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PLC LAW #1 - DON'T OVERCOMPLICATE THE SIMPLE.

PLC LAW #2 - MAK E SURE YOU PLUG TH E CABLE IN BEFORE

YOU TRY TO FIGURE OUT WHY YOU CAN'T GO ONLIN E.

PLC LAW #3 DURING STARTU P, ALWAYS VERIFY I /O BEFORE

TESTIN G THE PROGRAM

PLC LAW #4 WHEN CONNECTIN G YOUR LAPTOP TO TH E PLC,

DON'T TIGHTEN T HE SCREWS ON THE SERIAL CABLE AT THE

LAPTOP SIDE.

PLC LAW #5 Read t he m anual BEFORE t rying t o

ins ta l l /com miss ion an unfami l ia r p iece o f hardw are.

PLC LAW #6 Al lw ays have al l possib le bac kup f i les (p lus read

from PLC etc .) before st ar t ing any changes. . .

PLC LAW #7 Al lw ays double chec k you have t he r ight c ables for

your CPU type and back up ins ta l l so f tw are w i th you before you

step on t he p lane.

PLC LAW #7.1 When w ork ing in a LAN or WAN environm ent

a lw ays t r ip le c heck processor ID's before eras ing and

dow nload ing new code.

PLC LAW #8 - Each vendor has their ow n programm ing sof tw are,

so p lan acc ord ing ly .

PLC LAW 8.1 - Some vendors sof tw are may not p lay w el l

w i th others. . . See RSLinx . ..

PLC LAW #8.2 - Order the correc t sof t w are f rom your vendor

inst ead of asking for i t on MrPLC

PLC Law 9 - When pow er ing up a PLC t he f i rs t t ime, mak e sure

that t he pow er supp ly vo l tage sw i tc h is se t t o the r ight vo l tage.

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PLC LAW #10 Try to st age and test as muc h as possib le before

mak ing b ig changes.

PLC LAW #11 Spares should not s i t of t he shel f . They should be

used for t ra in ing and t es ing.

PLC Law 11 .1 - THERE MUST BE SPARES FOR CRITICAL

PARTS!

PLC LAW #12 Programs should have m any rungs of d i agnost ic

ladder that can be enabled or d isab led qu ick ly . Th is inc ludes

t im ers for t imeouts . These determine w hen input dev ices are not

w ork i ng proper ly . FIFOs are good for logging real t i me event s.

Counters that count er rors are handy too.

PLC LAW #13 The best PLC programs are able t o recover f rom

error cond i t ions qu ick ly . Th is can mak e a b ig d i f fe rence t o

overa ll p roduct ion.

PLC LAW # 14 A LL PROGRAMS SHOULD BE WELL DOCUMENTED

PLC LAW #15 MAK E SURE YOU ACTUA LLY U NDERSTAND THE

QUESTION IN THE DIALOG BOX BEFORE HITTI NG "OK "

PLC Law #16: Remember t o put a paper copy o f t he la tes t PLC

ladder in the e lec t r ic a l cab inet .

PLC Law #17: When al l else f ai ls, add a TI MER, and a one-shot

too jus t in case.

PLC Law #18: When a non PLCit e te l ls you t hat a m achi ne is not

w ork ing because o f "programm ing er rors" , ask for proof before

changing your masterp iece.

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PLC Law #18.1 : When the m achine is dow n, the b lame w i l l

be ass igned to w hichever component the person ass igning

the b lame unders tands the least .

PLC Law #18.2: Americ an Money says " In God w e Trust" -

w i th PLC's a l l o thers br ing re levant data .

PLC Law #19: Mak e sure that your PLC and or process w i l l run

w i thout the HMI ( i f us ing one).

PLC LAW # 20 A good program mer w i l l never bel ieve t he guy

w ho says noth ing has changed s ince i t w orked.

PLC LAW #21: Make sure t hat t he defaul t set t i ngs doesn' t cause

the PLC to fa i l f rom s t ar t ing to operate proper ly a f ter a b lackout .

PLC LAW #22 PLC Logic c an not change by i tsel f .

PLC LAW #23 - NEVER UNDER ANY CIRCUMSTANCES LEAVE

FORCES IN A PROCESSOR. TH EY SHOUL D ONLY BE U SED FOR

TEMPORARY TESTIN G WHICH MEAN S REMOVE THEM BEFORE

GOING OFFLINE

PLC LAW #24 - Alw ays be sure t hat the rung / ladder / b lock you

are t roubleshoot ing is being scanned BEFORE you mak e major

changes or spend 6 hours t roubleshoot ing i t ! ! !

PLC LAW #25 When teac hing point s on a robot , or programm ing a

v is ion sys tem t hat in ter faces w i th a machine des igned w i th a

d ia l indexer , make sure your index t ab le is on s ta t ion.. .