panic mode

MrPLC Admin
  • Content count

    2267
  • Joined

  • Last visited

Community Reputation

30 Excellent

3 Followers

About panic mode

  • Rank
    Mitsubishi Moderator
  • Birthday 12/15/69

Contact Methods

  • Website URL http://www.google.com
  • ICQ 0

Profile Information

  • Gender Male
  • Location Mississauga, ON
  • Country Canada
  • Interests many...

Recent Profile Visitors

5295 profile views
  1. Controls Designing

    Design practices must be within constraints of the applicable standards in yourplace of business and client location.    One van learn theory at school or university but everything discussed there is purely academic. When you start wrestling with real product, you need to find out what standards are applicable. You probably want to look up local national electrical standard. Some places do have electrical standard but it's use is voluntary. Also there may be specific standards that your clients insist on.    Here in Canada, there is CEC or Canadian Electrical Code. One can buy book or better sign up for a course at one of colleges. This will introduce you to a standard and how to read and interpret it... Unlike material in college that explains how to solve various circuits, this tells you what the trade standards are, how big wire mist be, how to do proper grounding and bonding, how to debate wire size, how to size conduit, how to select and apply circuit protection and much more.  Next you need to practice somewhere good... Guy that does all kind of hacks in his garage is probably not the best mentor. Try finding an integrator, preferably someone catering to automotive because they will be cranking out tons of panels fast and they don't fool around because automotive clients are generally very knowledgeable and - they know what they want.  Then you need to apply all learned to design circuits. That involves reading datasheets, making selections, sizing circuits, applying CEC, etc.  Here it is also required to approve equipment before use (law requires that employers provide safe workplace for everyone). This means getting electrical inspection done by one of approved labs, and performing safety rusk analysis.    I used to interview controls candidates and I would ask them many questions about circuits, CEC, math, programming, networking etc.    For someone wanting to do design I would ask something like: You need to design something that can lift 750L tank of water 25m in 42sec. Tank etc.  weighs 180kg. Client is supplying 600VAC 3phase power. There is no PLC, there are just push buttons ad relays. Draw entire circuit, size all components. 5min is enough, 10min is generous time but if someone takes twice as long and still gets right solution - we can still talk...   
  2. MR J3 A SERVO

    Yes.. I have seen the same when on a slow network... Second click while waiting for confirmation seem to produce second look post 
  3. Surge supressor diode

    diode is only one of several  types of suppression devices. need for suppression comes from operating principle of solenoid. basically is works like "flywheel" and opposes any current change. before solenoid is connected into circuit, current through it is zero amp. when solenoid is connected into circuit, it resists change and tries to maintain current of zero amp but it eventually gives in so current rises gradually. supposedly current settles at some value after while (say 0.5A). when output turns off, solenoid again resist change and tries to push that current (0.5A) through output. but since turned off output is high resistance (open circuit), this will result in very high transient voltage. this spike is brief but... it can damage output as well as cable etc. to put this into perspective, suppose output has off resistance of 100kOhm, using Ohms law we can see that untamed transient would generate voltage V=I*R=0.5A * 100000 Ohm = 50000V. in reality things are more complicated so there are usually other things that will dampen this transient to some degree. for example if wiring is using cable rated for 300V, it may break down at some 1500-1800V or so. this is of course bad for wiring (insulation deteriorates, lookup "lichtenberg") but... it may survive anywhere from few cycles to few hundred thousand cycles depending on case. this is also very bad for outputs - for example transistor outputs without protection will die instantly on a very first transient even if load was a tiny solenoid (drawing only few mA of current). in short - concern with inductive loads is when they - turn off.   so how to deal with this? as mentioned there are suppression devices such as diodes, varistors (MOVs), RC elements, zeners etc. diodes are simplest and most common type of protection. manufacturers of PLCs are of course very well aware of this so they always add protection - for transistor outputs! without it, transistor outputs would be unable to do second cycle on inductive load. so if the protection is included, why add additional one?  well it is not always included (they are added to transistor output cards such as OB16), for example there are other types of outputs such as relays (OX8 or OW16). another issue is that wiring may be long - wires themselves have inductive properties so diode in PLC will protect an output but it will do little or nothing to protect end of 10m long cable that is connected to inductive load such as solenoid or contactor coil (transient will be able to create large spike at the far end of the cable, away from suppressor). how does it work? diode is wired in parallel to a DC inductive load and - it must be reverse biased. when load is turned on, current flows from output to load, no current goes through diode (except some really really small leakage current). when load is turned off, inductive loads tries to keep pushing current in same direction. since output is off, no current will flow there, however now the current has closed path -  through diode. this will eliminate big voltage spike (well, it will reduce it to 0.7V above supply voltage so it will be 24.7V). this current will stop flowing once the energy stored in magnetic field is exhausted (usually this is fraction of a second). relay contacts that are used to power inductive loads erode much faster when there is no suppression device across load. also transients can cause other issues (communication failures, "random" reboots etc). but adding diodes to each solenoid takes time (labour).  https://en.wikipedia.org/wiki/Electrical_treeing https://en.wikipedia.org/wiki/Lichtenberg_figure        
  4. RS Logix 500

