Calculate percentage of last 500 parts.
- Thread starter roskel
- Start date
Clay B.
Lifetime Supporting Member
Is this to be a "rolling average" or every 500 parts you need a percentage?
Clay B.
Lifetime Supporting Member
Well I would create a FIFO that contains 500 data points. Each Data point will be a value of 1 if the part is good or 0 if the part is bad.
Each time you check a part as good or bad you would then take your 500 data point FIFO sum its data and divide by 500.
Now you have a rolling average.
One warning, when you do your divide function you should put a greater than zero condition. PLC's do not like to devide into zero, this usually causes a math error.
Each time you check a part as good or bad you would then take your 500 data point FIFO sum its data and divide by 500.
Now you have a rolling average.
One warning, when you do your divide function you should put a greater than zero condition. PLC's do not like to devide into zero, this usually causes a math error.
TConnolly
Lifetime Supporting Member
A SLC will only allow 128 elements in a FIFO. Extending the FIFO across files could get hairy. You could use a 500 bit shift register (BSL instruction) where a set bit represents bad parts. Then keep a running sum of the bits. Don't count bits. When a 1 is shifted in then increment a counter and decrement it when a 1 is shifted out.
See attached. It needs some spit and polish but hopefully it will get you started.
See attached. It needs some spit and polish but hopefully it will get you started.
Last edited:
Clay B.
Lifetime Supporting Member
A SLC will only allow 128 elements in a FIFO. Extending the FIFO across files could get hairy. quote]
Forgot about that... but I have an answer. You can roll your own FIFO. I hve attached a program where I built one a few years back. If you look in ladder 10 the FIFO starts on rung 16 and goes thru rung 25.
The GRT that starts the FIFO is only true for 1 scan. This is important to prevent double coping of data.
Since I am doing a copy function 10 words in length I use 1000 words in my data table. Since you can only put 250 intergers to a data file I had to use 4 data files.
The only limitation to this roll your own FIFO is memory space.
Note: this is just another option. I believe Alaric's solution is easier to do and does not require near as much code. (I have it in my sample library now).
Similar Topics
Hi everyone,
This is my first time posting, so please forgive any omissions or mistakes.
I am attempting to control the velocity of a stepper...
Good morning,
I have a question. I don't know much about ST yet
I would like to calculate the average number of products per hour.
how do I do...
Can someone help me with this?
I'm no good at SCL - virtually everything I've done so far has been ladder logic.
The return value from the...
I want to calculate the energy consumed from instantaneous power. Can this be done using the TOT block with timebase set to Hour?
Hi everyone,
I have to calculate the length in millimeters of a glass that enters a transport (I don't know the speed yet) through a barrier...