Student Needs Help

Ok my teacher isn't exactly the greatest but a decent guy.

I need to convert temperatures from Celsius to Fahrenheit using a Micrologix 1400(rslogic500)

I haven't a clue how to proceed so some guidance would be great.

Probably stat from the formula for conversion.
Even in google. As it is simple equation, add, mul and div instructions will do. If you try it by yourself you could learn it.

You can use the Compute (CPT) instruction to do the calculation, or you could use some intermediate memory registers to store each step of the calculation.

As suggested, the basic relationship between Celsius and Fahrenheit is the first step. This is a very simple equation and I'm going to insist that you use a reference manual or even Google to find it.

After finding the temperature conversion equation, the next question is: How will you get the Celius temperature into your MicroLogix 1400 PLC?

What temperature sensing device do you have available to use? Thermocouple, thermistor, RTD, or a temperature switch input?

Is the problem really to use an equation to convert the temperature (a 5th grade science problem) or does it say "configure your MicroLogix 1400 to read degrees C instead of degrees F"? That is a different problem entirely and means you have to learn how to configure the analog inputs to read different parameters.

got it last night.

Easier than I thought it would be.

Did the *5 with my input with a destination

Then used a \9 for that value with a destination.

Worked pretty well. Thanks for the help

VictorBit said:

http://lmgtfy.com/?q=celsius+to+fahrenheit+formula

Click to expand...

I know what the formula is, what I didn't know how to do is get the PLC to calculate it in real time for me.

Thanks for your completely useless answer.

Did the *5 with my input with a destination

Then used a \9 for that value with a destination.

Click to expand...

What about the constant "32"? Where did you put that in you math equation? Also, no one can give you a complete method without knowing the address of your temperature input. Knowing that, it would be possible to give you the conversion steps.

Gossamer69 said:

I know what the formula is, what I didn't know how to do is get the PLC to calculate it in real time for me.

Thanks for your completely useless answer.

Click to expand...

My answer were as good as your question,

"I haven't a clue how to proceed so some guidance would be great.".

victorbit said:

my answer were as good as your question,

"i haven't a clue how to proceed so some guidance would be great.".

Click to expand...

+1

Gossamer69, I think when you posted "I haven't a clue how to proceed" that many of us concluded that you really didn't know the basic "9/5 + 32" conversion between Celsius to Fahrenheit degrees, and that showed an astonishing lack of effort.

We really do see those kind of questions here.

This is actually a really good basic PLC programming question because it brings up unit conversions, rounding, data types, and how data is stored in between operations.

This would be done differently in a Siemens controller or a Koyo controller than it would be in Allen-Bradley, because of the different math instructions and data type conversions.

You'll find that your method of using two intermediate 'destination' memory registers is a very common technique used in all sorts of simple and complex calculations in the Allen-Bradley controller world. It's a good technique to understand.

Now you have the C -> F conversion in your back pocket for the next time you do a changeable-units HMI application.

Condescending comments aside, it is true that this is a good excercise. I'm glad we are seeing students coming here for guidance but please guys, every answer is only as good and precise as the question that was asked. If you feel OP wasn't clear enough for you to provide guidance, don't condescend him. Likewise, OP, if you didn't get the answer you were expecting or you needed, reiterate with more details.

In the US, the C/F conversion formula is taught in the 5th grade - no condescending needed. At least it used to be back in the old days. Now with the Fed's in charge of education, it could be that is not true. Probably by now it is a college-level calculation.

Lancie1 said:

In the US, the C/F conversion formula is taught in the 5th grade - no condescending needed. At least it used to be back in the old days. Now with the Fed's in charge of education, it could be that is not true. Probably by now it is a college-level calculation.

Click to expand...

Now it's just another button on your calculator/phone.

Christoff84 said:

Now it's just another button on your calculator/phone.

Click to expand...

dat app!