Super-PID new low-cost router speed controller

[ger21]

Don't these BOB's that offer Mach (PWM) to VFD analogue, provide this?
They usually offer 0-10vdc, but I believe it can be scaled in Mach just going by an Email I got some years ago from Art when I looked into making one.
Al.

I just spent over an hour reading, and don't see where or how this can be done.

[RomanLini]

Can you suggest reading for me Gerry or Al re the Mach PWM output?

I already have some excessive RC filtering (integration) on the pot input inside the super-PID, so it may accept the PWM signal directly or just require 2 resistors (for 10v to 5v conversion) and if needed, a 100uF cap (cap for extra PWM filtering).

CarveOne- great point about adding some type of option, thanks for that. At this point the SuperPID microcontroller has a spare pin that would only require tying HI or LO to select the linear/log pot option. But there is no terminal on the PCB so the wire would require soldering to the bottom of the PCB on the micro pins, which is a little clumsy.

It's very simple for me to just produce 2 firmware versions, one with the log system for manual pot use and one linear for external 0v-5v control, but I'm not sure Val would like that as the manufacturer as it adds complexity at his end, ie programming 2 versions, testing 2 versions, shipping the right version etc... Which is the reason the original design spec autoselects 50/60 Hz mains so it's never a manufacturing issue.

My limited understanding of Mach3 is that is uses "plug-ins" so can't this be coded as a plug-in? And what would be the down side if the speed range is not exactly linear, it would still be 5000 - 30000 RPM, and have a tacho display...

I forgot to mention the SuperPID comes standard with a logic-level "tacho" output as I had heard some PC software displays RPM on the PC screen, I don't know if this has any bearing.

(edit)Gerry, I juest checked out the Homann Designs DC-03, it looks like a nice product but I don't think that it would be necessary as it seems to be an isolation board and the Super-PID already has the low voltage stuff (typically) attached to the PC ground. At this point it looks like the Mach3 PWM output can just be attached directly to the Super-PID, maybe with an additional cap needed.

[H.O]

Hi,
Out of the box Mach3 offers On/Off, PWM and step and direction control of the spindle.

On/Off is simply a signal you can tie to relay, turning the spindle on and off.

PWM is just that, a low(ish) frequency PWM signal is generated on the output pin of your choise. The frequency can be specified but the higher you go the lower resolution (available number of discrete speeds) are available. If you run Mach3 at 25kHz and set the PWM frequency to 25Hz you'll have 1000 discrete "steps" or speeds and the PWM signal can be integrated by a simple RC filter to get an analog voltage. This will likely not be very linear over the whole range but that might be able to be corrected with the Calibrate Spindle feature in Mach3 (never tried it personally).

Step and direction. This outputs step-pulses just as if the spindle was another axis. To get an analog signal the step pulses is run thru a F/V converter chip such as the LM2907 which outputs a voltage proportionally to the frequency of the step-pulses. This is the type of circuit available on the CNC4PC C11 board for example. (It offers better lineratiy and better resolution than the PWM option)

Then of course you have all sorts of more "exotic" ways of controlling the spindle speed, like MODBUS and things like that.

Finally you can attach a one pulse per revolution signal to an input and have Mach3 display the true speed. The pulse must be at least 1/kernel frequency long in order for Mach3 to see properly.

/Henrik.

[Al_The_Man]

I just spent over an hour reading, and don't see where or how this can be done.

Gerry - Roman, I will see if I can dredge up the old emails, they ,may have been deleted, I will post what I find.
Al.

[ger21]

Can you suggest reading for me Gerry or Al re the Mach PWM output?

http://www.machsupport.com/docs/Mach...all_Config.pdf

Section 5, towards the end I think.

And what would be the down side if the speed range is not exactly linear, it would still be 5000 - 30000 RPM, and have a tacho display...

You program the rpm using the S word in G-code. S20000 for 20K rpm. Downside is you wouldn't get what you expect. But it might be close enough.

If the PWM works straight from Mach3 into the SuperPID, that would be great.

