrnal switchs activats or dactivats physical oprations; i.. th signal snt from th controllr causs a pnumatic valv to opn which, in turn, xtnds a piston in a piston-cylindr dvic. In laddr logic, ths output instructions ar accomplishd by loading and unloading bits and outputs, which subsquntly nrgiz a rung to load or unload an output. Each symbol ntrd on a rung in laddr logic is givn an addrss which consists of a lttr and a numbr. Th lttr rprsnts various functions, whil th numbr allows for distinction. In this laboratory, th lttrs usd and thir dfinitions ar as follows: I Input input to th controllr from an xtrnal sourc O Output output from th controllr to an xtrnal sourc T Timr sts tim btwn oprations in th program B Bit usd to activat dsird rungs in program or stor information L Load loading of dsird opration U Unload unloading of dsird opration 2

3 . Exampl Laddr Logic Program On th first rung (rung 0) of th laddr diagram, ithr Input (I) or Bit 2 (B2) must b closd to nrgiz th rung. If th systm is xprincing initial start-up, thn it will rquir an xtrnal input, such as prssing a button or a switch, in ordr to bgin th control procss. If this is th cas, thn th manual loading of Input will b rsponsibl for nrgizing th rung and activating th outputs on th right half of th rung. In this cas, th output loads bit B0 as dsignatd by (L) and unloads bit B as dsignatd by (U). Th loading of bit B0 closs th gat on rung, which initiats timr T0. A timr waits for som prdfind amount tim to laps and thn loads a corrsponding Timr-Don-Bit. In this cas, timr T0 closs timr-don-bit T0/DN, which nrgizs th rung and activats its outputs. Rung loads output 0 to prform som physical opration, loads bit, and unloads bit 2. Th program procds similarly to rung 2 and thn loops back to rung 0. Th program will continu to loop through rungs 0-2 until th xtrnal input I0 is activatd, which unloads all th bits. Rung 3 is includd in th program as a mans of turning off th machin and as a safty rung. It is not ncssary for th actual systm movmnts and controlld stps, but is ncssary as a mans to stop th systm and rturn all actions to thir initial stat. Not, th systm will continu to loop through rungs 0-2 until this safty rung is activatd by input I0. Aftr I0 is initializd, th bits that wr loadd during th procss ar ach unloadd so that ach is rturnd to its initial stat whn th systm is turnd off. This way, th systm can b haltd at any stag during th procss. 2 Stting up RSLinx and RSLogix Two programs will b ndd for writing and diting laddr logic fils and downloading thm into th PLC procssor. Th first is RSLinx which will b usd to stup th communications btwn th PC and PLC procssor. RSLinx must b stup proprly and rmain opn whil diting and running th laddr logic programs. Th scond is RSLogix which will b usd for diting th laddr logic program and downloading it to th PLC procssor. 2. Stting up RSLinx. Navigat to All Programs, Rockwll Softwar, RSLinx, and opn RSLinx Classic 2. Chck that th PC and PLC ar communicating (if not you nd to configur drivrs) (a) Slct Communications drop down 3

4 (b) Slct RSWho (c) Confirm that th PC and PLC ar talking to ach othr, th Link is blinking (d) NOTE: RSwho just brings up th drop down tr which may alrady b visibl 3. Configur drivrs (s TA for hlp on this stp) (a) Slct th Communications drop down mnu (b) Slct Configur Drivrs (c) From Availabl Drivrs Typs drop down mnu slct RS-232 DF dvics and click Add Nw (d) Click Configur on th right () Slct th appropriat Comm Port (this is th particular USB port that is connctd to th PLC procssor) (f) Click Auto-Configur, click OK, click Clos 4. Do not clos RSLinx: It must rmain opn in ordr to download laddr logic programs into th PLC procssor with RSLogix. 2.2 Using RSLogix: Editing Downloading and Running Programs RSLogix is usd for diting laddr logic programs and downloading thm into th PLC procssor so that thy can b run on th physical hardwar. Th xtnsion.rss is usd to dsignat laddr logic program fils to b run with RSLogix. A sampl.rss fil is availabl to hlp familiariz yourslf with th programming functions of RSLogix Configuring RSLogix. Opn RSLogix Navigat to All Programs, Rockwll Softwar, RSLogix Micro English, and opn RSLogix Micro English 2. Opn th sampl.rss fil which can b found on th controls driv. T:\PLC 02 TrafficLight\Laddr Fils\RSLOGIX TUTORIAL ME389.RSS 3. Ensur you ar proprly connctd to th PLC procssor (a) On lft sid of RSLogix, th program tr should b visibl (b) If program tr is not visibl you can rturn to th dfault viw by slcting Window drop down mnu, Arrang, Dfault Projct, OK (c) In th Program Tr, xtnd th controllr foldr, doubl click Controllr Proprtis (d) Slct Controllr Communications, click Who Activ () Slct th MicroLogix 000 procssor (f) Click OK, click Apply (in Controllr Proprtis), click OK 4. Now you should b abl to download and run th sampl fil. 4

