Re: [Emc-users] Protection from back EMF?

[Gene Heskett]

On Thursday 14 June 2018 19:40:49 Chris Albertson wrote:

> This is a general motion controller question
>
> A couple days ago I blew up a pair of mosfets  What I think happened
> was I had a motor going forward then switched to reverse.   Basically
> slammed over.   The motor likely developed it's full stall current of
> 21 amps.  This blew the fuse I had on the power supply.  Then I'm
> guessing the motor finds itself inside a powerful magnetic field and
> has open circuit leads and puts some large voltage across the mosfet
> H_bridge letting some smoke out.
>
> I think that is the physics.  basically a motor and some attached
> rotational mass trying to act as a generator powering a high impedance
> circuit.   Not 100% sure I understand this well enough to calculate
> voltages.
>
> Question:  This must be a common problem.   Is it common to use some
> kind of diode voltage clamp to limit the volts across the controller?
> I've also heard of placing a reversed diode in parallel with the power
> supply fuse to basically sort the back EMF.
>
> What are people doing with DC brushed motors that work with currents
> up to a couple tens of amps?
>
I'm doing that twice, once on TLM, my 7x lathe, and once on the g0704, 
both with 1 hp at the label motors, and both with psu's bigger than the 
motors nameplate voltage and capable of 20+ amp surges, 15 till the cows 
come home.

I trip the safety shutdown latch on one of Jons pwm-servo amplifiers 
occasionally on a hard turnoff, requiring I climb the short stepstool an 
poke a plastic tool thru a hole over the reset button on Jons amp. It 
was often enough that I got into the habit of writing my gcode to slow 
the motor to 20 revs for about half second before issuing the m5 to stop 
it. However, it is  not a problem with rigid tapping as the motor is 
never out of control at high rpms unless you issue an m5 while its 
running wide open. That is where you'll trip out if you are going to 
trip out. Jons pwm-servo's also have a current limiter that is 
non-disabling, and if you listen carefully you can hear a short chirp 
from the motor when the m3-m4-m3 reversal is taking place, but I pretty 
much minimized that with a limit3 in front of the PID.command in order 
to slow the ramping of the signal to something the amplifier can handle. 
ISTR thats a setp of 400 for both the voltage and the current.
  
> What is the maximum back EMF current?  I'm guessing that a motor can
> only generate current up to it's stall current.

No, it can generate both a higher voltage and a higher current, higher 
voltage into an open circuit, and a higher current into a short circuit. 
I have seen the psu, running at 126 volts under normal load, peak above 
160 at turn around time when using Jon's amps because they absorb the 
energy when the amp is slowing the motor by dumping it back into the 
psu. Thats also above the surge rating of that huge bank of caps used 
for a filter, but its also not for long enough to heat the caps since 
the accel loading in the other direction pulls it back down to normal in 
maybe 200 milliseconds maximum.

Basically, if you are going to do spindle motor control, you have 2 
choices. A vfd with its input profiled to be brutal, but not 
destructively so, or a dc controller that does a full 4 quadrant 
control. There are others I'm sure but in the 1 or 2 horse field, Jon's 
pwm-servo is king of the crop. Properly programmed, its a hocky puck, 
you can't make it hurt itself. For instance, at 2900 revs in high gear, 
I can reach up and change the head to low gear. The secret? Two switches 
and a notch in the edge of the knob. The pid gets normal drive if either 
switch is closed, meaning the back gearing is fully engaged. But if I 
grab the knob and start to turn it, within 4 or 5 degrees of rotation 
the notch is no longer allowing the switch to be closed. That steers a 
mux4 whose inputs are for the no switch closed condition are setp'd to 
about about 20 rpm, so in a few milliseconds, much faster than I can 
turn the knob, the motor is down to creep speed, and stays there, 
facilitating the gear engagement and doesn't restore full speed until 
the knob is firmly seated in the other gear, allowing the other switch 
to close. These same signals also switch the tach range so the tach 
remains extremely accurate. As does all the signals needed for rigid 
tapping.

I obviously don't mind hacking around in hal files. :)
>
> Why did the motor go from full forward to full reverse?  In this case
> it was dutifully following a hand controller but it could result from
> other dumb things like an error in programming.
>
> I can think of all kinds of solutions but I figure some have been
> tested by time and are well known,

The limit3 module is tailor made for gentling the sequencing this stuff, 
give it a shot.