[RomanLini]

Hi,
Out of the box Mach3 offers On/Off, PWM and step and direction control of the spindle.

On/Off is simply a signal you can tie to relay, turning the spindle on and off.

That is directly compatible with the "RUN" input of the Super-PID.

PWM is just that, a low(ish) frequency PWM signal is generated on the output pin of your choise. The frequency can be specified but the higher you go the lower resolution (available number of discrete speeds) are available. If you run Mach3 at 25kHz and set the PWM frequency to 25Hz you'll have 1000 discrete "steps" or speeds and the PWM signal can be integrated by a simple RC filter to get an analog voltage.

Good information, thanks! That should connect ok direct to the Super-PID instead of the pot. I would suggest a change of the existing 2.2uF in the SuperPID to (say) 220uF.

This will likely not be very linear over the whole range but that might be able to be corrected with the Calibrate Spindle feature in Mach3 (never tried it personally).

I will look into the calibrate feature.

Step and direction. This outputs step-pulses just as if the spindle was another axis. To get an analog signal the step pulses is run thru a F/V converter chip such as the LM2907 which outputs a voltage proportionally to the frequency of the step-pulses. This is the type of circuit available on the CNC4PC C11 board for example. (It offers better lineratiy and better resolution than the PWM option)

More good info thanks. It may be possible for the SuperPID to directly interpret the pulse frequency but it's microcontroller is already worked pretty hard running the PID, phase control and LCD all in real time!

Finally you can attach a one pulse per revolution signal to an input and have Mach3 display the true speed. The pulse must be at least 1/kernel frequency long in order for Mach3 to see properly.

This shouldn't be a problem, the Super-PID "TACHO" output is logic level and 1 pulse per spindle rotation, somewhere near 50:50 duty so at 30000 RPM will be (worse case) 500uS pulse width which is well within your 1/25kHz needs. So it looks like you get tacho display on Mach3 with the standard SuperPID.


Al- thanks, any info you can provide will be appreciated, particularly on how the "racalibrate spindle" feature works, and if the PWM RPM must be 0-30000 RPM or if it can be offset to 5000-30000 RPM.

Ger21- Thanks I've downloaded the PDF you suggested and will check it out.

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Here are a couple of pictures of my Super-PID display unit, it was just cut from black and clear acrylic with a tongue and slot design. The switch on the right is "RUN" and the two switches on the left are for "STABLE MODE" and "OPEN LOOP MODE" which are two inbuilt features you can connect if you choose.

The lead shows how I just bought a $5.95 mains extension lead and cut it in the middle to provide the mains in/out plugs and some mains rated cable. There's no way I could have bought the 2 mains plugs and 3 metres of good cable for $5.95!

Videos of operation have been taken, I just need to work out how to use that Youtube thing and I will post links then.

[ger21]

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Here are a couple of pictures of my Super-PID display unit, it was just cut from black and clear acrylic with a tongue and slot design. The switch on the right is "RUN" and the two switches on the left are for "STABLE MODE" and "OPEN LOOP MODE" which are two inbuilt features you can connect if you choose.

I'm guessing the run is On/Off? We can probably control that with mach3 as well?

Is "Open Loop" basically bypassing the Super-PID?

What does "Stable Mode" do?

Hope we get a manual with this.

Right now I plug my router in above the machine. I'm going to have run a shielded cable through my E-chain.

I'll also need to run the sensor through there. You said it's pre-wired, but I'll probably need 4-5 meters. I'm guessing this should be shielded as well?

[RomanLini]

Hi Gerry, the manual is basically written but waiting on some trimmings like a few diagrams and photos etc. It will be a .PDF very shortly.

