Making Skins #74 - Brisbane Australia

[Surfcnc]

Thanks heaps Heath, nothing like direct experience to confirm something.

Regards
Ross

[Surfcnc]

After becoming aware of the Opto-isolating devices, I have tried an non opto RS485 to RS232 converter as a test to see if MattyZee's pluggin would communicate on the serial port.

No go on that one even with the pluggin set to the correct serial port number.
The dreaded 99's for those of you familiar with the no comms state of the pluggin.

The remaining option was to look around for a USB to RS485 opto-isolated converter.
This device was my eventual choice http://www.commfront.com/USB-Serial-...-Converter.htm.
This device provided the best driver support including win7 x86 x64 and linux drivers.

Not cheap by any measure at $120 AUD but it will as a minimum protect a controller worth somewhat more costly than the adapter price.
I will let everyone know how the converter performs when it is installed and tested.

Regards
Ross

[skippy]

Ross

I've been thinking about the opto couplers what you need to do RS485 to TTL chip/converter then the opto coupler then a TTL to RS485 Chip/Converter

TTL is a 0 to +5V signal

RS232 is a -12V to +12 signal

And think from Memory
RS485 is a -5V to +5V signal

As Most opto couplers work a TTL power Levels

Regards

Skippy

[Surfcnc]

Hi Skippy

You electronics nerds never fail to amaze me with your secret code
However that does not mean us mortals can't eventually figure out what it is all about, but it just takes lots of time and effort to jump into another field knowledge.

I understand your concept here but I am hoping the USB device I have posted in the link above neatly manages any or all of this inside without my intervention.
RS485 to TTL converters here http://www.commfront.com/TTL-RS232-R...-Converter.htm are around $50 AUD.
Two of these plus an intermediate circuit pretty much covers the cost of the USB device, although some China sourced parts would probably make your proposed circuit far more economical.

Lets just say I am tiring as others before me have, but the reason I have been persistent here is to gain some practical knowledge of signal noise issues.
Gerald introduced cable shielding into the base design of the Mechmate to eliminate noise issues and now everyone assumes this as a requirement for trouble free operation.
It only became a requirement after he had the problems on the shopbots.
While a crappy, cheap and noisy VFD might not seem all that smart to install in the system it does give the opportunity to look at weakness elsewhere in the system that can then be ruled out with a different design approach.

Definitely not saying I'm going to win here and when I buy a Hitachi VFD I'll let you all know

Regards
Ross

[Surfcnc]

Today on MattZee's advice I swapped out the RS485 signal cable to an unshielded Cat5E twisted pair type cable and ran my tests again.

A significant improvement this time.
I have uploaded a rather fuzzy video on Youtube to demonstrate how it is working, see http://www.youtube.com/watch?v=De1c4RW9EtY

Connections were both ends as per the attached pics.

IMG_1133.jpg

IMG_1134.jpg

To summarise - The measures in place at this point are...
1. VFD in a steel encloure box- refer to my build photos
2. torroids on 240 input and spindle output
3. EMI filter on 240 volt input
4. Cat5E twisted pair network cable with a torriod either end
5. both of the conductors from the twisted pair have been used for each signal cable

Notes
This installation is roughed in so performance may change on the final installation.
Does it work every single time faultlessly - NO.
Is it reasonably robust - Yes

Discussion
The improvement in the VFD to Mach comms with the unshielded twisted pair indicates that external EMI is probably not the primary cause for the loss of comms.
The twisting of the wires is designed to eliminate induced interference from one comms wire to another.
This is often heard as unwanted hum on sound installations when long parallel cable runs have been used.

The twist rate used for any particular cable is specific to the signal frequency, however it may not be the primary signal but noise generated by the VFD and broadcast down the wires that is causing the problems.
Therefore although the Cat5E cable improved the signal quality and noise rejection it may not be ideal as the frequency of the noise remains unknown.
I do not have an oscilloscope to test the wires so will remain in the dark unless another VFD owner has the facilities to test for the frequencies present to try to establish what is noise and what is signal.