-- 
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed 

Re: [Emc-users] Protection from back EMF?

[John Dammeyer]

Hi Chris, although I haven't had a chance to test it in 'anger' so to speak
I have a voltage clamp circuit across the power supply.  Mine uses a small
PIC micro-controller and it's also used to bleed the 105VDC power supply.

Henrik Olsson published a circuit back in 2008.  I searched google and came
up with this link which may help.
https://www.cnczone.com/forums/uhu-servo-controllers/67118-regenerative-powe
r-dump-circuit.html

The Power FET generally has a diode in the opposite direction so negative
back emf is automatically clamped.  The circuits sense when the voltage goes
too high and turn on the FET to bleed down the voltage.

Mariss  from Gecko also posted some circuits that sense current back into
the power supply and also serve as a bleed.

John Dammeyer


> -Original Message-
> From: Chris Albertson [mailto:albertson.ch...@gmail.com]
> Sent: June-14-18 4:41 PM
> To: Enhanced Machine Controller (EMC)
> Subject: [Emc-users] Protection from back EMF?
> 
> This is a general motion controller question
> 
> A couple days ago I blew up a pair of mosfets  What I think happened
> was I had a motor going forward then switched to reverse.   Basically
> slammed over.   The motor likely developed it's full stall current of
> 21 amps.  This blew the fuse I had on the power supply.  Then I'm
> guessing the motor finds itself inside a powerful magnetic field and
> has open circuit leads and puts some large voltage across the mosfet
> H_bridge letting some smoke out.
> 
> I think that is the physics.  basically a motor and some attached
> rotational mass trying to act as a generator powering a high impedance
> circuit.   Not 100% sure I understand this well enough to calculate
> voltages.
> 
> Question:  This must be a common problem.   Is it common to use some
> kind of diode voltage clamp to limit the volts across the controller?
> I've also heard of placing a reversed diode in parallel with the power
> supply fuse to basically sort the back EMF.
> 
> What are people doing with DC brushed motors that work with currents
> up to a couple tens of amps?
> 
> What is the maximum back EMF current?  I'm guessing that a motor can
> only generate current up to it's stall current.
> 
> Why did the motor go from full forward to full reverse?  In this case
> it was dutifully following a hand controller but it could result from
> other dumb things like an error in programming
> 
> I can think of all kinds of solutions but I figure some have been
> tested by time and are well known,
> --
> 
> Chris Albertson
> Redondo Beach, California
> 
>

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Re: [Emc-users] Protection from back EMF?

[andy pugh]

On 15 June 2018 at 00:40, Chris Albertson  wrote:

> What are people doing with DC brushed motors that work with currents
> up to a couple tens of amps?

On my RobotWars robot (that had DC motors running hundreds of amps) I
fitted off-the-shelf bridge rectifier modules across the motors to
dump excess voltage back into the batteries (the battery voltage made
a good reference limit).

Only really an option with DC motors and battery power, I suspect.

This was actually mainly to protect the relays.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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[Emc-users] Protection from back EMF?

[Chris Albertson]

This is a general motion controller question

A couple days ago I blew up a pair of mosfets  What I think happened
was I had a motor going forward then switched to reverse.   Basically
slammed over.   The motor likely developed it's full stall current of
21 amps.  This blew the fuse I had on the power supply.  Then I'm
guessing the motor finds itself inside a powerful magnetic field and
has open circuit leads and puts some large voltage across the mosfet
H_bridge letting some smoke out.

I think that is the physics.  basically a motor and some attached
rotational mass trying to act as a generator powering a high impedance
circuit.   Not 100% sure I understand this well enough to calculate
voltages.

Question:  This must be a common problem.   Is it common to use some
kind of diode voltage clamp to limit the volts across the controller?
I've also heard of placing a reversed diode in parallel with the power
supply fuse to basically sort the back EMF.

What are people doing with DC brushed motors that work with currents
up to a couple tens of amps?

What is the maximum back EMF current?  I'm guessing that a motor can
only generate current up to it's stall current.

Why did the motor go from full forward to full reverse?  In this case
it was dutifully following a hand controller but it could result from
other dumb things like an error in programming

I can think of all kinds of solutions but I figure some have been
tested by time and are well known,
-- 

Chris Albertson
Redondo Beach, California

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[Emc-users] Sorry

[jeremy youngs]

I don't know how I trampled your thread so badly Andy .
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Re: [Emc-users] Interesting gear hobs

[andy pugh]

On 14 June 2018 at 19:51, Henk du preez  wrote:
> I think those can only be used to cut a specific size gearset with specific
> ratio.