To answer your questions;
1. The "RUN" is indeed for turning the router on/off, it is a logic level input and meant to be connected to your PC, Mach3 or EMC etc. I used a switch for the display unit for convenience.
2. "OPEN-LOOP MODE" bypasses the spindle sensor and just turns the power up/down to the router like an old fashioned speed control. It still has the tacho RPM display and still shows the power bargraph display, but there is no PID closed-loop system controlling things, just a simple knob. This is useful for testing, or if you need to use the speed control with no spindle sensor (or if the sensor fails you can switch straight to open loop and maybe finish the job). It won't give the low RPM power of the PID system but it might be useful for some cases.
3. "STABLE MODE" changes the PID settings to more heavily damped settings. The normal settings are very stable and specifically tuned for routers for the best power and stability, but if for some reason there is evidence of oscillation you can use the "stable" setting. This mode, being heavily damped, gives slightly slower response to loads and less perfect speed regulation but it is still speed regulated and offers similar high power. Generally it should not be needed but I thought it was a pro type feature even if only for testing or special cases.

The unit I sent to you has 3 metres of shielded cable (2 core + shield) attached to the sensor. Sorry if I had known you needed 5 I could have supplied it that way! I have tested the sensor wire next to the router power and stepper wires and not seen any interference so far as it has numerous layers of hardware and software filtering for the sensor signal but like any device I can't speak for every case! You should not need to shield the router power wires as the phase angle system used doesn't generate the amount of nasty noise that some PWM spindle controllers do. Maybe I can check your build log photos and suggest a wiring scheme based on that?

It's official! I'm a TERRIBLE cameraman...

Video of Super-PID booting up, then the "Spindle View" mode showing LCD bargraph that changes as the spindle is turned. This feature is active anytime the router is stopped, so you can always see the spindle sensor output.
[nomedia="http://www.youtube.com/watch?v=L8IsjkTxAs0"]YouTube - Super-PID CNC spindle view mode[/nomedia]

Video of "Pot View" mode. If you turn the pot fast when the router is stopped the bargraph shows the pot position, to see the pot is functioning perfectly (in case of remote pot mounting or to see an external speed vontrol voltage etc).
[nomedia="http://www.youtube.com/watch?v=NYvStyUbeII"]YouTube - Super-PID CNC pot view mode[/nomedia]

Video of open-loop test. The spindle is set to about 10% power, which settles out about 5800 RPM. Then when a chunk of wood is mashed into the 5mm endmill the spindle speed drops down to stall. This video demonstrates the very poor router power at low RPMs, ie before the PID system is turned on.
[nomedia="http://www.youtube.com/watch?v=qJdOAj0hei0"]YouTube - Super-PID CNC open-loop spindle test[/nomedia]

The video shows the Super-PID set to its lowest speed of 5000 RPM, you can see the tacho 4998-5002 or so, keeping speed within a fraction of a percent. Even at this low speed when the wood is again mashed into the tool (a nasty test!) the speed barely droops (maybe 2%) then recovers back to 5000 and chews the wood right up now it has some decent power. Then the speeds 5000-10000-15000-20000-30000 etc are shown and you can see the power bargraph rise to show the increase in power sent to the router. Then a 8000 RPM wood mash test.
[nomedia="http://www.youtube.com/watch?v=85L050QcsYI"]YouTube - Super-PID CNC 5000 to 30000 RPM PID[/nomedia]

Fun video of cutting some oval pockets in acrylic with a 5mm 4-flute endmill at 8000 RPM, giving no melt and sharp clear edges.
[nomedia="http://www.youtube.com/watch?v=NIHa6_MpN7A"]YouTube - Super-PID CNC cutting acrylic 8000 RPM[/nomedia]

Second video of that job, this time drilling the acrylic at 5000 RPM with a 1/8" standard drill bit. No coolant or pecking is needed and due to the reliable RPM, the swarf is beautiful constant long swirls. The holes are again sharp and clean with no evidence of melt. (I'm very happy with the SuperPID for drilling!)
[nomedia="http://www.youtube.com/watch?v=oBJ4Ebo-_HU"]YouTube - Super-PID drilling acrylic at 5000 RPM[/nomedia]

Here's a photo of the oval pocket and drill test after I cleaned it you can see the neat walls and almost glass-like cut surfaces;
(and sorry for the long post and for the wobby camera work!)