My purchase of the opto-isolated USB adapter may or may not have an effect on the quality of the signal to the PC
In the event the noise frequency is at or near the signal frequency it may just be happily passed through along with the signal.
However if the frequency is significantly outside of the device sensitivity it may not pass through, giving protection but in a pretty round about and expensive sort of way.

The next steps are to still look at shielding the Cat5E cable.
Trying a Cat6 cable as the twist rates are different to Cat5E (long shot)
Installing the opto -isolator.
Possibly installing two separate twisted and shielded cables for each data line on the RS485 Bus (creative genius )

Regards

Ross

[Surfcnc]

Made another rest cable this afternoon from two lengths of screened spindle motor cable.
It uses only one core from each cable for the signal and both shields are joined and grounded at the USB adapter end.

Signal Cable USB Adapter End.jpg

Signal Cable VFD End.jpg

It is really close now and quite OK with respect to adjusting feed rates and spindle speed on startup but not yet completely bullet proof.
Typically what is now happening is that the spindle might remain running when the job is finished.
The only conclusion I can draw at this point is that a minor issue with grounding or signal noise still is present in the system.
After the opto-isolation adapter is put in place I will report back.

Regards
Ross

[Richards]

Tying both conductors in a CAT-5 bundle to the same terminal would give you the same result as using a single conductor.

You might try Googling "how does twisted pair wire work" and then visit the Wikipedia page at the top of the result list.

It's been years since I studied or used RS-485, but the main reason that I researched it 'back in the day', was because it had built-in common mode rejection. If the Sig+ and the Sig- signals were connected to twisted pair conductors, RS-485 had built-in noise suppression, especially if the twisted pair was inside a shielded cable.

On of the problems with opto-isolation is signal speed. Fast opto-isolators are available, but the garden variety 4N25 type opto-isolator can take a millisecond or more to stabilize between signal changes. Most RS-485 communication runs at many times that rate.

[Surfcnc]

Thanks Mike

Skippy has pointed out my error on pairing the twisted pairs, so thanks for the clarification.
Although my installation is working better all the time my understanding of what is actually the cause of the comms issue more cloudy than ever.

I made the double shield cable with torroids on both ends of both cables that was mentioned above and it works pretty well.
As each test lasts hours, I have not been able to run more than three tests on the code I know has caused issues in the past.
To further complicate matters Aus Maddog and Skippy are having no luck at all with a similar cable so no one is happy or certain here in Aus at the moment.

Regards
Ross

[Surfcnc]

Mike

I have now read the Wiki article and as you have pointed out it states the RS 485 standard uses twisted pair. Thanks drawing my attention to that.
Given that my original lead was still in practice an untwisted pair, maybe going back and using a twisted wire plus a shield might improve it - maybe

The opto-isolating device I purchased seemed to have coverage for the required data baud rate of 9600 bps that the spindle speed control pluggin uses.
The specs say it is a 300 to 115,200 bps device.(auto-sensing and self-adjusting). The cable length would obviously have an impact on the actual baud rate available.

The device is on the way but still a week or so off, I will let the forum reader know how it goes once I can run some tests.
For the moment to ensure I have a like for like comparison test, the latest cable will stay in place and the opto device will go on to that.

Regards
Ross

[Surfcnc]

I have now got all my Estop, Pause and Resume Buttons on my machine wired up.
Just a short FAQ to get some information out on the forum about this process.

Estop - wired directly to the PMDX 122 and triggered under ports and pins- Easy

Estop.JPG

Feedhold - Wired up to pin 15
Cycle Start - Wired up to pin 13
Note :
The 3 Feedhold buttons are wired in series and triggered active low.
The 3 Cycle Start buttons are wired in parallel and are triggered active high.
Cycle start is wired this way so the machine will not START on a wiring fault.

