Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: DeanoM on December 17, 2012, 08:33:55 AM
-
i have an invertor that has a rs485? output. seems to just be 2 wire termainals.
is there a way i can feed back the amps/load to mach3?
-
What inverter is it?
It can be done, however without knowing what inverter you have, nobody can really tell you.
Provided the inverter can output the required information via RS485 (aka Modbus), and you have an adapter to connect RS485 to your computer, it is doable.
-
As and option most VFD have a removeable display /programming panel. With a simple extention cable you can move it over to your control display. I did mine that way years ago in lue of fiddling with modbus/rs485/rs232
Just a thought, (;-) TP
-
have atached the io page. may tell you more about the rs485. nowhere in the manual does it talk about the output or give any info about this output at all. i assume there is some other programming manual that i just don't have.
the invertor is a vp10 vacon unit
-
I'm not sure if I've got the manual for the same VFD, but according to this manual (http://www.vacon.com/ImageVaultFiles/id_2862/cf_2/Vacon-10-User-Manual-DPD00717C2-EN.PDF) all the information you want is available via Modbus.
-
wow thanks. that would have been a great help when i was trying to sort these out when i got them.
cheers.
-
OK, I am looking into getting a FR-D700 Mitsubishi VFD, the BOB is already set up so one RJ45 cable does it all, analog of course. Is there an advantage if I try Modbus? What is most important to me is a spindle load meter displayed in mach. I am clueless as to how to go about that. I have a very meager understandging of modbus after reading up a bit on the topic.
-
OK, I am looking into getting a FR-D700 Mitsubishi VFD, the BOB is already set up so one RJ45 cable does it all, analog of course. Is there an advantage if I try Modbus? What is most important to me is a spindle load meter displayed in mach. I am clueless as to how to go about that. I have a very meager understandging of modbus after reading up a bit on the topic.
The problem with using analog is that you need an analog input to the computer. Using Modbus brings the info in without the need for an analog input. Many converters allow you to bring in a fair amount of info via Modbus.
Mike
-
OK, I am looking into getting a FR-D700 Mitsubishi VFD, the BOB is already set up so one RJ45 cable does it all, analog of course. Is there an advantage if I try Modbus? What is most important to me is a spindle load meter displayed in mach. I am clueless as to how to go about that. I have a very meager understandging of modbus after reading up a bit on the topic.
Are you talking hardware converter or computer language converter. If you talking hardware converter, thats the easiest part of teh whole deal. I don't understand how to write p[ackets and all that. How do I communicate speed control via modbus for example, that is not digital yes or no signal.
The problem with using analog is that you need an analog input to the computer. Using Modbus brings the info in without the need for an analog input. Many converters allow you to bring in a fair amount of info via Modbus.
Mike
-
I'm curious what you plan to do with spindle load feedback. Mach3 can't really make use of it to do much useful, other than display it. An analog ammeter connected to the motor would seem a more useful tool to me....
Regards,
Ray L.
-
For starters, when spindle load gets to be above .9 have mach feed hold and stop ( basically a brain that see's a certain parameter above a certain value and does a 1001). This would save a lot of hassle down the road. When I get to .8 its time to resharpen and it will also tell me if my feed is too low or too high when I start out with a new end mill.
-
You'd have to do a lot more than just read load to do that reliably, as you WILL see momentary loads that go well over 100% (for instance, when you enter a corner), and you don't want to trip on those. Plus, the readings you get will typically be VERY noisy. At a minimum, you'd need to do considerable digital filtering, just to get something stable enough to work with. I don't see how you'd do that in a brain. Possibly a macro-pump.
Regards,
Ray L.
-
How can a modbus packet be noisy? OK, so there would have to be a rule about 100% spindle load for no more than .75 second or some other number. why woudl I need a macro instead of a barin. its a simple rule of if input> X and for longer than Y time period do 1001.
What's digital filtering?
-
The VFD may well be sending raw, instantaneous current readings. If so, the readings you receive will not be steady, but will have quite a bit of variation from one reading to the next, and their values may well exceed 100% load at times, as most VFDs allow short-term overloads of as much as 200%. To make them usable, it may be necessary to filter them using a digital filter, which is a software algorithm that that performs exactly the same function as an analog filter (resistors and capacitors), but all the processing is done on digital values, rather than analog voltages.
If I were doing it, Id make use of the current limit feature that is almost certainly built into the VFD, and take the VFD ERROR signal, and run that into Mach. Then, when you over-load the machine the VFD will shut down, and you will simultaneously get an ERROR signal from the VFD you can use to shut down Mach3. I think you'd find that would work much more reliably, with much less tweaking and tuning.
Regards,
Ray L.
-
OK, chalk one up for doing it the old fashioned way. Do you know of a good analog or digital meter that I can hook up to the analog output of teh VFD to show me load? Kinda like what tormach has. I guess that acording to what you say, I shoudl just set a relay to go off at a prescribed limit and chain that to spindle fault input in my MACH.
-
How about hooking uyp one of these to teh nalog output of the VFD? http://www.mpja.com/download/8054me.pdf It's rated for 20VDC but, I can use a 5vdc power source to calibrate teh reading to show 50, put the decimal in teh 3rd position and that should be it. I will have teh VFD output 10VDC on teh analog output and these is my load meter.
