Re: [Emc-users] Simple spindle speed control for mini mill

[Chris Albertson]

There is another way to isolate an analog control.  Use an LDR.   A
light-dependent resistor.   These act like normal resister but change value
depending on how much light is shining on them.Ages ago in the 1960s
people would package them in a tube with a light bulb then you have an
optically isolated analog path.  They are non-linear so this has to be
worked around.Just like a modern "opto" but they have an analog path.
You can still buy these.

There is a very old vacuum tube-based piece of recording studio gear that
is called a CLA-2 compressor/limiter.   It will keep the output volume
constant even as the input gets louder or softer.   There are two parts to
this unit, one measures the input level and adjusts the brightness of a
tiny light bulb the other half is an adjustable gain amplifier where the
gain is controlled by the LDR resistance.   These were used in AM radio
stations, ball-park PA systems, and likely 100 other places.I use a
digital simulation of this device if I record voice-over for video.
Cranked up, it makes even me sound good.I've been wanting to build a
reproduction using real tubes for a long time but the simulation works so
well.  (Another hobby is vacuum tube electronics.)

That said, optoisolated PWM or optoisolated serial seems more of a
21st-century solution and is cheap enough.   Thanks.


On Mon, Jun 1, 2020 at 8:21 AM John Dammeyer  wrote:

> > From: Gene Heskett [mailto:ghesk...@shentel.net]
> >
> > On Monday 01 June 2020 08:25:12 Dan Henderson wrote:
> >
> > > Chris, would think you would be able to connect the 0-10v output from
> > > a BOB directly to the controller middle leg output of the
> > > potentiometer.  You wouldn�t need the hot leg, but would likely need
> > > to ground the bob to the controller.
> > >
> > And that will break the mirror and let out all the smoke this stuff runs
> > on and then none of it works.  Certainly blowing the bob, possibly the
> > computers port and various bits and pieces in the computer because the
> > hot side of the line will then be connected to the computers ground.
>
> And, although compared to the MESA board,  these are really cheap,  as
> Gene and Andy have stated this too doesn't have optical isolation.  So it
> works fine with my Bergerda AC Servo but won't with the mini-mill without
> first optically isolating the PWM input and using an isolated 15V power
> supply.
> https://www.aliexpress.com/item/33021792064.html
>
> By the time you've done that the MESA is probably a better deal.
> >
> http://store.mesanet.com/index.php?route=product/product&product_id=205&search=SPIN
>
> John
>
>
>
>
>
>
>
>
> ___
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users
>


-- 

Chris Albertson
Redondo Beach, California

___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] Simple spindle speed control for mini mill

[John Dammeyer]

> From: Gene Heskett [mailto:ghesk...@shentel.net]
> 
> On Monday 01 June 2020 08:25:12 Dan Henderson wrote:
> 
> > Chris, would think you would be able to connect the 0-10v output from
> > a BOB directly to the controller middle leg output of the
> > potentiometer.  You wouldn�t need the hot leg, but would likely need
> > to ground the bob to the controller.
> >
> And that will break the mirror and let out all the smoke this stuff runs
> on and then none of it works.  Certainly blowing the bob, possibly the
> computers port and various bits and pieces in the computer because the
> hot side of the line will then be connected to the computers ground.

And, although compared to the MESA board,  these are really cheap,  as Gene and 
Andy have stated this too doesn't have optical isolation.  So it works fine 
with my Bergerda AC Servo but won't with the mini-mill without first optically 
isolating the PWM input and using an isolated 15V power supply. 
https://www.aliexpress.com/item/33021792064.html

By the time you've done that the MESA is probably a better deal.
> http://store.mesanet.com/index.php?route=product/product&product_id=205&search=SPIN

John








___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] Simple spindle speed control for mini mill

[Gene Heskett]

On Monday 01 June 2020 08:25:12 Dan Henderson wrote:

> Chris, would think you would be able to connect the 0-10v output from
> a BOB directly to the controller middle leg output of the
> potentiometer.  You wouldn’t need the hot leg, but would likely need
> to ground the bob to the controller.
>
And that will break the mirror and let out all the smoke this stuff runs 
on and then none of it works.  Certainly blowing the bob, possibly the 
computers port and various bits and pieces in the computer because the 
hot side of the line will then be connected to the computers ground.

