Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Old October 28th 03, 10:24 PM
Jack Erbes
 
Posts: n/a
Default Router Speed Control - How does this work?

Someone asked if this router speed control would be okay to use with a
typical non-variable speed 1/2" drill motor (5 Amps or so).:

http://www.mlcswoodworking.com/shops.../speedcon.html

I called to get a little more info and the seller says that it is for
use with "brush type motors of up to 15 Amps" and that it is a
"voltage sensitive device that maintains constant torque".

If I understand it right, this must do more than simply drop the
voltage. I wonder if this is like a VFD in that it can vary speed
without overheating the windings? Anyone want to venture a guess on
how this works?

I'm reluctant to tell someone to do something that might fry their
drill motor. If it works as they say, for $24 and free shipping, I
might get one myself.



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Old October 28th 03, 11:05 PM
James P Crombie
 
Posts: n/a
Default Router Speed Control - How does this work?

I can't vouch for their use on a drill, but I bought my dad one to use
with larger bits in his 3hp router. Seems to work well with the router.

Jack Erbes wrote:

Someone asked if this router speed control would be okay to use with a
typical non-variable speed 1/2" drill motor (5 Amps or so).:

http://www.mlcswoodworking.com/shops.../speedcon.html

I called to get a little more info and the seller says that it is for
use with "brush type motors of up to 15 Amps" and that it is a
"voltage sensitive device that maintains constant torque".

If I understand it right, this must do more than simply drop the
voltage. I wonder if this is like a VFD in that it can vary speed
without overheating the windings? Anyone want to venture a guess on
how this works?

I'm reluctant to tell someone to do something that might fry their
drill motor. If it works as they say, for $24 and free shipping, I
might get one myself.



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--
--------------------------------------------------------------------------

James P Crombie

Summerside Machinist
Prince Edward Island Amateur Astronomer
Canada 3D Designer

E-mail
Astronomy webpage
http://www.jamescrombie.com
Rhinoceros 3D webpage http://www.jamescrombie.com/rhino/
Mirror Grinder page http://www.jamescrombie.com/pics/
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Old October 28th 03, 11:38 PM
Jeff Wisnia
 
Posts: n/a
Default Router Speed Control - How does this work?

Jack Erbes wrote:

Someone asked if this router speed control would be okay to use with a
typical non-variable speed 1/2" drill motor (5 Amps or so).:

http://www.mlcswoodworking.com/shops.../speedcon.html

I called to get a little more info and the seller says that it is for
use with "brush type motors of up to 15 Amps" and that it is a
"voltage sensitive device that maintains constant torque".

If I understand it right, this must do more than simply drop the
voltage. I wonder if this is like a VFD in that it can vary speed
without overheating the windings? Anyone want to venture a guess on
how this works?

I'm reluctant to tell someone to do something that might fry their
drill motor. If it works as they say, for $24 and free shipping, I
might get one myself.

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It should work fine with a brush type motor in a drill.

IIRC those speed controls sense the "generated" back EMF during the portions of each
half wave cycle when their controlling triac is "off" and use that voltage as a
feedback signal to help keep the motor at a constant speed in the face of varying
torque loads.

IIRI, someone please correct me...

FWIW, I picked up a similar appearing speed control device from HF when it went on sale
for less than $10 and it's worked well for me the few times I've used it on my router.

Jeff


--
Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can keep smiling when things go wrong, you've thought of someone to place the
blame on."


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Old October 29th 03, 04:23 AM
rhncue
 
Posts: n/a
Default Router Speed Control - How does this work?

I also bought one of these from H/F and have found it to be totally
useless. As I slow the speed down the torque plunges. When the rpm gets down
to about 15000 just putting the bit against a board brings the bit to a
stop.
Dick

--
Building and repair of fine custom cues at affordable
prices for real poolplayers. Over 35yrs. exp.
Richard H. Neighbors 318 Linden st. Cinti. OH
ph.# (513) 242-1700
web-site: http://www.dickiecues.com



"Jeff Wisnia" wrote in message
...
Jack Erbes wrote:

Someone asked if this router speed control would be okay to use with a
typical non-variable speed 1/2" drill motor (5 Amps or so).:


http://www.mlcswoodworking.com/shops.../speedcon.html

I called to get a little more info and the seller says that it is for
use with "brush type motors of up to 15 Amps" and that it is a
"voltage sensitive device that maintains constant torque".

If I understand it right, this must do more than simply drop the
voltage. I wonder if this is like a VFD in that it can vary speed
without overheating the windings? Anyone want to venture a guess on
how this works?

I'm reluctant to tell someone to do something that might fry their
drill motor. If it works as they say, for $24 and free shipping, I
might get one myself.

-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----


It should work fine with a brush type motor in a drill.

IIRC those speed controls sense the "generated" back EMF during the

portions of each
half wave cycle when their controlling triac is "off" and use that voltage

as a
feedback signal to help keep the motor at a constant speed in the face of

varying
torque loads.

IIRI, someone please correct me...

FWIW, I picked up a similar appearing speed control device from HF when it

went on sale
for less than $10 and it's worked well for me the few times I've used it

on my router.