-
Putting a voltmeter on the VFD will tell you nothing of value. You need to be looking at current, which means putting an ammeter *in series* with one phase of the motor. The Tormach load meter is nothing but an analog ammeter. An analog ammeter contains a shunt, which is a very small, precisely known resistance. When current passes through it, it creates a small voltage drop (typically 50mV at maximum allowed current), and the meter itself is a very sensitive voltmeter, connected across the shunt, that reads full-scale with 50mV across it. Look at digikey, mouser, and other electroincs supply houses, and find one with a suitable full-scale reading. But, a good analog ammeter will not be cheap. However, a digital meter, in this application, would be completely useless.
Regards,
Ray L.
-
If the tormach load meter is just an ammeter, then why do the instructions for installation call for changing parameters in teh VFD?
-
I am not sure about VFD's but servo drives often have an analogue output that you can set up to be used for different things. I have mine set up on the big lathe to look at spindle current and I have it scaled in the servo drives setup such that 10v is 150% of continuous rated current of the motor thus I have 0-150% load meter. I used an analogue ammeter with centre zero and made a scale up for it to represent 150% - 0 -150% and it works great, I used a fixed resistor and a trimpot to allow me to adjust it slightly to get true zero. I will take a pic later to show it. Oh and the reason I have the centre zero is the analogue out from my servo is +/- 10v rather than just 0-10v so if the spindle is M4 it will show deflection as the opposite way.
Hood
-
There are a number of reasons to present a spindle load signal to MACH.
I tend to agree that if the only use will be a readout, then it would be a lot easier to just put an ammeter on the motor (as already described) or use the remote VDF panel (also as already described). However, there are lots of reasons that it would be useful to have the spindle load presented to MACH (by whatever means the user chooses).
However, as can be seen from Hood's posting, the uses for having torque data are only limited by the users creativity and cleverness.
I also have plans to rout the torque output analog signal on the spindle drive to MACH for the purpose of a read out certainly, but also to monitor loads as desribed ealier.
The momentary overloads are easily accomodated with a timer as descibed in a previous post. That is not really different from the normal faulting process in the drives from follow error, overload, overheat, or a host of other maladies. However to take it a step further, you can have MACH slow the feedrate if the load exceeds a certain amount, or at least provoide a warning that something, a dull tool perhaps, needs operator attention. If a user has industrial drives (like Hood is referring to) you can take the load info and feed back to the drive whatever corrective action you think is appropriate.
A project on my to-do list, just be way of example, it to limit the torque output of the spindle motor for hard (rigid) tapping operations. For example, if the machine is going to tap a bunch 1/4-20 holes, knowing when a 3.5Kw motor goes over 100% is not particularly useful information . . . equivalent to an indicator light that says 'your tap has shattered'. :'(
As part of my tapping macro, the drive will be set at some reasonable max torque for the size tap and material being cut. Monitoring this process would involve looking at values that are some fraction of 100% and could easily be less than 10%.
-
This is the meter I used, 100uA-0-100uA.
http://www.andersmeters.com/shop.php?p=search_results&search_terms=CV18XCZ100UAS+
Here is a vid of it in action.
In the video I am spinning the chuck (250mm/10Inch Dia) to 2000rpm pause for 2 seconds then to zero pause again then to 2000 reverse and then again back to zero.
As you can see the meter shows almost 150% load whilst accelerating but settles when at speed then when stopping there is approx a 100% load in the opposite direction, then vice versa with the reverse.
http://youtu.be/lZ7asQ2PBGQ
I was at one point going to input the analogue signal to Mach for doing things such as detecting tool wear but the issue I had was the +/-10v signal. I used a rectifier so that it was always 0-10v but of course that introduced a 1.4 or so voltage drop, I then messed around with an opamp circuit to try and redress the drop but in the end I got bored and just shoved on the analogue meter ;D
Hood
-
in the end I got bored and just shoved on the analogue meter ;D
Wuss! ;D
+/-10V -> bias by 10V -> 0..20V -> 4:1 pot divider -> 0..5V ADC
-
If I had a clue what you were talking about I may agree ;D
Hood
-
Long ago I tired the spindle load to monitor feedrate. It worked OK. Simply looked at spindle rpm VS requested RPM and IF it dropped beyond a certain percentage I adjusted the SSO to allow the spindle to catch up. I brought the VFD signal in with Modbus. Also built in a deadband to keep the SSO from constantly adjusting the feedrate.
BUT the end results it did not help anything IF you did your part with programing.
Might be useful to LOAD your machine to MAX the machine capacity BUT that does not always work out well UNLESS you are using a very expensive CAM to create Constant Chiploads as most manual or low end CAM programming does not create a constant load strategy and the actual chip load is all over the place.
Just a thought, (;-)TP
-
Yes milling would be hard to do for such things, turning much simpler though as you feed per rev and one day we may even get CSS ::)
Hood
-
If I had a clue what you were talking about I may agree ;D
Hood
It's the heat you know - I spec you're still up to your oxters in snow up there right? ;D
-
I kind of see what your talking about now, it was two things that threw me, 0..20v, was thinking you had the second . in the wrong place but now see you are meaning 0-20v and the other thing was I am wanting 0-10v so your 4:1 divider giving 0-5v was also throwing me.
