PLC Student

[Allen Nelson]

The other usual suspect.

Jesper:

Basically, I agree with you. He needs to define what he wants the PLC for. If it's just to "play" and "learn" with, then cheap is probably best. And he needs to take the attitude that this may just be an "investment" in education, and not expect to be able to resell it. If he manages to get his money back, great! But he should know that it may not happen.

On the other hand, if he's expecting to buy something that he PLANS to resell to the company (or have the company buy for him) to use in their next PLC project, then you're right, there's a whole different set of criteria that will apply.

The typical answer given by many on this site is to invite all the major players (vendors/distributors) to the site, and show them their wares. You will be able to get a good feel then for how well he will be supported (help in troubleshooting problems, getting replacement parts in, advice on setting up the next system). Again, the price of "deliverables" goes beyond the price of the PLC. And none of this service is free.

 

[henryhughes]

Thanks Everyone for your replies.
Cost isn't a major factor, it's My Dad's business so i can pursuede him to buy whatever I need.

Some people are advising me to get a Siemens S7-200, some are telling me to stay clear of it and go for a S7-300, and an Allen Bradley MicroloGix was also thrown into the pan. Its all abit confusing, but a hell of alot clearer than this time yesterday. I've looked through our suppliers catalogues at work, and found a S7-200 starter pack Take a look the link should work, but ive had problems with time outs, if it doesnt, ill just paste the info here. And I've also found a Allen Bradley Micrologix 1000 Starter Pack Take a look , With the Allen Bradley it comes with an IBM PC to Micrologix connection cable, I dont have an IBM comp, Its a Pretty Dell one, is this going to cause a problem?. Sadly I havn't managed to find a Siemens S7-300 starter pack, from what Ive been hearing from you guys this would of been the best to go with.

To learn how these things work im planning on making a system at work, where workshop Temperatures are moniterd (excuse the spelling, its a good job there isn't much spellung involved with PLC's!), when they fall below a certain temperature (16oC) the workshop shutter doors automaticaly close, sensors will see if anything is blocking the doors, and stop them shutting if there is. Heaters will then come on automaticaly, and alarms will sound etc. Thats my idea anyway, i assume it will work, I'll probably be on here asking for help, after Ive chosen a PLC. Running before i can walk!. (I'd also like to make a noise operated one Maybe off the same PLC?) Are the 3 PLC's you've recommend capable of this?

Thanks for reading this far, and ill be greatful for any comments/replies/advice, I'll go look for the s7-300 Starter packs, and comeback in the morning why am i the only Brit using this site? lol

 

[henryhughes]

Yep, RS Site doesn't work very well, heres what you should be reading if the links had worked.

Siemens S7-200 STARTER PACK
The S7 brings to the user a powerful solution to a host of control applications, which is easy to adapt & expand the system.
The S7 is a family of PLCs which allows the user to tailor their selection of components which best suits their requirements
The S7 family is the long term successor to the highly successful S5 range. Whatever the S5 can do the S7 can do it quicker & easier
The 2nd generation of S7-200 builds on the success of the original range and exploits new technology in order to produce an optimum sized, cost effective powerful range of PLC's. The range of CPU's available has been increased, as has the range of digital, analogue and communications expansion modules. This gives the S7-200 2nd generation the flexibility to fit each application as closely to the system requirements as possible.
For the faster type of application real time control is easily achieved by use of the comprehensive range of built in interrupts. Timed, Communication, High Speed Counter, High Speed Pulse Output, and hardware interrupts are all available, and the implementation of a priority table means that all the interrupts can work simultaneously.
Communications with S7-200 is built in. Inter PLC communications is achieved using two wire network which can be up to 1200 meters and can have up to 126 nodes. In "Freeport" mode the PLC's RS485 port runs in free ASC11 mode making it possible to communicate with other devices.
In line with Siemens objective to make the programming of S7-200 as user friendly as possible MicroWin programming software has been further improved. These improvements all help minimise program development time. This has been achieved by including more and improving existing "wizards". These help program developers with the more routine/complex parts of their programs, e.g. TD200 configuration, PID loop configuration, High Speed Counter configuration, etc. Inclusion of context sensitive help also means that all the information required is at the users fingertips.
Real Time Performance

Powerful Instruction Set

On-Board Communications

Extensive User Memory

Maintenance Free Operation

Modular Expansion up to 248 I/O

Small Footprint

Easy Programming

The True Power Box is the ideal way to get to grips with S7-200 PLC’s. Included in the box is an S7-222 AC/DC/DC PLC, input simulator, motor, MicroWin V3.2 programming software and an RS232/PPI programming cable.
Also included is a System Manual and 1 and 2 hour starter guides.