This article:
http://gearsolutions.com/features/high-performance-gear-cuts-a-path-to-stronger-bevel-gears/

Seems to suggest that the wheel and pinion are cut with the same
cutter, so I think that they can hob any bevel at the 3.5mod tooth
pitch.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Interesting gear hobs

[Henk du preez]

I think those can only be used to cut a specific size gearset with specific
ratio.

Henk

On Thu, 14 Jun 2018, 20:40  wrote:

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> Today's Topics:
>
>1. Re: Interesting gear hobs (John Dammeyer)
>2. Re: Interesting gear hobs (andy pugh)
>3. Wester servo design (jeremy youngs)
>4. Re: Wester servo design (jeremy youngs)
>5. Fwd: Wester servo design (jeremy youngs)
>
>
> --
>
> Message: 1
> Date: Thu, 14 Jun 2018 10:12:49 -0700
> From: "John Dammeyer" 
> To: "'Enhanced Machine Controller \(EMC\)'"
> 
> Subject: Re: [Emc-users] Interesting gear hobs
> Message-ID: <1ad601d40402$eccadaf0$c66090d0$@autoartisans.com>
> Content-Type: text/plain;   charset="UTF-8"
>
> Be interesting to see a Youtube video of those in action.
> John
>
>
> > -Original Message-
> > From: andy pugh [mailto:bodge...@gmail.com]
> > Sent: June-14-18 3:03 AM
> > To: Enhanced Machine Controller (EMC)
> > Subject: [Emc-users] Interesting gear hobs
> >
> > https://www.ebay.co.uk/itm/Two-palloid-gear-cutters-KLINGELNBERG-
> > hobs-3-5-MOD-for-spiral-bevel-gears/302648042420
> >
> > For hobbing spiral bevels.
> >
> > --
> > atp
> > "A motorcycle is a bicycle with a pandemonium attachment and is
> > designed for the especial use of mechanical geniuses, daredevils and
> > lunatics."
> > ? George Fitch, Atlanta Constitution Newspaper, 1916
> >
> >
> --
> > Check out the vibrant tech community on one of the world's most
> > engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
>
>
>
>
> --
>
> Message: 2
> Date: Thu, 14 Jun 2018 18:26:48 +0100
> From: andy pugh 
> To: "Enhanced Machine Controller (EMC)"
> 
> Subject: Re: [Emc-users] Interesting gear hobs
> Message-ID:
>  tu+c4yfqbkv3+cao...@mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> On 14 June 2018 at 18:12, John Dammeyer  wrote:
> > Be interesting to see a Youtube video of those in action.
>
> I had a look (search "palloid" ) but both videos are terrible.
>
> --
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is
> designed for the especial use of mechanical geniuses, daredevils and
> lunatics."
> ? George Fitch, Atlanta Constitution Newspaper, 1916
>
>
>
> --
>
> Message: 3
> Date: Thu, 14 Jun 2018 13:15:43 -0500
> From: jeremy youngs 
> To: "Enhanced Machine Controller (EMC)"
> 
> Subject: [Emc-users] Wester servo design
> Message-ID:
> <
> ca+mq1er7ei65nd2ek5bpfp5fdef_ytasjbzf-k8ga7ko9ur...@mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> Good day fellas.
> I received these Western servo design power supply and brush less
> amplifiers. I have hounded the manufacturer to no avail for user manual.
> There is a short 2 page spec sheet for each device available at wsdi.com
> I need to know how to identify these connectors, so I can Interface with
> them. Also user manual would be great . My Google fu is failing me and I'm
> curious if anyone here may have manuals they may be willing to scan for me.
> I got this six hp kollmorgen motor and I'm chomping at the bit to see it
> spin. Any help greatly appreciated.
>
>
> --
>
> Message: 4
> Date: Thu, 14 Jun 2018 13:39:22 -0500
> From: jeremy youngs 
> To: "Enhanced Machine Controller (EMC)"
> 
> Subject: Re: [Emc-users] Wester servo design
> Message-ID:
> <
> ca+mq1esij2qvz-p881l330kqrdovmcfqrb+kmko2ejst90h...@mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
>   IMG_20180614_130755.jpg
> <
> https://drive.google.com/file/d/1oqBy-2wB3Dh9RAa1qk8lwf5HGpE-Da0o/view?usp=drivesdk
> >
>
>   IMG_20180614_130806.jpg
> <
> https://drive.google.com/file/d/1GbJp6HSsJUdwPsuHHz0-4P_liPgHWCgl/view?usp=drivesdk
> >
>
>   IMG_20180614_130819.jpg
> <
> https://drive.google.com/file/d/1UT-kicCNBAW25_L0MaGGLgyICqJZYCA-/view?usp=drivesdk
> >
>
>   wsd1.jpg
> <
> https://drive.google.com/file/d/1j6LKdzeGGJz6mK-UYNoOcWFqu45r2-99/view?usp=drivesdk
> >
> Sorry these are the drives and connectors in question
>
> On Thu, Jun 14, 2018, 1:15 PM jeremy youngs  wrote:
>
> > Good day fellas.
> > I 