Gizmo's like the spinx1 and pmdx-106 exist because 99.999% of those motor 
speed controllers have the adjustment pot tied to the hot side of the 
power line. Trying to connect a ground referenced control signal WILL 
let the smoke out of a lot of parts in them and in the computer.


Nearly all of these things that do this computer control are run by a pwm 
modulated signal, which serves as a charge pump to develop the nominally 
10 volt control signal, and then uses the average value of the PWM 
signal as the control signal, but its all isolated from that portion of 
the circuitry actually connected to the hot side of the power line.

I have tried several variations of this basic idea on a card, with 
various results, most with control linearity problems that have been 
markedly improved with an isolation resistor in the 47k range between 
the cards 0 to 10 volt output, and the tie point the arm of the OEM pot 
is connected to, which if the circuit is analyzed, turns out to be the 
sum point of the feedback loop controlling the speed.  And its a current 
sum, not voltage. Or was in those I've traced.

That pmdx-106 is now a discoed product, works great when connected to the 
controller in the little hf mill.  The spinx1 is very good also.

> On Mon, Jun 1, 2020 at 12:13 AM Chris Albertson
> 
>
> wrote:
> > My cheap Harbor Freight mini mill has a variable speed spindle that
> > is controlled by hand with a knob on the front of the mill.  This
> > knob turns a potentiometer.I think all mini mills work like
> > this.
> >
> > Has anyone interfaced the potentiometer to LinuxCNC?   I don't have
> > the schematic for the spindle motor controller but I assume the
> > potentiometer imply
> > sends a control voltage to control the duty cycle of a PWM
> > generator.  The motor is a simple DC brushed motor
> >
> > It seems I could use the 0 - 10 volt output from a breakout board
> > (with posible voltage conversion) to control the speed of the
> > spindle.
> >
> > Then I place an encoder on the spindle.
> >
> > Has anyone made a simple interface that replaces the potentiometer?
> >
> > I don't want to rplace the spindle moter and use a VFD.  I think
> > this shold be very simple and low-cost.
> >
> > --
> >
> > Chris Albertson
> > Redondo Beach, California
> >
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
>
> ___
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users


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 Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] Simple spindle speed control for mini mill

[Jon Elson]

On 06/01/2020 12:11 AM, Chris Albertson wrote:

My cheap Harbor Freight mini mill has a variable speed spindle that is
controlled by hand with a knob on the front of the mill.  This knob turns a
potentiometer.I think all mini mills work like this.

Has anyone interfaced the potentiometer to LinuxCNC?   I don't have the
schematic for the spindle motor controller but I assume the potentiometer imply
sends a control voltage to control the duty cycle of a PWM generator.  The
motor is a simple DC brushed motor
Most importantly, note that this speed control is NOT 
isolated from mains voltage.  So, any interface
with it needs (presumably) optical isolation.  Several 
outfits (PMDX, CNC4PC, I think) make interfaces to these 
speed controls.


Jon


___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] Simple spindle speed control for mini mill

[andy pugh]

On Mon, 1 Jun 2020 at 06:13, Chris Albertson 
wrote:

> My cheap Harbor Freight mini mill has a variable speed spindle that is
> controlled by hand with a knob on the front of the mill.  This knob turns a
> potentiometer.I think all mini mills work like this.
>

If it is a KBIC speed controller then the manual says how to drive it with
an analogue voltage.

But be aware that the potentiometer is referenced to live on the KBIC, it
must be thoroughly isolated from any logic voltages, humans or pets.