Allen Bradley Micrologix 1000 Starter Kit
This family of controllers combines the flexibility of an expandable system with the small footprint of a fixed controller. The Micrologix 1000 provides a range of compact units for up to 32 I/O. The Micrologix 1200 provides an expandable solution using expansion modules to give a world class solution from 24-88 I/O. Finally, the Micrologix 1500 which provides powerful solutions from 24-156 I/O. The entire family is programmed using the Logix500 for Micrologix programming software

Compact units offering flexible control solutions for up to 32 I/O points. Compatible with the SLC 500 family, the controllers can be programmed by Logix500 for Micrologix software or by a handheld programmer.
The micrologix 1500 which provides powerful solutions from 24-280 I/O. The entire family is programmed using RSLogix 500 programming software (246-9265). Enhanced operator interface options are available from the panel view range of products.
Two packs providing an introduction to Micrologix micro controllers. Both supplied with all hardware, programming equipment, documentation.
Software based pack contents:
16 I/O controller with 24V d.c. inputs, relay outputs and 110/240V a.c. power supply

Micrologix 1000 programming software

IBM PC to Micrologix connection cable

Input switch simulator

Programming manual

Hand held programmer pack contents:
16 I/O controller with 24V d.c. inputs, relay outputs and 110/240V a.c power supply

Hand held programmer

HHP to Micrologix connection cable

Input switch simulator

Programming manual

 

[JesperMP]

Henry,
are you sure that you have considered your future needs ?

MicroLogix1200, MicroLogix1500 and S7-200 will be sufficient for the task at hand.

But I have these comments:

The MicroLogix models dont have online programming. You have to make changes offline and then download them to the PLC. Not a big deal for some, but a killer for others. Many people are using the MicroLogix's with good results though.
The MicroLogix models are yesterdays generation of AB PLCs. They are perfectly good at the moment, but AB is steering away from the PLC5/SLC500/MicroLogix and towards ControlLogix.
Try to look at a CompactLogix if you want to prepare for the future.
To get started with CompactLogix will cost you approx 2 times the amount of getting started with MicroLogix.

The S7-200 is a completely different design compared to its bigger brothers S7-300 and S7-400. You cannot share code between the S7-200 and S7-300 for example.
You could consider to start with a small S7-300 in stead of an S7-200, if your future needs will be bigger than todays.
To get started with S7-300 will cost you approx 1.5-2 times the amount of getting started with S7-200.

Of course you could get one of the small PLCs now, and then reevaluate your position in a couple of years.
But in that case you must brace yourself for the risk of having to throw out much of what you have learnt and start all over.

 

[Ken M]

Henry

Don't worry - there are UK users of this forum!

It's all very well getting so-called 'independent' or 'un-biased' opinion from a forum like this, but don't forget the users here are a very small and self-selecting sample of the PLC-using population at large. Everyone, myself included, will have a bias - whether they realise it or not.

Have you spoken to your local Siemens/Rockwell/whatever representative? Would you buy a car without at least visiting a showroom or speaking to a salesman? Ask them about current models and what they think would suit you. Don't worry about them always trying to sell you the most expensive model - make it clear you're speaking to their competitors and any salesman worth his salt will make sure he pitches his offer as competitively as he can. Also ask them about future development plans for their models. How old is the current range, how much life is left in it etc? Taking Jesper's approach of a 20-year view on this may mean you're not going to be using any current PLCs in 20-year's time. What about other bits & pieces you could source from the same supplier. Things like switches, contactors, relays, buttons etc etc. The more attractive you can make your potential shopping basket the more attention you'll get from the supplier. Use whatever leverage you can generate.

And finally, the only thing I would say is once you've made a choice, don't try to keep your options open for ever after that. Commit yourself to your choice. Invest time and effort in understanding whatever make/model you select and don't continually be looking over your shoulder wondering if you made the right decision. A good designer/programmer who knows his way around whatever PLC he uses can make more difference to the success of a project than the 'best' PLC driven by an uncertain or incompetent programmer. Set yourself the goal of being that good designer/programmer. We'll see you back here answering questions eventually!

Good luck and regards

Ken.

 

[JesperMP]

I only write this because Henry maybe wants to go the Siemens way. Thats OK by me, but it does not mean that I want to push him in that direction.

But he should know this:
Siemens has just slashed the price for its STEP7 lite (programming software for S7-300) to approx 50 EURO (!) - according to a newsletter that just entered my intray.
There is no info on a similar move on the MicroWin (programming software for S7-200) front. But MicroWin should have a new release with many improvements.

This means that there is really no price difference between the two Siemens platforms S7-200 and S7-300. To get started I mean.