PlasticsDude

I want to use pulse width modulation to control an electric resistance heater. I've got "real" thermocouple data being fed into memory. How does one generally go about feeding this data into a loop to run a pulsed output? Thanks! (S7-200 CPU 224XP)

On my test bench I have a thermocouple connected to an EM 231. I'm moving data from AIW0 to VW1000, then converting that to a double integer. Then I'm converting to REAL (DI_R) and storing it in VD1504. How do I display the temp data on the PC status screen using Step 7 software? Is this possible? Thanks!

Maybe a very basic question, but when is the use of an interrupt warranted in a PLC? What are the common uses of interrupts? I am guessing that when a "STOP" button is pressed this would normally trigger an interrupt, and the reason for this is so that the entire STOP routine need not be polled every scan, is this correct?

I'd love to see a sample program snippet showing data coming in via an EM231 from a 100 ohm RTD being fed into a control loop which uses pulse width modulation (on/off control) of one of the pulsed outputs to control an electric resistance heater (through SSR's). Does anybody have anything like this? Thanks so much!

So basically using an interrupt to "STOP" a machine would in most cases be complete overkill?

Can I wire a pressure transducer directly into a CPU 224XP or will I need an EM231 module dedicated to this task? Thanks!

But I guess I could just buy a -10V - +10V pressure transducer right?

Relatively speaking. For a 100% newbie, it seems a bit difficult to use. Anyone else agree?

I'm about to start cold turkey with an S7-200 PLC. Does anybody have a link to a *very* simple program showing the basics of ladder logic, for example a momentary "start" button is pressed, then after a preset delay a contact opens, and closes when a momentary "stop" button is pressed? Seeing something like this will lay the groundwork I think. Thanks a whole lot in advance!

What program do most engineers use to make wiring diagrams? Currently I use AutoCAD 2004 which is versatile but you obviously have to "stick build" the entire diagram which is tedious, and being that wiring diagrams are only a small part of my job I need something a *lot* quicker and more automated. Any suggesitions?

Are there any inexpensive PLC's with free software? For example if I get a DL05 for $99 I still have to pay $350 for software...too much!

Turns out I'm getting my hands on a Siemens S7-224 through work. Thanks to all who replied. Wish me luck, I will need it I think! Hope that S7 is a good unit...

What's the part number for the 10 point? I'm bidding on a Micrologix 1000 on ebay right now...

So basically if I get an AB Micrologix 1000 I can download fully functioning free software to train on it? Thanks for any replies.

Does the ML05 have full functioning free software? http://www.automationdirect.com/static/press/dl05_analog.pdf

Does anybody make a cheap ($25) absolute pressure switch? I need something to close a contact at +50mm Hg absolute pressure... I'm guessing the answer is no but thought I'd try...

In our company's current non-PLC based equipment, we apparently use a 5VDC switching/sensing voltage. This requires the use of gold contacts and even with that, it's still not all that reliable. I'm thinking of just using 120VAC on a new PLC based system. This would also eliminate the need for a rectifier (DC power cube). Does anybody out there use 120VAC in their cabinets or is this considered too hazardous to operators and service people? Regardless, we have 230VAC, 400VAC, 480VAC, and 575VAC in our cabinets for the motors and heaters...

How much did the average PLC cost in the 70's, 80's, 90's and early 2000's? Very curious about this. Some old timers could definitely answer this! Thanks.

I'm thinking about buying a PLC and hooking up some toggle switches to the inputs and LED's to the outputs and just playing with it at home to see if I can learn how to program them...just use the toggles to simulate sensors and the LED's to simulate relay outputs. What would be a good cheap unit to buy as a leaner?

Can I wire an RTD and a pressure transducer directly into a Micrologix 1200 and read them directly, with no other hardware? Thanks for any replies in advance! What does this unit go for approximately?

What's the point of the analog inputs then? I don't understand. What does the module do? Thanks!

What about this one?: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewI...p;rd=1&rd=1

I'm 100% new to PLC's and luckily am starting with a very simple project. I have a machine that has a blower, an electric resistance heater, and a vacuum vessel. I need to be able to turn the blower on/off, control the air temperature (SSR time proportioning), and turn a vac generator on/off and monitor vessel pressure. Other than a PLC itself, what would I need to do this? Would it be cheaper to use a stand alone P-I-D to control temperature, or can a PLC accept a 100 ohm RTD input? Thanks so much for any help!

Thanks to all for the replies. It looks like I really have my work cut out for me, probably more work than I thought. If it weren't for the RTD and the pressure transducer inputs maybe it wouldn't be all that bad. How long does it usually take to get up and running with PLC coding from the ground up? I really need to get my hands on one and just see if I can even make an LED light up of something...to start.

Anybody have some good book ideas for learning ladder logic starting from the ground up? Thanks!