[ger21]

The unit I sent to you has 3 metres of shielded cable (2 core + shield) attached to the sensor. Sorry if I had known you needed 5 I could have supplied it that way! I have tested the sensor wire next to the router power and stepper wires and not seen any interference so far as it has numerous layers of hardware and software filtering for the sensor signal but like any device I can't speak for every case! You should not need to shield the router power wires as the phase angle system used doesn't generate the amount of nasty noise that some PWM spindle controllers do. Maybe I can check your build log photos and suggest a wiring scheme based on that?

3 meters might work. Since I plan on moving the Super PID to a future machine, I think I can mount it closer.

My bigger concern with the spindle power is running it with the stepper wires.

Looking at the last pic here, 3 meters may not be long enough, as it's almost 2 meters up the gantry side and across.

http://www.cnczone.com/forums/671212-post176.html

Then when a chunk of wood is mashed into the 5mm endmill the spindle speed drops down to stall

That looks safe.

Second video of that job, this time drilling the acrylic at 5000 RPM with a 1/8" standard drill bit...........

I didn't think that running at 5K will allow me to use drill bits much more safely now. I usually use a 1/8" router bit, but am limited to 1/2" depth. This will let me drill all the way through my 3/4" parts. Awesome.

[Al_The_Man]

Roman, Did you try the difference of using a bridge after the AC controller and feeding the motor with DC?
I notice that the Universal motor Treadmill controllers that have used this method with the Onsemi IC with feedback will control down to zero rpm?
I have one currently on a band saw.
Al.

[ger21]

Al, you have to remember that all the motors this will be used with are dependent on the spindle mounted cooling fan to keep them cool. He's already stated that cooling might be an issue at 5000 rpm.

Although I guess there are plenty of other applications that this might benefit.

[CarveOne]

Impressive Romanlini.

Heating of the router motor can be monitored with a thermal probe, and the corresponding current draw can be monitored with an ac current probe. There would be some sort of correlation between 5k rpm and every 5k rpm increment upward to 30k rpm that may not be linear. Each level would need to be run long enough for the router motor temperature to stabilize. It would be a useful chart to have for the more popular router models used on the DIY machines.

CarveOne

[ger21]

I believe he said that motor heating (and current draw) will vary depending on the load. With a light load, it may not even get hot at 5K rpm.

[CarveOne]

I believe he said that motor heating (and current draw) will vary depending on the load. With a light load, it may not even get hot at 5K rpm.

That's true, but it would still be a good idea to have some measurements rather than something less subjective like finger tests for heat on the router case while cutting something. If 5k is the only point of concern, then maybe a no-load, medium load, and heavy load test may be enough to see how much change there is to be expected from a particular model router.

CarveOne

[Al_The_Man]

That's true, but it would still be a good idea to have some measurements rather than something less subjective like finger tests for heat on the router case while cutting something.
CarveOne

The majority of commercial CNC spindles have have either a thermal switch or a thermistor attached to the stator, probably would not be difficult to incorporate that if turns out to be needed.
Al.

[RomanLini]

Gerry- I don't think you will get problems between the router power leads and your stepper driver leads, BUT if you want to use shielded cable then by all means. The spindle sensor needs a 2-core cable plus shield, any good quality stereo microphone cable will work as they are well shielded and rated for high flex cycles.

Al- My original protoype unit (see post#1 above) used bridge rectifier (ie full wave DC) and IGBT with numerous PWM and phase angle systems tested. There is no benefit and for the final design I settled on the phase angle system for price and proven reliability and it actually has much less audible and RF noise than PWM systems.

Re the treadmill motor, these are always designed for very high torques at low RPM. Total opposites of router motors that have light weight armatures and are optimised for best powerband at 20000+ RPM. There's really not a lot of options to get better performance out of a router, believe me i've been tuning it for weeks... This is about as good as it gets.

