Tacho Read out For HMI Screen

[denise01 3]

Hi I want to display a Speed Indication on a NS 5 Screen reading Revolutions per Hour. Am okay with the NS side but not too sure what I would need to use to capture the data accurately. i will use a proximety sensor seeong a rotating flag. Thanks Peter

[Geir 4]

If you have a PLC with "built-in" IO (CP1x), there is the PRV instruction that will give you the frequency. CJ1M ver 3+ with "built-in" IO even have the PRV2 instruction that will give you rpm directly.

[denise01 3]

Hello, Yes I have a CJ1M CPU 11 running with CXP. So is the Instruction to use PRV2. If so will programme and try. Many Thanks Peter

[ParaffinPower 13]

Hello denise01 The PRV2 instruction only relates to plc's with built-in high speed IO (CP1, CJ1MCPU2x) so is not appropriate if you have a CPU11. If you want to display rotations per hour, then I'd count pulses in a minute and perform a rolling average of these over 60 minutes FIFO-ing the array of readings. The problems of inaccuracy due to timings won't be relevant if you're averaging an hour's worth of pulses I don't think. If you want rpm, then scan time becomes an issue, or should I say or striking a balance between precision, stability and responsiveness of the readout. I have an FB that looks at the plc's internal clock which does a pretty good job of this. However, it's on another pc. Next time I'm on that, I can post it, if it'd be useful. Pp

[denise01 3]

Hello Paraffin Power, Not sure what you mean by FIFOing but any help you can send would be appreciated. I really need something that shows the speed in Revs per Hour and of course shows zero when the machine stops. Regards Peter

[ParaffinPower 13]

Fifo = first in first out. Each minute, move the latest minute's data in, and the oldest data out. This gives a rolling total, rather than just counting how many pulses there have been in the last hour. There are ladder instructions for stack control, but I'd roll my own in an ST FB. Pp

[denise01 3]

Okay Paraffin Power, Did you say that you would post an example. Regards

[ParaffinPower 13]

Hello again This uses the plc's internal clock (ie if fairly oblivious to scan time), and updates the rate each clock pulse. The DistanceBetweenPulses input parameter was so it would give you m/min or inches/min or whatever you want. If you just want pulses/min then make this +1.0 A oneshot FB is nested. It pulls this in automatically, so don't worry about that. Pp RateCalculation.zip Edited 23 Apr 2012 by ParaffinPower

[denise01 3]

many Thanks Paraffin Power, Will put in to programme tomorrow and trial. Am really impressed with NS 5, very versatile. Regards

[denise01 3]

Hello paraffin Power, Not sure what to open the ZIP file with. Please advise. Regards

[ParaffinPower 13]

Winzip. Think it's native in windows (speculation). If not, there must be freeware available Pp

[denise01 3]

Just tried to open with cxp ver 9.3 which is what I use but wouldnt open

[ParaffinPower 13]

Attachments here need to be zipped. Use winzip (or similar) and extract the .cxf file. This can be imported into a cxp project by right clicking on the function block section of the project tree, and then select 'from file'. This will make the fb available for invocation in your standard ladder. Pp

[denise01 3]

Hello Paraffin Power. i have not really got in to FB yet but am assuming I feed the info in to a FIFO and then put the first stack reading in to the Data Memory area and transfer to the NS 5 Regards

[ParaffinPower 13]

Hello The FB maintains a stack of the 10 most recent timings internally, and averages them each time a new entry is made. There's no need to do anything externally. Pp

[denise01 3]

Okay Pp but how is the data applied to the NS 5 and how is the address of the 1 shot sensor addressed

[ParaffinPower 13]

Invoking the FB in your ladder will allow you to attach the 'real-world' addresses to the FB via the Input and Output parameters. Have you got the FB in your ladder yet? It's fairly self-evident once you have. Pp

[denise01 3]

hello Pp, Yes I have inserted the FB in to my ladder programme I take it that the one shot FB uses the sensor I have picked as the input and the output is used in the rate calculator. I have never used FB before so I guess it is a question of reading the parameters in the FB and transfering them as addresses in the ladder diagram.Its a good learning experience anyway once I have sussed it I will use it a lot. Regards

[ParaffinPower 13]

The oneshot fb is nested; don't worry about it. The idea of a fb is to encapsulate some code so you would rarely (never) address its internal memory. Anything you need from, or presenting to the outside world would be presented as an input or output parameter. This is the case on the example fb provided. Clear as mud? Pp

[denise01 3]

Hello Pp will you have a look at what I have done in the ladder diagram to see if its right its at the end of the counting circuit section. Like I said I am new to FB anyway Thanks L2BODIESMASTER260412nsstufffbstuff.cxp

[ParaffinPower 13]

Hello Herewith my comments: 1. I don't know what the ADD instruction on the ENO is supposed to be doing 2.The DistanceBetweenPulses is a REAL, so needs to be entered in the format +1.0 3. The Pulse and Running parameters need to be something other than Always Off 4. The other addresses are all 0; the inputs need populating, the outputs are optional (but the result will appear in one, or both, of them 5. Bare in mind, this was an example rolling average FB; it won't produce wotsits/hour 6. The 'Tweak' parameter was intended to give a bit of calibration; +1.0 yields no calibration will be applied, +1.1 will give 10% over. Hope this helps point you in the right direction. Pp

[denise01 3]

hello Pp In the end I went with a simple programme please see it gives speed but not as good as maybe the FB just cant suss it. Regards Peter average count.cxt.cxp