Calculate the velocity of motors DC with 1746 HSCE

zaranet

Member
Join Date
Apr 2009
Location
Marrakech
Posts
15
Hi,
I wante to write a program in rslogix500 permet to calculate the velocity of motor DC with 1746 HSCE that i have un encoder accoupled in this motor.
I need your help
excuse me for my english.
 
You speak English better than I speak your native language for sure so no need to apologize.

OK so what I understand is you have
a DC motor
encoder on motor to detect RPM
AB PLC type unknown
AB card 1746 HSCE to handle the encoder output and "translate" this to an output value or to a display screen.

Are you merely going to monitor motor RPM or are you going to control it?
What are you going to use to control DC motor speed solid state controller or?

More information on machine will be helpful ie what machine does motor speed HP etc.
Dan Bentler
 
I want to control my motor, if it superior than valeu limit of velocity that in my program i compared the velocity of motor with my reference; So i diminute it by injecting the resistor
AB PLC type SLC500/04
 
What units do you want for your velocity? RPM? cm/sec? etc...

Tell us about your encoder. How many pulses? etc.

If you're looking for a distance/time, then we'll need to know some distance:encoder relationship information, too.
 
QUOTE I want to control my motor, if it superior than valeu limit of velocity that in my program i compared the velocity of motor with my reference; So i diminute it by injecting the resistor AB PLC type SLC500/04 UNQUOTE

OK so what I understand is you have
a DC motor
encoder on motor to detect RPM
AB PLC type unknown -- AB PLC type SLC500/04
AB card 1746 HSCE to handle the encoder output and "translate" this to an output value or to a display screen.

I assume you have a shunt DC motor and you are going to use PLC and encoder to have the PLC control speed by controlling a resistor in series with shunt field.
Is this a variable resistance ie reostat
or is it a single resistor with a bypass contact or multiple resistor and bypass contacts?

Dan Bentler
 
To respond to your first question about calculating the velocity of the motor, are you able to read velocity with the 1746-HSCE card? If you need help configuring the card, then look at the rate mode example in the manual.
 
can you give me an exemple the program permet me to calculate the velocity

can i use the rate period for calculate this velocity???? then numbre the tour/valeu rate periode
 
Maybe I got ahead of myself. I forgot you can get the current count and velocity from these cards. You can just set up the configuration file for count mode. Then the current encoder count is available in address I:e.1 (where 'e' is the slot number of the HSCE card). The current encoder rate is available in address I:e.3 (again, were 'e' is the slot number of the HSCE card). Take this value and divide it by the scale factor where your scale factor is the number of counts per measurement unit. The result is your rate or velocity in measurement units per second.

So, follow the manual to setup the configuration file (the integer file) that is moved to the M file (i.e. COP #N7:0 #M0:e.0 42). Enable the counter (M0:e.1/12) and then read the rate address. The first example in the manual is simpler and perhaps easier to understand.
 
I think you need to look at a couple questions first
1. Is this machine already running or are you putting it together?
IF runnning
2. Are you able to control motor speed now even if only manually.
3. how are you controlling speed
4. Do you have a mechanical tach to measure motor shaft RPM?
5. how many pulses per revolution on the encoder
Dan Bentler
 
i configure my cards HSCE then i devide word I:e.3 by the word I:e.2 to have the velocity of motor
I:e.2 indicates the number of counts obtained during the last Rate Measurement Period.
is it right???
 
I configure my cards HSCE, i use rate mode and linear counter, i use the accumulated counter in word I:e.1 but i don't know how can i use the velocity by this card
after you the expression's velocity is I:e.3/I:e.2
with I:e.2 indicates the number of counts abtainedduring the last rate measurement period
is it right?????
 
"...velocity is I:e.3/I:e.2...is it right?" No.
The rate or velocity is the value in I:e.3 and only I:e.3 as I mentioned in my previous post.

Now if you want to convert it to engineering units "tr/sec" then you need to calculate how many counts of the encoder there are per "tr". I do not know what a "tr" is. To calculate this you need to know the number of encoder counts per revolution of the motor. You also need to know the number of "tr" per revolution of the motor. Then you take "tr" per motor revolution and divide that by the number of counts per motor revolution to get your scale factor, which is a constant. (Note, there are other ways to calculate this. You can look at the number of counts per encoder revolution, the number of motor revolutions per encoder, and the number of "tr" per motor revolution.)

Once you calculate this scale factor, you can calculate in the PLC the velocity in units of "tr/sec". You would do this by taking the value of I:e.3 and dividing it by your scale factor.

So, what does your "tr" represent? I am not familiar with this unit.
What slot is your 1746-HSCE in?
 
my encoder is accoupled a motor so the number the number the tr of encoder equal to number the tr of motor
the number of encoder counts per revolution is 1250 so my velocity in units of tr/sec is I:e.3/1250
slot the my card is 2
 
So, when you give your motor one revolution, does the contents of I:2.1 (the counts) divided by 1250 correctly should the number of "tr" it has changed?

I still do not know what you mean by "tr".
 

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