Re: [Emc-users] Wester servo design

[jeremy youngs]

  IMG_20180614_130755.jpg


  IMG_20180614_130806.jpg


  IMG_20180614_130819.jpg


  wsd1.jpg

Sorry these are the drives and connectors in question

On Thu, Jun 14, 2018, 1:15 PM jeremy youngs  wrote:

> Good day fellas.
> I received these Western servo design power supply and brush less
> amplifiers. I have hounded the manufacturer to no avail for user manual.
> There is a short 2 page spec sheet for each device available at wsdi.com
> I need to know how to identify these connectors, so I can Interface with
> them. Also user manual would be great . My Google fu is failing me and I'm
> curious if anyone here may have manuals they may be willing to scan for me.
> I got this six hp kollmorgen motor and I'm chomping at the bit to see it
> spin. Any help greatly appreciated.
>
>
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[Emc-users] Fwd: Wester servo design

[jeremy youngs]

-- Forwarded message -
From: jeremy youngs 
Date: Thu, Jun 14, 2018, 1:15 PM
Subject: Wester servo design
To: Enhanced Machine Controller (EMC) 


Good day fellas.
I received these Western servo design power supply and brush less
amplifiers. I have hounded the manufacturer to no avail for user manual.
There is a short 2 page spec sheet for each device available at wsdi.com
I need to know how to identify these connectors, so I can Interface with
them. Also user manual would be great . My Google fu is failing me and I'm
curious if anyone here may have manuals they may be willing to scan for me.
I got this six hp kollmorgen motor and I'm chomping at the bit to see it
spin. Any help greatly appreciated.
--
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[Emc-users] Wester servo design

[jeremy youngs]

Good day fellas.
I received these Western servo design power supply and brush less
amplifiers. I have hounded the manufacturer to no avail for user manual.
There is a short 2 page spec sheet for each device available at wsdi.com
I need to know how to identify these connectors, so I can Interface with
them. Also user manual would be great . My Google fu is failing me and I'm
curious if anyone here may have manuals they may be willing to scan for me.
I got this six hp kollmorgen motor and I'm chomping at the bit to see it
spin. Any help greatly appreciated.
--
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Re: [Emc-users] Interesting gear hobs

[andy pugh]

On 14 June 2018 at 18:12, John Dammeyer  wrote:
> Be interesting to see a Youtube video of those in action.

I had a look (search "palloid" ) but both videos are terrible.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Interesting gear hobs

[John Dammeyer]

Be interesting to see a Youtube video of those in action.
John


> -Original Message-
> From: andy pugh [mailto:bodge...@gmail.com]
> Sent: June-14-18 3:03 AM
> To: Enhanced Machine Controller (EMC)
> Subject: [Emc-users] Interesting gear hobs
> 
> https://www.ebay.co.uk/itm/Two-palloid-gear-cutters-KLINGELNBERG-
> hobs-3-5-MOD-for-spiral-bevel-gears/302648042420
> 
> For hobbing spiral bevels.
> 
> --
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is
> designed for the especial use of mechanical geniuses, daredevils and
> lunatics."
> � George Fitch, Atlanta Constitution Newspaper, 1916
> 
> --
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> ___
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users


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[Emc-users] Interesting gear hobs

[andy pugh]

https://www.ebay.co.uk/itm/Two-palloid-gear-cutters-KLINGELNBERG-hobs-3-5-MOD-for-spiral-bevel-gears/302648042420

For hobbing spiral bevels.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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