diving in head first

tir38

Member
Join Date
May 2006
Location
Atlanta, GA
Posts
3
I'm fairly new to using PLCs and I want to teach myself more about how they work and the possible applications I can use them for. I am a recent Mech. Engineering graduate so I have the technical background to feel comfortable understanding the basic tutorials i've read so far.

I'm interested in buying some hardware and start experimenting. My question is how to go about doing this. I think I can start off small w/ a processor module, one input module, one output module, and a power supply module. I think I can get most of this stuff used on eBay for $100 - $150. Is this the best way to get started? Do you know of companies that package special "starter kits", or reduce prices for educational purposes?

Also, what additional hardware do I need to transfer logic programs from my PC to the PLC?

thanks,
jason
 
It all depends what platform you want to learn on.

AB has a free software kit for the ML1000,
Automationdirect.com has a free software for up to 100 words.

Others supply free downloads for their software, etc.

You usually need a programming cable, typically RS-232, nothing special, and if you get the manual, some you can make yourself.

If you specify the platform, I can get more specific.
 
Sometimes a local distributor of PLC's can offer 1 -2 day basic PLC training classes at a very reasonable cost. It might be worth checking into. AB and others also have classes which are very good, but because they are more in depth, take 3 - 5 days and cost $900 - $1200. If you work for a company that encourages these classes and will reimburse some/all of the cost, it's definitely worth it.
 
Don't waste your time and money on a Vendor Course. You'll get a hell of a lot more, for free, right here!

You should of course get your hands on a small system that you can play with. You would do far better for yourself by using PC based programming software, rather than a hand-held programmer. However, in a pinch, the hand-held will work... although it can be really painful developing a listing!

You'll also need to get a hold of, or make, a switch/push-button panel to simulate Inputs. You can use either the output indicators on the PLC to monitor the state of the outputs, or you can connect lights to each output. It is better to monitor the actual outputs rather than relying on the status indication in the programming software because of the communication delay inherent in status display. That is, an output might actually go ON, then OFF before the ON status is displayed on the screen.

You should be able to get a decent setup for a few hundred bucks from Automation Direct. However, the last I heard (this might be wrong now-a-days), in their lower-end models, their number system is BCD based... not the easiest thing to work with.
 
Terry Woods said:
You should be able to get a decent setup for a few hundred bucks from Automation Direct. However, the last I heard (this might be wrong now-a-days), in their lower-end models, their number system is BCD based... not the easiest thing to work with.

If you can count from 0 to 7 that shouldnt be much of an issue.. For about 300.00 you can get an Automation Direct DL-06 & programming cable, then download the free version of their software.
 
Don't overlook the very fine simulator at the top of the page.
Phil Melore busted his chops on it and it is under utilized.

I keep a DL06DR on my work bench just to play with.
Download the free manual(s) and you can learn:
1) 'Drum Switches' (your washing machine control)
2) standard ladder logic
3) STL logic
4) insomnia - trying to squash that last bug
 
Ron, regarding your post pointing to htservices, I can definitely see the issue regarding automating people out of a job. I definitely have a problem with it!

After all, if we were to automate everyone out of a job... who would be able to buy the products that we produce? Unless of course, we have driven the cost of production close to zero and the consumer cost was really tied to product production cost.

There is a serious flaw in this relationship! The flaw, of course, is greed!

I've said it before, and I will stand by it... for any company to break-even is for that company to, at the very least, maintain! That is, not going broke!

Of course, you have your competitors that are driving you to work harder for a bigger share of the market-place. But then, that is the very essence of Capitalism! The Producers are supposed to fight for the Consumers! AND YET, at the same time, those workers involved in producing MUST have the ability to participate in the Producing/Buying process!

Since the workers (buyers) have very little, if any, control of the current monetary situation, it is entirely up to those that do do have control (those that have) to act reasonably in terms of those that do not have. That is, they, those that have, need to control their damned greed so that ALL of the others, workers/buyers, can continue playing the game!

If that relationship is not properly maintained, then we can't help but fall into what was called serfdom, or, into what many of you can recognize in a more contemporary sense, slavery.

Before long, we, the enslavers, through automating those others out of their jobs, will soon be enslaved!

My philosophy is to give the operators and operator-supporters a break. They don't need to break their backs just to feed their kids! That mentality is nothing more than OLD-SCHOOL GREED!

I tell my operators that the very last thing I want to do is put them out of a job! I tell them that I only want to increase their sleeping time! That, of course, is nothing more than a metaphor indicating that I want to increase the available time that they need to perform their other assigned tasks!

Of course, when it comes to live or die, one tends to choose live.

But then... when and why does it even have to come to that point?

American Indians, of which I am proud to include myself, have always recognized the "Circle-of-Life". We ALL need to work together to make this thing called Life work! FOR ALL OF US!

So... yeah... I can appreciate the objection that was raised with htservices. They apparently don't care about US in general. They only care about themselves, assumming that the ramifications of their actions will be manifested only after they are long gone... after having benefited from their greed.

