dual compressor bcd display help !!!

[erdidi]

hi everyone i'm new to plc and i real don't understand much but i realy need to do this when air pressure reached the pe2 value i have to shutdown both compressor after that i have to write to reacehed pressure to bcd dislplay can anyone tell me how to do this ?

 

[RussB]

hi everyone i'm new to plc and i real don't understand much but i realy need to do this when air pressure reached the pe2 value i have to shutdown both compressor after that i have to write to reacehed pressure to bcd dislplay can anyone tell me how to do this ?

I am sure that lots of people could tell you how to do that if they had more detail on the hardware and other devices in your system.
If you need to specify, install and program the controls to do this may I suggest that you hire a local electrical contractor with industrial control expierence.

 

[Lancie1]

I would bet US $1 that Erdidi is using the LogixPro Simulator software and is working on the Dual Compressor Student Exercise #4

Exercise #4 --- Detecting When 1 Compressor is not Enough
When the plant's requirement for air closely matches the maximum volume that can be supplied by a single compressor, our current control solution simply falls apart. It's possible that this single compressor could run for hours without ever being noticed, nor obtaining any down time in which to cool. How long one of these compressors might be allowed to run continuously would normally be specified by the manufacturer, but for our purposes we will just ensure that excessive run-on can simply not occur.

When attempting a solution for this run-on problem, a couple of ideas may come to mind. If a single compressor runs beyond the time that would normally suffice to attain full pressure at 50% or 60% flow, the idle compressor could be started to assist in the effort. A second method might be to track the time it takes for the pressure tank to drop from it's maximum to minimum settings, and from this determine beforehand whether 1 or 2 compressors need to be employed.

If given some thought, you may detect minor faults with either of the above methods. The first method could permit repeated short cycling of the back up compressor when operating at certain continuous flow rates. The second method attempts to anticipate load demand, but may not accommodate rapid changes in plant air utilization. It may be that your solution should combine both methods, or possibly a new one not even discussed. Your goal should be to analyze the system and come up with the best solution possible using the available equipment.

Modify your program so that continuous run-on of a single compressor will not occur. Your solution should continue to alternate between compressors when plant flow rates are typically 50% to 60% or lower. In addition, try to equalize wear on each compressor, and avoid short cycling as much as practically possible.
Continue to utilize PE2 to detect if the system pressure descends below the prescribed minimum, but feel free to tune or adjust both this pressure switch and any timing mechanisms employed in order to attain the best possible performance.
In order to monitor how well your system is working, provide a means to display the accumulated run-time for each compressor. Utilize both the panel mounted selector switch, and LEDs for this purpose.

Once you have your program tuned to perfection, you should have a good grounding in the basics of controlling many types of similar systems. It's fairly common to find fans, or pumps etc. being controlled in a similar fashion, and the techniques you've developed here should closely apply.

Here are the solution steps to display the compressor running times:
1. Create a subroutine U3 "Run-Time Display".
2. Use a RTO Retentive Timer On to accumulate the running time for Compressor 1. Because the timer measures 0.1 seconds, divide the ACCumulator value by 10 to find running time in seconds. Put the result in a N7:x memory location
3. Do steps 1 and 2 for Compressor 2.
4. When Selector Switch Position "A" is ON, use a TOD to convert the N7 value to BVD format for Compressor 1. The Dest address must be Output O:4
5. When Selector Switch Position "B" is ON, use a TOD to convert the N7 value to BVD format for Compressor 2. The Dest address must be Output O:4
6. When Selector Switch Position "C" is ON, use a ADD to add the N7 values for Compressors 1 and 2, and then a TOD to convert the total to BVD format for both Compressors. The Dest address must be Output O:4
7. If either timer reaches its maximum value of 32767, or during the S:1/15 First Scan, reset both RTO accumulated-run timers.

 

[erdidi]

congratulations you have won half a dollar yes i'm working whit dual compressor on logixpro but it is for a project i got from school and thank you

 

[Lancie1]

I think your problem has been slightly changed, and asks for the accumulated pressure instead of the accumulated run time. However you can sort of calculate the pressure as a function of the accumulated run time.

With the air use "% Flow" set to 0, Pressure = 0.2135 x Accumulated Run Time (0.1 second time base). If you have to set the % Flow to >0, then you will have to adjust the multiplier downward to offset the air being used.

Becasuse in the early PLCs such as the Allen Bradley SLC 5/02 (which LogixPro simulates) there are only integer numbers, you have to multiply by 21, then divide by 99 to get an approximation of the 0.2135 multiplier.

 

[Lancie1]

You will find many versions of the LogixPro Dual Compressor student problem on PLCtalk's Download section:

http://www.plcs.net/downloads/index...ey&PHPSESSID=25f7f1c8a128ce26ddbef768f8806e5d