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Old April 6th, 2020, 03:13 PM   #1
Rson
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Standard PLC search

Warning! Long read!

I find myself in a position of being able to influence the overall controls design at my current job. However, I still have to get everything by the owner who looks at the nickels and dimes (and doesn't 100% understand PLCs - but understands relay logic)

So, I'm trying to convince my employer to switch everything over to PLCs (yes, I still design many relay control panels unless the customer wants a PLC) to allow us to basically build the same panel for nearly everything we do. In sitting down and figuring the I/O, it appears 90% of what we build could be done with 20 DI and 16 DO - with an occasional extra 8 inputs or outputs depending on the options.

I personally would love to just put an Allen Bradley micrologix 1400 in every machine, but at ~$700 + for the PLC and I/O I would need, I can't totally justify that cost to my boss - a relay panel is cheaper. In sitting down and calculating the 'cost savings' (ie, relays, push buttons or pilot lights I wouldn't need with a PLC) I figure my budget is around $400-500.

A few of the Automation Direct PLCs look to fit that mold (DL06 or Click), as well as maybe something from the micro 800 from Allen Bradley. Anyone have any experience with any of these? What PLC would you bet your job on putting in every machine with these I/O requirements?
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Old April 6th, 2020, 03:38 PM   #2
BachPhi
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20DI & 16DO is perfect for MLX1400. I bought Ebay for new one at $300
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Old April 6th, 2020, 03:51 PM   #3
cjd1965
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look at siemens s7-1200
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Old April 6th, 2020, 03:51 PM   #4
Rson
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Quote:
Originally Posted by BachPhi View Post
20DI & 16DO is perfect for MLX1400. I bought Ebay for new one at $300
The 1400 only has 12 outputs. I would need an output card (extra $150). My rockwell supplier lists the 1400 at $609, but I have been able to find them for around $450 or so elsewhere.

I need a constant supplier and to not worry that it will be obsolete in 5 years or so.
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Old April 6th, 2020, 04:08 PM   #5
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I would look at the Do-More BRX line from AutomationDirect. They have models with 20 in and 16 out and can expand up to 8 modules. The ethernet model is $463 and the serial model is $299.
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Old April 6th, 2020, 04:12 PM   #6
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What about your design time? Surely standardizing on a PLC would save a ton of CAD time vs. relay logic?

I second the Siemens S7-1200. Last I checked, there were models similar to a ML1400 for around $300?

I've not used the Micro 800 line but I've never heard of them having reliability issues.
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Old April 6th, 2020, 05:38 PM   #7
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You mention needing fewer parts, such as pushbuttons and indicator lights. Does that mean you are planning on using an HMI? Is that in your budget calculations?
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Old April 6th, 2020, 05:44 PM   #8
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Do you just intend to replace the relay system you have now or do you have an eye to add functionality in the future?
Are you going to pair this with a small, cheap HMI or will you stick with the pushbuttons and indicators? This is a separate discussion, I guess.

The S7-1200 would future-proof you to a large degree. It has a whole boatload of power and functionality. And if you can really get them for $300 it is a no-brainer from a hardware standpoint. However, the software might spank you a little.

If it is just for today and will be a relay replacer just about anything on the market will be able to cover what you are doing as long as you can get the I/O. The Automation Direct stuff is pretty inexpensive and I have always had pretty good luck with it. I haven't gotten into any of their new stuff (Do-More or Productivity) but the DL06 is reasonably capable.

Keith
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Old April 6th, 2020, 05:45 PM   #9
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The cost of a $700 PLC is offset greatly compared to:

Drilling, tapping holes & installing a bank of relays & DIN rails
Writing the logic by running wires between many relays, where the PLC rungs are included in the price
Any updates in a PLC are code changes, relay panels usually require more relays and rerouting and adding wires.
And, then there is the manhours of labor doing the above.

I was told (back in the 90's) that if a panel needs more than 3 relays it is less expensive to use a PLC.

With experience I think that is really 2 relays.
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Old April 6th, 2020, 05:48 PM   #10
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The quickest payback for a PLC over relays is when you need multiple timers.
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Old April 6th, 2020, 06:51 PM   #11
Rson
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Thanks for all the replies so far.

If I had my choice, I'd put an HMI on everything as well. We do a lot of outdoor panels as well, so that makes it harder to justify an HMI.

I have a lot push-back against using PLCs at my company. Many of the sales-people, designers, and owner are older (in the business 30 years or so) and don't feel the equipment we make justifies use of a PLC. They view it as a money sink (which I have proven wrong) and a time sink (sure - you save X time, but now you have to program it).

It doesn't help that my predecessor wasn't very good at his job and often quoted expensive PLCs and spent exhaustive time on the programming end. Most of the projects we do I can program in a morning or afternoon; and if I can get them to switch, 90% or more would be a direct-dump with a short panel check-out - maybe 1 hour. I know it is a time saver and a money saver, but I think there is a fear that I work black magic - and if I'm gone they won't be able to find someone who can do the programming. (there is certainly no one else on staff who can do it).

I've looked at the siemens stuff too - I like the 1200 series - but we have many customers who either love siemens (they spec it) or spec anything BUT siemens - so I'm not sure it would sit with the sales team as a standard.

I mentioned the automation direct stuff because some of the companies they used to have do panels for my company used the DL06 line on some projects - so my company sees it as a 'standard'.
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Old April 6th, 2020, 06:56 PM   #12
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We use a number of Micro830's in our smaller machines. You can do quite a lot with them, and if you are coming from relays then the software and inability to program online won't be an issue for you. I have been curious about the Koyo Click PLC's for a number of years now, and I believe cost vs. features and ability; you probably won't get much better than an Ethernet Click.




EDIT**

There are also a number of other items your sales people will like. e.g A PLC will allow better diagnostics and can allow for remote troubleshooting if you use Ethernet and an access modem/router. In my experience, once you upgrade systems like these, you tend to find a number of things you can now do (And do better), so there are usually other advantages.

Last edited by Jeev; April 6th, 2020 at 07:01 PM.
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Old April 6th, 2020, 07:00 PM   #13
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RA are pricing the MLX to steer people towards AB Micro_8xx.

I wouldn't use an MLX as a base price for comparisons.
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Old April 6th, 2020, 07:38 PM   #14
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+1 on the A-B Micro830. Programming software is free (Connected Components Workbench), is expandable if you even end up needing analog and if you end up needing more (Micro850) or less (Micro820) I/O, the programs are portable.
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Old April 6th, 2020, 08:28 PM   #15
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Quote:
Originally Posted by jraef View Post
+1 on the A-B Micro830. Programming software is free (Connected Components Workbench), is expandable if you even end up needing analog and if you end up needing more (Micro850) or less (Micro820) I/O, the programs are portable.

And you still have the option of Ethernet or the PanelView 800 HMIs. It might not be the cheapest, but it works and it won't be far off.
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