Still not grasping exactly how it would work though, would have to think about it a bit more as the way I am seeing it at the moment the range would be much smaller as the -10 would be 0 and 0 would be 5.
Now the weather, i wish it was snowing, I like the cold, this 26 deg C is killing me.
Hood
-
The .. is a programmer (spit!) thing for range.
The idea was just to bias (add to) your input (-10V..+10V) to make it 0V..20V (still the same range (20V) but all +ve). Then just divide it by whatever to give you your ADC input range. So let's say for example your ADC is 10 bit with an input range of 10V. You just divide by two and then feed it into your ADC then map the ADC output in software (Brain/macro whatever). So an ADC value of 0 would map to your original -10V, 512 to ~0V and 1023 to +10V.
Me - I love this weather - 7 freaking years since last summer! ;D
Ian
-
See what you are saying now :)
I will certainly be doing this when/if Brian ever gets his finger out his arse and gets Mach3 sorted or Mach4 Turn done so I can get threading with the CSMIO without the annular groove. As soon as that is possible then the ESS will be getting replaced by a CSMIO/IP-A.
Hood
-
I will certainly be doing this when/if Brian ever gets his finger out his arse
What!!! - You mean he's typing one handed? FM - that's gotta slow things down alright ;D
Ian
-
Putting a voltmeter on the VFD will tell you nothing of value. You need to be looking at current, which means putting an ammeter *in series* with one phase of the motor. The Tormach load meter is nothing but an analog ammeter. An analog ammeter contains a shunt, which is a very small, precisely known resistance. When current passes through it, it creates a small voltage drop (typically 50mV at maximum allowed current), and the meter itself is a very sensitive voltmeter, connected across the shunt, that reads full-scale with 50mV across it. Look at digikey, mouser, and other electroincs supply houses, and find one with a suitable full-scale reading. But, a good analog ammeter will not be cheap. However, a digital meter, in this application, would be completely useless.
Putting a amp meter in series, or using a clamp on type with a VFD 3 phase output to the motor is useless. The VFD voltage is not a true sine wave and the frequency varies the motor speed. This will cause the amp meter to read incorrectly. All amp digital displays on VFD's are a calculated value corrected to 60 or 50Hz. The only way is use the 0-10V analog output or modbus.
-
Putting a amp meter in series, or using a clamp on type with a VFD 3 phase output to the motor is useless. The VFD voltage is not a true sine wave and the frequency varies the motor speed. This will cause the amp meter to read incorrectly. All amp digital displays on VFD's are a calculated value corrected to 60 or 50Hz. The only way is use the 0-10V analog output or modbus.
An analog ammeter really doesn't much care what the waveform looks like, within reasonable limits, and they certainly don't care about the frequency, as it is FAR above the frequency the meter movement can react to - they'll still read a pretty good approximation of the RMS current. And most modern VFDs will output something close to a sine wave anyway - after it gets filtered by the motor impedance. Digital meters are pretty much useless with a VFD, whether you're looking at voltage or current.
Regards,
Ray L.
-
I'm a drives field service engineer and work on VFD's up to 5000 hp. AC drives today including cheap Chinese knock off use IGBT's in the power output sections. Clamp on amp meters on the motor t-leads will not give accurate readings. Drives setup in V/Hz mode as are most low cost drive used in CNC application (not vector mode) will output without a motor connected... motor impedance (xd') has very little effect on drive filtering. I could debate drive theroy with you but I think it would be beyond most of the forum readers. I've had a number of customers state their clamp on amp meters don't agree with the drive digital display...
-
I'm a drives field service engineer and work on VFD's up to 5000 hp. AC drives today including cheap Chinese knock off use IGBT's in the power output sections. Clamp on amp meters on the motor t-leads will not give accurate readings. Drives setup in V/Hz mode as are most low cost drive used in CNC application (not vector mode) will output without a motor connected... motor impedance (xd') has very little effect on drive filtering. I could debate drive theroy with you but I think it would be beyond most of the forum readers. I've had a number of customers state their clamp on amp meters don't agree with the drive digital display...
I don't think anyone here mentioned clamp-on meters but you - When I say "analog ammeter" I'm talking about a true analog panel-mount ammeter, with a shunt and D'Arsonval meter movement. Think 1930's technology. Even most clamp-on meters these days will have digital internals - Hall Effect sensors feeding into a (probably sigma-delta) A/D converter, etc.
Regards,
Ray L.
-
I will certainly be doing this when/if Brian ever gets his finger out his arse
What!!! - You mean he's typing one handed? FM - that's gotta slow things down alright ;D
Ian
;D
-
so do I or don't I use the analog output of the VFD to show motor load. what wopuld be best would be if I can use teh 0-10V outputs on all teh drivers in my cabiunet including VFD to some input card that has a program on my compuer that shows all those load meters.
-
https://www.youtube.com/watch?v=RtxUg6BtwCs