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Author Topic: AC Servo Load/Torque VU Meter?  (Read 1330 times)

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AC Servo Load/Torque VU Meter?
« on: January 14, 2018, 07:28:35 AM »
Hi all im trying to make a 10 segment LED VU meter that will output the min and max torque from this servo motor, this will be a spindle load meter for my CNC Lathe, i have searched around but cannot seem to find a noob friendly tutorial about interfacing arduino or some other chip with an AC servo drive, the drive has Quadrature encoder Signals A B and Z out from the encoder of the motor it also has an analog speed and torque output, is there anyway i can make this output as a bar display, i want this to run on an arduino nano v3.0 if there is enough pins if not then it can be a larger one or some other chip, i was maybe thinking some kind of LM series driver for the display which i have uploaded a pic of the ones im using also added schematics of servo drive outputs, any help would be very much appreciated as i haven't a clue where to start with coding im good with circuits though, Cheers.  ;D
Re: AC Servo Load/Torque VU Meter?
« Reply #1 on: January 14, 2018, 07:36:06 AM »
It looks like pin 36 and 17 will give you an analog output signal of the drives torque. You should be able to connect it to the analog input of an arduino then do some code to get it to run the bar graph.

You will need to do some arduino research to do the rest.

Mike
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.
Re: AC Servo Load/Torque VU Meter?
« Reply #2 on: January 14, 2018, 07:52:55 AM »
Okay cool so would this involve the arduino converting this analog signal to something the LM driver can understand such as a linear scale, i know they have a set of voltage comparators in the chip, im guessing it should be quite a simple job however the other 2 servos i have dont have a torque output monitor - would it be possible to take advantage of the encoder outputs or maybe compare the speed analog output to actual commanded rotation speed to come up with a visual load representation? Thanks   ;D
Re: AC Servo Load/Torque VU Meter?
« Reply #3 on: January 14, 2018, 09:26:46 AM »
According to the schematics you posted you have a torque output monitor. Thats why I said pins 36 and 17.

Post a link to the actual drive that you are using and to the manual as well and I will take a look.

Mike

We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.
Re: AC Servo Load/Torque VU Meter?
« Reply #4 on: January 14, 2018, 10:45:40 AM »
Here you go i have attached the manuals, i have a 750w panasonic motor and drive which the MINAS X manual is for, the other two motors are 1.2KW and 3.8KW made by some chinese manufacturer Yifeng or KRS i think? Ill post you a wiring schematic as its all i could find and a link to the ebay page where i bought them, and thanks alot for helping me out ;D

Link to ebay page:-   https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F112411229621

Items are 110st-m04030   and  130st-m15025

Edit:- im also looking for a way to use the speed analog out to write RPM to a 4 digit 7 segment display, i have a couple MAX 7219 drivers knocking around would this just be a case of the arduino measuring either the analog speed ref or the 1ppr Z phase from the quad encoder and displaying on the driver? This is only for the 3.8kw motor as that gonna be my spindle, cheers.
« Last Edit: January 14, 2018, 10:51:29 AM by ElectronicsPnoob123 »
Re: AC Servo Load/Torque VU Meter?
« Reply #5 on: January 14, 2018, 03:27:57 PM »
Hi,
given that servo torque is proportional to current you could pass one lead of the servo output through a Hall effect
current sensor, if you wished for a standalone or analogue solution.

Craig
My wife left with my best friend...
     and I miss him!
Re: AC Servo Load/Torque VU Meter?
« Reply #6 on: January 14, 2018, 03:34:54 PM »
Do they work without contact to the conductor? This motor will pull 70A when on full load?


Edit:- can the entire motor cables be put through something like i have attached below?
« Last Edit: January 14, 2018, 03:42:04 PM by ElectronicsPnoob123 »
Re: AC Servo Load/Torque VU Meter?
« Reply #7 on: January 14, 2018, 03:44:21 PM »
Hi,
yes they do.

This is the sort of thing I had in mind:
http://nz.element14.com/honeywell/csnp661/current-transducer/dp/7234752

I see you want to have speed of your spindle, why?. If you are running it Step/Dir which is pretty much what you
have paid all the extra for then you know the speed...Mach sets it and if the spindle differs greater than the 'following
window' error it will fault 'following error'. Note also that if you wish, even if its redundant, that you can have Mach
monitor the index pulse and have it calculate the actual spindle rpm very accurately and is displayed on screen.

Craig
My wife left with my best friend...
     and I miss him!
Re: AC Servo Load/Torque VU Meter?
« Reply #8 on: January 14, 2018, 03:45:58 PM »
Hi,
yes thats ideal. Note that you pass only one of the three wires through it. If you put all three the currents all cancel
out and the measured current would be zero.

Craig
My wife left with my best friend...
     and I miss him!
Re: AC Servo Load/Torque VU Meter?
« Reply #9 on: January 14, 2018, 04:01:58 PM »
Ok no problem, this is for the manual interface i want to use a variety of opto components such as 7 seg diplays bubble displays bargraphs etc due to aesthetics the machine is going to have a small touchscreen i would like an easy view of the position speed and load  ;D