Feedhold and Cycle Start.JPG

System Hotkeys
I had the Feedhold button working very quickly but it was some time before I realised that the commonly used term "Resume" was not applicable.
The correct term "Cycle Start" and its associated OEM Trigger code of 1000 was required, not 1005 as I had entered initially.

System Hotkeys.JPG

This reference might come in handy for anyone wanting to set up their machine buttons in the future.

Regards
Ross

[Surfcnc]

For those of you following this saga, it is nice to know I finally have a result.

Using the Chinese RS485 to USB adapter like this one, results varied from "nearly there" right thorough to hopeless loss of control.
Chinese RS485 USB Adapter.jpg

Using the CommFront USB-Serial-3 RS485 to USB adapter the system settled completely.
This device is opto isolated, industrial quality and has the drivers for all commonly used operating systems
IMG_1252.jpg

Testing with only the VFD and Mach3 running, the spindle speed could be set and changed at will through the Mach3 interface.
Particularly the high RPM range right up to max revs at 24,00 RPM caused no issues.

The machine itself was then run along with the spindle and once again no issues were found.
I test ran Gcode that had repeatedly crashed the RS 485 comms previously with the Chinese adapter in place and all went perfectly this time.
The program execution was stopped and started and the spindle speed was varied from 20,000 RPM to 24,00 RPM repeatedly with no ill effects.

The cable used for the comms was a single core from each of two shielded motor cables, in deference to the standard not twisted and with some clip on round torriods on both ends of each cable (4 round torriods).
The cable shields were not grounded in any way and only two conductors were connected to both the VFD and adapter ends.

The CommFront USB-Serial-3 adapter also gives a clear indication about what is going on with the RS 485 bus as it has both send and receive indicator LEDs.
As it was working I felt it was necessary to break it to fully test what was going on.
As Mach3 and the pluggin initialize the RS 485 comms are established.
Unplugging the USB cable will kill the bus and replugging it will not restore it.
Mach3 must be restarted in order for the device to reestablish communication with the VFD.
Under all circumstances other than deliberate unplugging of the cable the bus remained solid.

Discussion

I have read that some people were getting +5 Volts on the TX relative to ground on their adapters.
On the Chinese adapter I was unable to get anything other than a few points of a single volt.
The Comm Front USB-Serial-3 gave a strong 5 Volts on the same pin relative to ground.
I am unsure if the optoisolation has contributed to the improved perfomance of the CommFront USB-Serial-3.

Although this works in a single VFD environment additional measures such as line reactors, EMI control devices and torriods or ferrite rings may be necessary on either side of the VFD in some circumstances.
I would appreciate any others who might be willing to take on the risk and additional expense of purchasing a similar adapter to confirm the solution is robust across an number of installations.

Regards
Ross

[MetalHead]

Ross,

Thanks for all this research!! It is cool to see that you worked this through to a solution.

[Surfcnc]

Despite a busy day, it was time to cut something (anything) just to refocus on the main game.

Loaded in a 6mm end mill and mowed this little guy out in about 20 seconds flat. Might go a little slower next time
Dolfin Outline.jpg

Happy to report the new adapter just worked, then worked, then worked again.

Regards
Ross

[Surfcnc]

Ries very kindly explained the risk of static electricity blowing up the Break Out Board if a zero plate was just wired directly back to it.

I have already observed the static the spindle develops when machining plastics. The spindle is covered in fine dust that is electro-statically held to the body.
For those of you cutting wood the effect is still there but the best way to generate static, as any kid will tell you, is to shuffle your feet on a synthetic carpet.
Machining synthetic plastics is exactly the same process. An unearthed dust collector is also a massive static electricity generator as most of you would already know.

I am asking if some one can draw me a circuit diagram that connects an 4N25 optoisolator AND an LED in the circuit that lights when the contact between the tool and the zero plate is made.
I envisage the circuit would include the two wires back to the Break Out Board, the two wires ot the zero plate and the earth, the LED and also any auxiliary power not provided by the Break Out Board itself.