Damn, this being a caring human-being thing, regarding this particular species, among others, is really tough!
 
thanks for all of your (very quick) responses

to respond to several statements:

to Crocop:
1.) i'd probably start with either Allen Bradley (as they seem to be the biggest company) or Siemens because they sponsored the research of one of my old professors so I know they have a relationship with my school.

to Terry Woods:
2.) why would I want to simulate the inputs? why not buy the actual sensors and use them in real world applications. I could easily come up with projects to utilize mechanical switches, IR sensors, thermal sensors, etc. (in fact, my first project might be a basic "if the temperature in my room exceeds xxx degrees then flip switch to AC unit.")

to elvemike:
3.)"For about 300.00 you can get an Automation Direct DL-06 & programming cable,.."

is this just the cable (physical wires)? or is this a "hand-held programmer" like Terry Woods was talking about?

to everyone:
4.)how do i figure out which CPU to get? I don't need a lot of processing power(speed) or memory. what other parameters are used to catagorize the processor module? Also, do I want DC or AC power supply? I want to be able to just plug it into a standard 120V AC socket.
 
I'm in your boat also. Just trying to learn. Allen Bradley and Siemens seem to be some of the most popular units around here, but most of these guys are full blown professionals. For Joe Blow just trying to learn, I've found that the Automation Direct products are decently priced and more readily obtainable.

I picked up a DL205 PLC on Ebay for a great price. The '205 bases and modules seem to be on Ebay ALL the time. Try to get at least a DL240 CPU, but preferrably the DL250-1 or DL260. There are TONS of
IO modules to choose from.

However, the brick type PLC's would be your best starting point. You can get a basic DL05 for ~$99. http://web1.automationdirect.com/adc/Shopping/Catalog/PLC_Hardware/DirectLogic_05/PLC_Units/D0-05DD

This is one of the most versatile models and allows you to take full advantage of the high speed counter/quadrature encoder inputs and pulse outputs for basic motion control of servos/steppers if you desire in the future. The relay output models are nice as they can switch AC or DC, but you lose the pulse output for motion control with the relay or AC output models. You can always add a relay output or AC output, or more inputs later with the extra IO expansion slot.

The programming cable is like $30 from AD, but can be had on Ebay for ~$10 from a guy that makes them himself.

As mentioned the programming software is free, but limited to 100 words, which is pretty generous for hobby level/self teaching use.

The brick PLC's do have a built in 24VDC PS, but you will need a larger separate 24VDC PS when you start to get any loads over .2A or so. You will also want to pick up a variety of switches and sensors to use for practice inputs.

Good luck.
 
hmm...
It depends, what PLC do you want to use? Siemens, AB, ABB GE... or anything else. Most of companies have "starter kit" in offer. Mostly Starter kit include PLC + software + connection cables.
 
"to elvemike:
3.)"For about 300.00 you can get an Automation Direct DL-06 & programming cable,.."

is this just the cable (physical wires)? or is this a "hand-held programmer" like Terry Woods was talking about?

Forget the HHP for now. The programming cable is for plugging the PLC into your PC. About $30.00. The reason why I would strongly reccomend the DL06 is because it has a FULL instruction set, real time clock and counter module etc.. all on the base unit. All you need would be an analog module and you've got pretty much all the hardware you need to practice most common programing code applications. It's a great learing tool. For the purposes of getting an education on AD products this is the very best choice. The next best choice would be a D2-260, which will cost you twice as much.

When you looking for a PLC for the purposes of education, you want the CPU with the largest instruction set and most versitile I/O, so you can cover all the bases. In the AD line that would be the DL-06DD (DC in/DC out).
 
i'd probably start with either Allen Bradley (as they seem to be the biggest company) or Siemens because they sponsored the research of one of my old professors so I know they have a relationship with my school.

You can do that, but dont discount the growing popularity of AD. It's not a fly by night outfit, and it's very affordable to get into.
 
Tir38...

The reason I suggested the switch/push-button input simulator is because you said...

"I think I can get most of this stuff used on eBay for $100 - $150."

That sounds like you plan to be somewhat frugal in your spending. That is entirely reasonable and sensible.

However, if you plan to buy actual sensors for your inputs... just buying 2 or 3 sensors could very quickly exceed the amount that you already spent for the basics (PLC, cable, etc.).

My point is, in terms of learning, there is no difference between a photo-eye, or a proximity sensor, or a limit switch, or a sonar-ranger, or... and a 49-cent push-button or a 59-cent toggle switch.

You can simulate an analog input signal through a simple 49-cent Pot. You can monitor an analog output through a few $1.50 LED-BarGraphs and a few resistors tied together (kinda crude, but it works for learning).

Actually, you don't need the Pot or the LEDs at all. You can do it all through the status screen.

As you become more serious about this stuff, and possibly begin building what my Dad used to call an "Electric Snake" (nothing more than an automated bells-and-whistles contraption kinda thingee - basically, an automated do-nothing sorta thing) you can certainly spend as much money as your heart desires, and your pocket can support.

I was simply pointing out what would serve as a reasonable minimum for simulating inputs and outputs.

Many of us here at PLCnet that have developed simulators do NOT use actual sensors for test inputs nor actual devices for outputs (except in very special cases). They're expensive and always being cannibalized for emergency repairs. Not to mention that you can crowd a whole bunch of switches and/or push-buttons and indicator lights into a very small area right along side of your keyboard or in front of your PLC... and they won't be cannabalized!

Some of your follow-ups sound like you might be going over-board and jumping into water that is just a bit deeper than you need at this point.

One of the basic tenets of PLC Programming is... if you can program a PLC at all, you can program ANY PLC. The KEY is learning the logic behind process control. That also includes have a sound understanding of the Laws of Physics.

The logic behind process control can be learned on any decent PLC. Actually, you don't need a PLC at all to learn the logic behind process control. You do, however, have to learn and understand "logic". If you don't understand how logic works... even a Billion-Dollar PLC wouldn't be able to help you!

Whatever, it's up to you.
 

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