I briefly used: https://photos.app.goo.gl/a3eXKkw4EsyGfCmT6 to control a
pair of KBIC before blowing up one of the motors and switching to VFDs and
three-phase motors.

A much simpler thing is: https://photos.app.goo.gl/wMHZPQJT72wYvSsa9 which
I have used for a VFD but would probably work with the KBIC.

Or:
http://store.mesanet.com/index.php?route=product/product&product_id=205&search=SPIN

-- 
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, 1912

___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] Simple spindle speed control for mini mill

[Dan Henderson]

Chris, would think you would be able to connect the 0-10v output from a BOB
directly to the controller middle leg output of the potentiometer.  You
wouldn’t need the hot leg, but would likely need to ground the bob to the
controller.

On Mon, Jun 1, 2020 at 12:13 AM Chris Albertson 
wrote:

> My cheap Harbor Freight mini mill has a variable speed spindle that is
> controlled by hand with a knob on the front of the mill.  This knob turns a
> potentiometer.I think all mini mills work like this.
>
> Has anyone interfaced the potentiometer to LinuxCNC?   I don't have the
> schematic for the spindle motor controller but I assume the potentiometer
> imply
> sends a control voltage to control the duty cycle of a PWM generator.  The
> motor is a simple DC brushed motor
>
> It seems I could use the 0 - 10 volt output from a breakout board (with
> posible voltage conversion) to control the speed of the spindle.
>
> Then I place an encoder on the spindle.
>
> Has anyone made a simple interface that replaces the potentiometer?
>
> I don't want to rplace the spindle moter and use a VFD.  I think this
> shold be very simple and low-cost.
>
> --
>
> Chris Albertson
> Redondo Beach, California
>
> ___
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users
>

___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] Simple spindle speed control for mini mill

[Gene Heskett]

On Monday 01 June 2020 01:11:22 Chris Albertson wrote:

> My cheap Harbor Freight mini mill has a variable speed spindle that is
> controlled by hand with a knob on the front of the mill.  This knob
> turns a potentiometer.I think all mini mills work like this.
>
> Has anyone interfaced the potentiometer to LinuxCNC?   I don't have
> the schematic for the spindle motor controller but I assume the
> potentiometer imply sends a control voltage to control the duty cycle
> of a PWM generator.  The motor is a simple DC brushed motor
>
> It seems I could use the 0 - 10 volt output from a breakout board
> (with posible voltage conversion) to control the speed of the spindle.
>
> Then I place an encoder on the spindle.
>
> Has anyone made a simple interface that replaces the potentiometer?
>
No, the only time I did it. I used a pmdx-106. Wasn't low cost.  Gave 
very stiff speed control.  Its out of service now though.  Someone 
should make me an offer.  Its complete, fwd-rev both lcnc and manual 
controls and will include a beefed up controller that can do at least a 
400 watt motor.

> I don't want to rplace the spindle moter and use a VFD.  I think this
> shold be very simple and low-cost.


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 Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

[Emc-users] Simple spindle speed control for mini mill

[Chris Albertson]

My cheap Harbor Freight mini mill has a variable speed spindle that is
controlled by hand with a knob on the front of the mill.  This knob turns a
potentiometer.I think all mini mills work like this.

Has anyone interfaced the potentiometer to LinuxCNC?   I don't have the
schematic for the spindle motor controller but I assume the potentiometer imply
sends a control voltage to control the duty cycle of a PWM generator.  The
motor is a simple DC brushed motor

It seems I could use the 0 - 10 volt output from a breakout board (with
posible voltage conversion) to control the speed of the spindle.

Then I place an encoder on the spindle.

Has anyone made a simple interface that replaces the potentiometer?

I don't want to rplace the spindle moter and use a VFD.  I think this
shold be very simple and low-cost.

-- 

Chris Albertson
Redondo Beach, California

___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users