In my typical stepwise fashion that circuit is my next priority as to not have it in place will potentially cause damage.

RS 485 to USB Adapter
What is really needed is someone else to confirm my findings.
So far I have been under whelmed with volunteers.
Before this post gets buried by others -put your hand up even if it won't be done straight away.

Regards
Ross

[riesvantwisk]

Ross,

this is how my current setup works.

On the left you have the bob, and the little squary thing is the internal pull-up resistor that makes sure that if the contact is not connected, it shows a 1.

Since the BoB has a internal pull up, you can connect the opto-coupler directly to it. Pin 5 goes to your input pin, and pin 4 goes to your GND.

On the other side of the opto-coupler I have a 5V battery, a 390R resistor, a crocodile clamp and a 20mm touch off plate.

Some considerations:
- The reason I use the 5V battery because I needed full separation between my cabinet and the open floating wires. If I would use the 12V or 5V from the cabinet and my open wires touch mains power then I would break my cabinets internals. I cannot get a BoB easy here in Ecuador so it's good insurance for me

- Initially I had put a white bright led on my little touch-off box, but I removed that because I could only fit 3 batteries in my case and you need a little more voltage to make sure the visible and optco couplers let lid up.
If you use it for auto-z, consider this:
But thinking about that later, I decided to no care about that led, I needed to see on my computers screen that the whole system is working.

See the auto-z status, it's now off but when the input is 1, it's bright green.
Think about it, if your led is on, but some other connection is broken, and you do a auto-z then the system will break your bit and tries to press it through your touch off plate, because he will not see the input go high.

This is how my auto-z works : http://www.youtube.com/watch?v=s8d1zG0YnIg


If you really need that visible led, you need to have a battery of 6 volt, then it should work but make sure the current of both the opto-coupler and the match. You also have to put the led in series, not parallel with the opto coupler.

Ries

PS: Any electro-guru's, please correct me if I am wrong!

[Surfcnc]

Thanks Ries

That is exactly what I was after.
Your complete and full explanation of all the elements of the system just made it so easy to comprehend.

To explain my confusion all the circuit diagrams had the pins 1 and 2 on the left.
I could not figure out how the signal was going to go "backwards" from the collector to the emitter in the optocoupler.
So simple now I see it simply reversed - but not so simple sitting at the kitchen table connecting wires together randomly.

Once again thanks for the warning about the risk of static and for giving me and others the solution to protect the Break Out Board.

Regards
Ross

[Surfcnc]

I have had someone volunteer to test a similar adapter to the one I am using in their system. Many thanks.
Hopefully he will have a positive report for us after the part arrives and is installed.

Regards
Ross

[Surfcnc]

Have been working towards a solution but have not finalised all the connections yet.
So far I have mounted a small LED in the Y car box as well as two 6.5 mm phono plugs to make the connections to the plate and the alligator clip.

The phono plugs slide in very easily and also hold solidly in place.
The taped up black lump in the wire bunch is the optocoupler.
Hopefully adding the LED has not confused me to the point where Reis' circuit has been rendered in operative.

Some pics for you.
IMG_1261.jpg
IMG_1263.jpg


Regards
Ross

[smreish]

Ross,
I made an extra DUMMY phone jack with a dust seal to keep in the hole when not using my touch plate to keep the dust out of the JIC button box after I found a MDF farm starting to grow in there after about a month!

Sean

[Red_boards]

I found to my surprise that I could not use a multimeter in normal mode to check a LED circuit. Then my meter did not run enough volts to get the 240v LEDs to register in diode mode. I was figuring some sort of parallel test circuit when my smart wife phoned the Chinese supplier, chatted away and got the correct connection sequence.

Looking good, Ross. Looking good.