CarveOne- Thanks! Heating really is not that big an issue. As you can see in the video cutting oval pockets with 5mm endmill, the power to the router goes from 10% to maybe 15%, this is a tiny amount of router heat and WELL within the cooling capacity of the router fan at 5000 RPM. The air pumped out of the router under this type of use is barely above room temperature. In any case where you are running the SuperPID at lower speeds than you currently run doing similar cutting work there will be LESS heat that you are currently getting including less bearing heat. I'll ask Val about changing that warning on the SuperPID.com page as I think it is giving people the wrong impression. Please don't stress too much about heating until you test it out for yourself doing some normal sane type cutting loads.

That is a good point about concerns at 5000 RPM, this is the most difficult RPM for the reason that the router itself was never designed to work well at 5000 RPM. What you will find at 5000 RPM if you try to take a ridiculously heavy cut is that rather than overheating the router will probably experience oscillation as the Super-PID tries to squeeze power from the rotuer that it is just not capable of producing at 5000 RPM.

Again I don't want to give people the impression that this is a problem, the Super-PID is capable of getting amazing low speed performance out of the router but there are finite limits to how well a 25k router can ever be made to work at 5k! If you need to drill steel with a 3/8" drill bit at 5000 RPM this is not the way to do it. Buy a big cast-iron drill press.

Al- Re the thermal sensor it's slightly different to commercial spindles. They only have multiphase windings in the stator and permanent magnet rotor so it is easier to do that. With a router, the stator field windings don't get very hot, the majority of the heat will be in the armature windings. An air temp sensor would be easiest and probably the smartest.

I am open to suggestions re a heat sensor or something but really people need to try these out, see that their routers can be run at lower RPMs with *less* heat and wear than they are currently getting for the majority of tasks and then go from there. At this point I just don't see it being needed as my router is running cooler, quieter, more precise etc. It would always be possible to cook a router through inappropriate use whether it has a PID or not.

[CarveOne]

I'm in no way suggesting that the Super PID be changed to include a temperature monitoring display function. Only that someone test it and have a chart or curve available to show what is happening at the lowest usable speed. That speed may be different for different routers. (?)

I would expect that under normal loads, at low rpm the current drawn will be less, and there is less heat to be to be dispersed by the fan anyway.

CarveOne

[RomanLini]

It's all good, please keep the comments coming I very much respect your opinion and it gives useful insight as to how people who are experienced in CNC routing perceive the unknown product re potential benefits/problems etc.

The idea of a temperature sensor and temperature shown on the display is actually a good idea. Maybe for a future version of the Super-PID it could be added without adding too much cost to the product and it would add value and perceived value. It's an idea that I would not have had myself, but now with your (and Al's) input it is now under consideration, so thank you both.

Re the Mach3 control, thanks Gerry I read through the Mach3 PDF and at this point it looks like the Mach3 PWM output could drive the Super-PID speed control, but not at linear RPM so there would be some user input needed to tell the PC to send out X PWM to then make the PID run at Y RPM. I'll keep looking into this.

In the meantime if anyone has cutting tests etc they would like to see I will have the video camera for a few more days.

[Al_The_Man]

Al- Re the thermal sensor it's slightly different to commercial spindles. They only have multiphase windings in the stator and permanent magnet rotor so it is easier to do that. With a router, the stator field windings don't get very hot, the majority of the heat will be in the armature windings. An air temp sensor would be easiest and probably the smartest.

I am thinking about DC spindles with wound field, the temp sensor is buried in the stator and being as these are shunt wound motors the heat IS generated in the rotor, but paradoxically they monitor the stator, as it is hard to monitor a rotor.
But with the router motors having the same current in both field and armature, I would have thought they would heat about equal?
Al.

[RomanLini]

Sorry Al I thought you were talking about VFD spindles! Series wound universal motors like routers generally have less than 20% of the applied voltage dropped by each series winding and the field windings have a larger cooling area. Generally with failed power tools it's the armature or commutator that goes first rather than either field winding.

If a motor is being operated well outside its safe operating area the whole thing will get hot. With forced air cooling the exhaust air will give a pretty good idea of the overall motor heat I think.