5 2.2.2 Downloading and Running Programs Thr ar two stats to th RSLogix softwar, Onlin and Offlin. Whil Offlin, th laddr program can b ditd and thn downloadd into th PLC procssor. In th Onlin mod, RSLogix can b usd to obsrv th currnt stat of ach instruction. For xampl, if bit B0 is currntly activatd, it will b lit up in th RSLogix laddr diagram whil in Onlin mod. Howvr, diting th program can only b don in Offlin mod. Thr ar also two stats to th PLC procssor, Program mod and Run mod. Th procssor stat can b controlld from th PC with RSLogix. In Run mod, th procssor will carry out th most rcntly downloadd program. In Program mod, th procssor will sit idl, allowing you to mak changs to your program (not: dits can only b don with RSLogix in Offlin).. Download th sampl program into th PLC procssor (RSLOGIX TUTORIAL ME389.RSS). (a) Slct Comms drop down mnu (b) Slct Download (c) You may b promptd to switch RSLogix to Onlin mod, click ys if dsird (d) You may also b promptd to switch th Procssor to Run Mod, do so if dsird 2. Switch RSLogix to Onlin mod (if not alrady) (a) Slct Comms (b) Slct Go Onlin (c) Th laddr in th uppr lft of RSLogix will b spinning whn Onlin. 3. Switch th Procssor to Run mod (if not alrady) (a) Slct Comms (b) Slct Mod (c) Slct Run (d) Whn in run mod th lft laddr will b highlightd in grn. 4. Switch to Offlin mod to dit th program (a) Slct Comms, Mod, Program (b) Slct Comms, Go Offlin 5. Print th program to PDF (a) Slct Fil drop down, slct Print Rport (b) Undr Nam slct Adob PDF, click OK to print (c) An xplorr window should pop up to slct whr to sav th PDF 6. Not: For th MicroLogix 000, you can only dit th program in offlin mod. 7. Not: You must r-download program to th PLC bfor with any nw dits to th program. 5

6 8. Dbugging Tip: If your program cannot b downloadd bcaus of programming rrors (a) Programming rrors ar listd in th rsults window (b) Slct Viw, Chck th Rsults window (if not alrady chckd), th Rsults window is displayd at th bottom (c) Errors ar listd in Fil 2 3 Laddr Logic with RSLogix Tutorial A quick tutorial on using RSLogix to viw and download th laddr logic fil into th PLC procssor. W considr th xampl laddr logic fil in RSLogix of Figur 2. Th program is initiatd by prssing Input I, which nrgizs rung 0 and loads Bit B0 and initiats Timr T0. Timr T0 counts up to 5 sconds, thn loads Bit B3, nrgizing rung and loading Output. Finally th last rung is nrgizd by Input I0, RSLOGIX_TUTORIAL_ME389.RSS which unloads vrything. LAD 2 - MAIN_PROG --- Total Rungs in Fil = I:0 76-Micro Bit 0 0 Timr 0 TON Timr On Dlay Timr T4:0 Tim Bas.0 Prst 5< Accum 0< Bit 0 L 0 EN DN Timr 0 Don T4:0 DN Bit L 000 Bit Output O:0 L 76-Micro 0002 Input 0 I: Micro Bit 0 U 0 Bit U Output O:0 U 76-Micro 0003 END Figur 2: Exampl laddr logic program (RSLOGIX TUTORIAL ME389.RSS).. Opn th practic fil RSLOGIX TUTORIAL ME389.RSS with RSLogix 2. Download th fil in th procssor (Comms, Download) 3. Switch RSLogix to Onlin (Comms, Go Onlin) if not alrady Onlin 4. Chang PLC procssor to run mod (Comms, Mod, Run) it not alrady in Run mod 5. Start th fil by prssing Input I 6. You can obsrv th progrss of th program from th RSLogix window Pag Monday, January 05, :30:0 (a) Notic activatd instructions will b lit up in th RSLogix window. 6

7 (b) Notic th inputs and outputs can b namd to mak th cod mor radabl. (c) Notic how th rspctiv LEDs on th PLC procssor (MircroLogix 000) light up whn th corrsponding inputs and outputs ar loadd. 4 Basic Laddr Logic Instructions with RSLogix This sction brifly covrs th ncssary laddr logic programming commands ndd to carry out th ME389 PLC laboratoris using RSLogix. For mor information on ach instruction s th associatd chaptr in th MicroLogix Manual. Th instructions ndd for programming ar locatd in th box displayd in Figur 3, most of instructions ncssary for th lab ar undr th Usr tab and Timr/Countr tab. Figur 3: RSLogix Instruction toolbar. 4. Rcommndd Rading. Chaptr 7: Dtaild information ntring instructions and functions i. Important bit instructions ar Load, AND, OR (7-3) (a) St and Rst (7-8) (b) Mmory Push and Mmory Pop (7-0) (c) Timr Instructions: Timr On-Dlay (7-6) (d) Countr: Count Up (7-24) and Rst (7-27) 2. Chaptr 6: Entring and diting your program (For Handhld programmr) (a) Particularly (6-) through (6-4) 4.2 Bits Chaptr Inputs For th MicroLogix 000 inputs ar catalogd in th form I:0/0 - Input Outputs For th MicroLogix 000 outputs ar catalogd in th form O:0/ - Input 7

8 4.4. Output Latch (OTL) and Output Unlatch (OTU), Chaptr Examin Opn 4.6 Examin Closd 4.7 Count Up (CTU) Chaptr Timr On-Dlay (TON) Chaptr 6- An xampl of a timr in RSLogix is shown in Figur 4. In this cas, a Timr-On-Dlay (TON) is loadd by bit B (B3:0/). This particular timr, T (T4:), waits for 2 s, thn loads th timr don bit (T4:/DN) which loads Bit 9 (B3:0/9). Don t worry about th spcific maning of ach digit in B3:0/, TRAF VER 2 ME389.RSS just undrstand that this rfrs to Bit, and likwis, T:4/ rfrs to timr. LAD 2 - MAIN_PROG --- Total Rungs in Fil = Bit B3:0 TON Timr On Dlay Timr T4: Tim Bas.0 Prst 2 Accum 0 Timr T4: DN EN DN Bit 9 B3:0 L END Figur 4: Exampl of a Timr On Dlay (TON) in RSLogix. 4.9 Mmory Push and Mmory Pop (7-0) 8