[Surfcnc]

Hi all

I spent the day in Tony's shed with Tony and Paul looking at the USB adapters with respect to their electronics installations.
The RS485 to USB adapter is required for both the MattZee pluggin or in the boys case the full blown Modbus installation they are using with their Hitachi VFD's.
To summarise this post refers to both the Huanyang and Hitachi VFD's commonly used on this forum

Very enlightening but the results did not come particularly easily.
This adapter - worked faultlessly. http://www.commfront.com/USB-Serial-Adapters-Converters/Isolated-USB-RS232-RS485-RS422-Converter.htm

USB-Serial-3-3.jpg

This adapter - Skippy's on Test from the seller gave good initial results but failed on further testing.
http://www.jaycar.com.au/productView...5&form=KEYWORD
Jaycar RS485 to USB.jpg

The Jaycar adapter and the Commfront adapter both share the same chip and driver.
The variation in performance is therefore not centered around these components rather other areas of difference between the two devices.
The Commfront device seems to offer additional features including opto-isolation, static protection and in built 120 ohm terminating resistors.

On installation the jaycar adapter ran well allowing adjusting of the spindle speed within any speed range but strangely bluescreened after feeholding and resuming.
This was repeatedly verified on a Win XP install despite changing com address and driver versions.

To verify the adapter was at fault we then went the extra mile and swapped out the contoller PC for a fresh machine.
We then repeated the bluescreening behavior after seting up Mach and configuring the Modbus settings.
On this new PC controller machine we were able to regain stable operation with the commfront USB adapter.
Note : I have independantly verified the stable operation of the Commfront adapter under Win7.

For a while there, especially as the adapters shared chips and drivers, we though we had a good adapter on our hands.
My specially powerful button pushing and breaking things talents proved otherwise !!.

Learnt plenty including a bit about Modbus, what does work and what doesn't and most importantly Skippy and Tony now have a real clear direction forward to the super system Skippy is dreaming of.
The clouds are clearing boys and between all our grear we got this one nailed.
PS Skippy is now the designated Mechmate Forum Modbus and Brains expert

Regards
Ross

[Surfcnc]

Hi Sean and Red

Sean - good idea I will work on that one.
Lets see what I can come up with.

Red - that's why you married her.
Tell here that frequently and you will STAY married.

Regards
Ross

[AuS MaDDoG]

Hi Ross,

Good to catch up today, and thanks for your help
Yep we are certainly on track now with a good outcome from today's trials and brain storming.
I have ordered Paul and my USB Opto-Isolated Converters as per your link above this afternoon, so very much looking forward to delivery of them in the next week or so and having a strong reliable system with full control over the spindle from within Mach3.
Now get on and make those touch plates Ross!!

Cheers
Tony.

[Surfcnc]

What Tony is implying is that it is prudent to not let me in your shed as I got away with some alloy from Tony and some cabling from Skippy.
In time all these gifts will be put to good use.
Thanks

Ross

[tangocharlie123]

Congratulations on having your machine working
And all the good research that you have done on the usb to serial converters and RJ-485 as I will be going down that path shortly.

See things do fall off walls.

Cheers Peter

[Surfcnc]

Hi Pete

Got to check out the Hitachi VFD's and I was impressed with the compact size and build quality.
I also saw your electronics on your build thread is well under way, so keep up the good work.

Regards
Ross

[Surfcnc]

I changed over my Amphenol Ecomate motor connectors today from straight connectors to a right angle type.
The new ones direct the motor cables flat along the line of the machine.
The parts were sourced out of the US from http://www.alliedelec.com/.
A quick search of some of our local parts suppliers prices will soon have you heading there for their products (even when delivery is factored into the equation).

I also put some new heat shrink on the cables and then put a length of solid fencing wire inside the cable wrap.
The cable could be then be bent into shape and it retains it's shape.
Another of the many jobs remaining done.

IMG_1266.jpg
IMG_1264.jpg

Regards
Ross

[Kobus_Joubert]

Looking good, just remember to put something on that open hole on the back of the stepper...tick...another job well done.

[KenC]

I just use masking tape to cover the open holes .

[Robert M]

Ross, helping some making the search easier ( I couldn’t find it ), could you tell us those part # you have ?
Tks,