    that was already mentioned...
  5. What is the best way to show many comments on HMI

    it's been a while since i have used this but you can use either alarms or message list. 
  6. Contents display, word lamp?

    i see we use smae spelling for label
  7. EL6695 is a special version of EL6692 made just for KUKA. It supports safety. KRC4 must have ONE safety interface so when using EL6695 others must be deactivated. When using safety, KRC4 must be connected to primary side and PLC must be on secondary. All KUKA device description files are installed with WorkVisual: C:\Program Files (x86)\KUKA\WorkVisual 4.0\DeviceDescriptions   Attached is what your PLC will need to connect to secondary of EL6695. ESISec.rar
  8. OTL with no OTU

    another common scenario is latching individual bits using OTL (for example alarms) and clearing them with FLL, CLR or MOV.
  9. visual basic to rslogix

    no need to create duplicate topics.  to exchange data with PLC you need some sort of software to handle communication. The fastest way to get results (and support) is to use commercial ActiveX like from InGear. if you are interested in open source, check this forum for HMI you will see something for VB.NET.  or google for "vb.net hmi sourceforge". http://forums.mrplc.com/index.php?/files/category/3-hmi-sample-code/  
  10. PLC 5 ladder output unexpected behavior

    OTE is not the only instruction that can write to an output, also is the rung scanned... (are you sure?)
  11. How to protect output module from coils going bad.

    you are correct, they are inductive... without proper suppression device, this current will destroy any relay. sizing up will give longer life but suppression devices are far cheaper, smaller and lower cost than any relay you would be happy with. even with suppression devices, those cards are probably doomed. you have 24 out of 32 outputs connected to loads that draw 1.3A each. card has 8 outputs per common and maximum current for common is only 8A, not 8x 2.5A = 20A.  
  12. How to protect output module from coils going bad.

    here is a also an example of 6-pack of interposing relays, rated 5A. it is compact, low cost and relays are replaceable: https://www.automationdirect.com/adc/Shopping/Catalog/Relays_-z-_Timers/Electro-Mechanical_Relays/Slim_-z-_Card_Relays,_5A_(RS_Series)/RS6N-DE  
  13. How to protect output module from coils going bad.

    well... what is your exact situation... OW16 is quite a beast when it comes to output cards, it handles up to 2.5A per point which is above average. most outputs are rated for 0.5A or so. if the cards fail after such short period and - so often, something is seriously wrong. i would have a chat with designer to find out what ware his selection criteria and what exactly was taken into consideration. good designed system will easily last 10+ years and - without being spared or pampered. so... what is the voltage? how much current per point? what is the type of load? (inductive?) are your outputs rated for those loads? are you using suppression? is it a right type for that circuit and load size?  
  14. Convert decimal to hex manually

    exactly... https://www.panasonic-electric-works.com/cps/rde/xbcr/pew_eu_en/mn_63489_0050_en_fpwinpro_programming.pdf  
  15. convert am to fm

    check "signal converter frequency to voltage", http://www.clrwtr.com/PDF/Weidmuller/Weidmuller-Analog-Signal-Conditioners.pdf http://www.spectecsensors.com/mobile/frequency-voltage-converters.html if you are so inclined make one (DC/DC converter, VFC23 and OpAmp to get range you need).