Primary Logic Circuit PLC Capabilities

We always used data buckets to record data. I guess you can roll your own, but I would consider renting the equipment you need unless this is a long term project.

I agree with AH, but you might consider something like this...

http://www.dataq.com/

Yup, I meant to say Programmable Logic Controller dunno why I got that mixed up (again).

I am not familiar with ardunio or raspberry pi, are they capable of large repetitions of events? I am doing failure analysis on automatic equipment. We already have a counter on the control circuit but do not have individual counters on each part.

I was thinking of using an optical or magnetic sensor to record the actual number of successful operations. So far I have less than 20 devices operating at once in 2 different nearby locations and don't expect many more but expandability is important.

If I were to use a laptop, what device would I use to interpret the signals from the sensors.

Drew K

A little more info would be nice.

How many inputs?

What is the format of the inputs:Logic level: contact,TTL,analog,or digital?

Are all inputs of the same type,or a mixture of analog,digital and contact or TTL inputs?

If different,signal conditioning will be required.

Do you need event time recorded for each event,or simply a total of events?

How accurate must the results be?

Will you need a continuous printed record of events,in real time?

More info=better answers.

Yes you can. The term is Programmable Logic Controller, and there are many different manufacturers avialable. In general, the programming tends to have some part of the logic that is specific to the particular manufacturer, so you will need to study that area, unless you buy from a vendor that will programme your solution for you, included in the price.

You should be able to pick up an Arduino Mega at Radio Shack (or online) and download the IDE (integrated development environment) online at Arduino.cc (versions for microsoft, Apple, unix. The board has a USB link for connecting to computer and you can write a statement that outputs to the monitor in the IDE. If you need storage you can add a 30 gig. card carrier, all for less than $100.

What surprises many people is that very often the signal wiring and installation costs will be much more expensive than the "smart" modules today.

I used to pay over $700 for Analog Devices 2channel A/D and build my own gain blocks to get arc voltage and 50ma current shunt to the input range (0-5v) that the card required. By the time I added digital i/o, serial, parallel, processor, memory, and battery backed ram, cost of the STD system was about 4k, today I can do the same thing with a $40 AT MEGA 2560. There are many SOC (system on chip) devices to choose from, you just need to do a little shopping!

I have looked into the Arduino Mega online and found some laser counter circuits on instructables. I was not able to see if any of the counter circuits recorded the values in a way that could be exported instead of displayed on a lcd.

Any ideas?

Drew K

Any data that you can display can be formatted and output on the usb serial link....you can display this data with the monitor program in the IDE, or use a routine to listen to the port and take that incoming data and format it for a spreadsheet or wherever else you are going to stick it.

You might look at instructables that write gps or weather station info to an SD card, or transmit that info to wifi or bluetooth.

UC Boulder has info on doing these things with a 'PCDuino', a Ubuntu unix based, Ardunio shield compatible board for about $80...plug in an HDMI monitor, USB expander, keyboard and mouse and link into the nearest WIFI and you're up and running.

The Arduino website also has examples.

When I want to check digital i/o, I just add a line that formats the state as L/H or 0/1, (ordered in groups of 4 for easy mental conversion) with a Serial.println("example=" + string (variable to display)); statement, the value having previously been written to the variable...you can set the format however you want.

LoL! You make it sound easy...so where do I start to begin learning what I need? Can you recommend a book or website?

Drew K

Drew,

I had to tackle a PLC project recently that I really didn't want to start because there was so little documentation. I had to replace a HMI (Human Machine Interface) project that was really old. After avoiding the project for a couple of years, I finally got to the point where I had to figure something out. Getting it done by an outside contractor was way out of the question. Now, I'd like a piece of that pie for myself!

I ended up downloading and testing the HMI software free for 40 hours of computer run time. I highly recommend that as a starting point. But before you do that, spend some time with the free online training videos they have. You'll find them under training menu of their website. You probably want to use the Trending features to monitor the signals you mentioned. But they are likely to be able to talk with your PLC and download all the variable names from the existing program. That is a big time saver! By the way, you may want to learn/experiment on a PC other than the one you intend to use for data collection. You can download it to as many computers as you have but after 40 hours or weeks of non use, it goes into demo only mode. Otherwise, it is a full blown package until it times out. Very, very powerful and easy to use with the free help and training!

I'm still a beginner myself with www.indusoft.com but they really rock! Good luck! Let us know how it turns out! I can't wait until I get another project! I still have unused license to play with!

All those sites I mention in #15 are free and those routines can be studied and you can figure out what you need. Instructables can be searched and thats also free unless you want to download PDF files, then you have to be a member.

PLC's have very limited on-board memory and the memory that is there is limited to use for processor and I/O functions.

PLC's do not allow labeling, descriptors, or commenting of addresses within it's memory and require external memory storage to do so.

The DATA gathered by the PLC must be dumped into a computer with enough memory for meeting your DATA storage capacity requirements.

Once the DATA is properly stored you must either develop an EXCEL spreadsheet or other form of DATA manipulation program or purchase a software package expressly designed to accept, store, display, and/or trend the DATA for further use.

Just noticed a post on Instructables.com by Crtek concerning writing data to Excell and a phone display, if you look that post up on the right you will also see related posts on data logging.