Calculate Speed Using Prox

Hi,

I am looking for a little help. I currently have an old Telemecanique TSx 17 that I need to replace. I am looking at installing an AB micrologix 1500. My question. I have a prox that detects roller shafts on a continuous chain. The chain has speed control with an old Lenze DC drive. The prox goes to the event input on the Telemecanique PLC an through PLC logic determines units/min and units/hour. How could I best accomplish this in the micrologix.

Any help would be greatly appreicated.

Kind Regards,
Heliman.

First of all - I would use a MicroLogix 1100 so you can have online programming and Ethernet. How many shafts per minute maximum will the proxy see?

Hello Heliman

Welcome to your first post.

very simple.
You need to connect the prox to the high speed counter on the ML.
You need to count the number of pulses for certain time ,lets say 10 sec.
after that time move the value to another register let say N7:0 and reset the counter,and start again.
Multiply the N7:0 by 6 and you have the result (per Min).
If the no of pulses is not high,about 30-35 per sec,you can use regular counter.

If you have more questions feel free to ask.

best lack.

Bluenoser, Good point on the 1100, I will look at that. The Max pulses the prox will see per minute is base on the speed, this is continous motion. Average speed is around 25 per minute.

ArikBy, I will try that.

Thank you for the replies!!

Heliman...at 25 per minute, you can use any of the digital inputs for your proxy connection. ArikBy is right on with the calculation method. Good luck!

PS - Make sure your proxy delivers what the input requires (+ or - signal).

With 25 pulses per Min ,use count time as 1 Min.
If you use 10 sec you might not be accurate.
ML 1100/1400 better then ML1500

Another approach

Another approach which will give you quicker results when
you have a low pulse rate is to check the amount of time
between rising pulse edges.

You can calculate results on every rising pulse based on
the between pulse time.

For example, if the time between the rising edge of 2 pulses
is, say, 83ms then you will have (1000ms * 60 seconds)/83 ms
pulses per minute. I think you can take it from here.

You do have to take care of the end condition; when the motor
stops and there are no pulses for a period of time. Regardless,
I like the benefit of not having to wait a whole minute to get
accurate results.

Good Luck

(8{)} .)
(Yosi - remember me?)