RPM Count by a proximity sensor

 Hi William,

First of all thank you for you help.

It's first time working with S7 1200, I have small experience in s7 300,(start/stop of small installations, a couple of sensors for logically control) LAD or FBD languages programming, so I don't have so much knowledge's, but I am willing to learn.

I have created a pdf which contains: overall diagram, sensor & cpu datasheet and function for length measurement, which I tested and it's works, assume it was easier to do it with HSC but I don't know how.

Also I don't know what is the maximum switching frequency of  DI (PLC input) , at what speed I need to buy a dedicated modul of HSC, ussualy for every drum I have gear house(ussualy maxim rotation speed normaly is around 30-35 meters per minute, I need dedicated module for this speed/length measurement ?)

I am stucked at this part of speed measurement I don't know how to do it.

William_B

bogdan.juninho

sensor 150 Hz

Hi.

The mentioned specification worries me...
what do you mean by this?

Sorry for asking: Could you make a photo of your hand drawing showing where each component (motor, gear and sensor) is in relation to one another?

The CPU you mention - what firmware version is it?

To get a feel for where we are starting from.... what (more-or-less) do you know of the S7-1200 and the programming of it? ..for example: which coding language do you prefer?

Thanks for your patience.

i am sorry that i did not have a s7-1200 CPU in the office to simulate a sample program and with the PLC-Simulator you cant simulate a HSC. 

Okay.First of let us make a conclusion :

You want to calculate the RPM of the motor and the length (you did not mention of what ) from an inductive proximity switch which you put it infront od the teeth of the gear box. 

1. you did not need a two Proximity switches for that, one is enough.

2.you should activate an HSC in the CPU configuration and configure it like what been said before.

3.the maximum switching frequency for your the S7-1212 CPU is 100kHz and that is enough for your purpose.

4. Williams_B gave us a TIP to use the instruction CTRL_HSC_EXT to calculate the number of pulses in the HSC with predefined period. you can easily find it in the insruction list under Technology--->Counting. then open the help for the instruction by presing F1 and have a look. 

5. (EdgeCount*MesurementFaktor)/Periodtime is your rotaional speed. 

6. to calculate the length you can easily monitor the ID1000 and multibly it with your mesurements factor.

 Hi OpisOm,

Thanks you for your patience and your help.

Thanks for the advices for sensors and the maximum switching frequency for your the S7-1212 CPU.

The length of a chain, I want to monitor, I 've maked with HSC and it's working with ID1000.

But still something on speed (EdgeCount*MesurementFaktor)/Periodtime I am doing wrong, please see the pdf from attach.

Thank you in advance!

OpisOm

i am sorry that i did not have a s7-1200 CPU in the office to simulate a sample program and with the PLC-Simulator you cant simulate a HSC. 

Okay.First of let us make a conclusion :

You want to calculate the RPM of the motor and the length (you did not mention of what ) from an inductive proximity switch which you put it infront od the teeth of the gear box. 

1. you did not need a two Proximity switches for that, one is enough.

2.you should activate an HSC in the CPU configuration and configure it like what been said before.

3.the maximum switching frequency for your the S7-1212 CPU is 100kHz and that is enough for your purpose.

4. Williams_B gave us a TIP to use the instruction CTRL_HSC_EXT to calculate the number of pulses in the HSC with predefined period. you can easily find it in the insruction list under Technology--->Counting. then open the help for the instruction by presing F1 and have a look. 

5. (EdgeCount*MesurementFaktor)/Periodtime is your rotaional speed. 

6. to calculate the length you can easily monitor the ID1000 and multibly it with your mesurements factor.

hello, 

let us make it much more easy without using the function CTRL_HSC_EXT :

like what befor said :

in the ID1000 you find the numbers of the all incomming pulses use the Cyclic_Interrupt to calculate your speed. as example each 1000ms make a cyclic interrupt and there subtract the previous value of the ID1000 from the new value. 

i have made a small code may it helps 

 Hello,

Do I need to do something else beyond adding new ob 30, because my system is not cycle interrupting it remains unmodified.

Please see attach!

OpisOm

hello, 

let us make it much more easy without using the function CTRL_HSC_EXT :

like what befor said :

in the ID1000 you find the numbers of the all incomming pulses use the Cyclic_Interrupt to calculate your speed. as example each 1000ms make a cyclic interrupt and there subtract the previous value of the ID1000 from the new value. 

i have made a small code may it helps 

in your second network the Tag should be MD210 not MD201  becouse it overlabs the tag MD200 as New_HSC_Read.

what is the time value have you enterd in the Cyclic Interrupt ? for 1 second monitoring should be 1000ms.

 Dear OpisOm,

You were right about MD210, now it seems that the cycle is interrupting after 1000 ms.

According to drum specification, the speed on the gear is around 15 meter/min.

15 m ...........60 sec

x m..............1 sec result  that x =  0.25 meter/ per sec

According to calculation my MD214 is 2.4 meter per minute.

I have divided already to number of teeth which is 25.

I also put this formula :

V(md212)= PI * Diam_drum * n (md214) / 1000 where:

      diameter of drum is 800 mm

n= v * 1000 /pi * D

n= 0.398 * V result according to calculation my MD214 is 23.8 meter per minute.

   I have one impulse per second made by the sensor.

    Please see the pdf from attach, first two pages are according with formula divided with 25 teeth.

   The third one is contain the formula written up.

Where I am doing wrong?it seems the velocity from drum specification is not the same with the calculated one.

Thank you in advance!

OpisOm

in your second network the Tag should be MD210 not MD201  becouse it overlabs the tag MD200 as New_HSC_Read.

what is the time value have you enterd in the Cyclic Interrupt ? for 1 second monitoring should be 1000ms.

Hi

ref

this is why I am using data blocks for global values - it can be nicely structured and compiler take care of addresses - no overlaps any more.

I use Ms for testing only.

then when testing done do a cross-reference for Ms and delete them.

You have made the same fault MD212 is a double integer and allocate 4 bytes in the memory:

MD210 is : MB 210  MB 211 MB 212 MB 213

the next free area willl start with MB214 so in your program make a revision to the all tags you have defined and do not over lab any tag. 

as example :

MD210 :Speed_Sec

MD214 :speed min 

MD218: rotation min 

MD222 :xxxx