Jeff


--
Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can keep smiling when things go wrong, you've thought of someone

to place the
blame on."




  #5   Report Post  
Old October 29th 03, 05:16 AM
william_b_noble
 
Posts: n/a
Default Router Speed Control - How does this work?

ok, you asked. these are triac based controls that duty cycle modulate the
input AC power - basically they delay the turn on of the AC to the motor
until a desired phase angle is reached - the later the turn on (each half
cycle) the less power is delivered to the motor. It's the same as a lamp
dimmer, but with a few parts (and a more rugged triac) to accommodate the
reverse voltage from the inductance of the motor. I have a few spare
controls scrapped from drills - if you want one, I'll send you one for a
couple of $$ postpaid.


"James P Crombie" wrote in message
...
I can't vouch for their use on a drill, but I bought my dad one to use
with larger bits in his 3hp router. Seems to work well with the router.

Jack Erbes wrote:

Someone asked if this router speed control would be okay to use with a
typical non-variable speed 1/2" drill motor (5 Amps or so).:


http://www.mlcswoodworking.com/shops...l/pages/speedc
on.html

I called to get a little more info and the seller says that it is for
use with "brush type motors of up to 15 Amps" and that it is a
"voltage sensitive device that maintains constant torque".

If I understand it right, this must do more than simply drop the
voltage. I wonder if this is like a VFD in that it can vary speed
without overheating the windings? Anyone want to venture a guess on
how this works?

I'm reluctant to tell someone to do something that might fry their
drill motor. If it works as they say, for $24 and free shipping, I
might get one myself.



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----


--
--------------------------------------------------------------------------

James P Crombie

Summerside Machinist
Prince Edward Island Amateur Astronomer
Canada 3D Designer

E-mail
Astronomy webpage
http://www.jamescrombie.com
Rhinoceros 3D webpage http://www.jamescrombie.com/rhino/
Mirror Grinder page http://www.jamescrombie.com/pics/
--------------------------------------------------------------------------





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Old October 29th 03, 06:30 AM
DeepDiver
 
Posts: n/a
Default Router Speed Control - How does this work?

"william_b_noble" wrote in message
...

ok, you asked. these are triac based controls that duty cycle modulate
the input AC power - basically they delay the turn on of the AC to the
motor until a desired phase angle is reached - the later the turn on
(each half cycle) the less power is delivered to the motor.


That sounds like PWM. Is that what these controllers are?

It is my understanding that a PWM drive will offer max torque over the speed
control range because the motor always sees peak voltage (but that the
voltage is chopped so that the average current determines the speed).

I am trying to build a power table feed for a mini mill. I've got a
high-torque 24VDC gear motor, but I'm still looking for an electronic
circuit to drive it. I know some people have used a light dimmer with the
output routed through a step-down transformer; perhaps a more version would
use one of these universal motor speed controllers in place of the light
dimmer.

Anyone have suggestions for either an economical off-the-shelf solution, or
a schematic for a basic PWM circuit?

Thanks!


  #7   Report Post  
Old October 29th 03, 06:45 AM
Don Foreman
 
Posts: n/a
Default Router Speed Control - How does this work?

On Tue, 28 Oct 2003 21:16:37 -0800, "william_b_noble"
wrote:

ok, you asked. these are triac based controls that duty cycle modulate the
input AC power - basically they delay the turn on of the AC to the motor
until a desired phase angle is reached - the later the turn on (each half
cycle) the less power is delivered to the motor. It's the same as a lamp
dimmer, but with a few parts (and a more rugged triac) to accommodate the
reverse voltage from the inductance of the motor.


I think it's better than a lamp dimmer because they claim constant
speed with varying load. They may use something like the TDA1185A
chip and associated circuitry. This chip accomplishes tachless speed
control of universal motors with positive feedback.


  #8   Report Post  
Old October 29th 03, 12:19 PM
MP Toolman
 
Posts: n/a
Default Router Speed Control - How does this work?

Shunt wound or permanent magnet DC motors are inherently constant torque
devices because the magnetic field is constant at or below base speed. Any way
to get variable armature voltage will produce variable speed at constant
torque. Most AC supplied DC motor controllers are phase controlled SCR bridges
with freewheeling diodes. PWM supplies, variac (autotransformer) with diode
bridge, or power resistor will all work.

Brush type AC/DC motors (universal motors) as found in most hand held power
tools are series wound meaning the armature current also provides the field
excitation. That is why they will run (sort of) on AC -- the magnetic field
and the armature current both reverse at the same time. The speed of a series
motor can be controlled by controlling terminal voltage. That is what simple
triac controllers and light dimmers do -- but simply reducing the terminal
voltage will also reduce the available torque. Slightly more sophisticated
controllers have a feedback circuit that senses when the motor starts to slow
below the intended speed and increases the voltage to maintain the intended
speed. This feedback allows the motor to produce constant torque. Many
variable speed power drills depend upon the operator's finger to provide this
feedback -- pushing the trigger down to maintain something like constant speed
as the tool is loaded. The better controllers, and probably the more expensive
router speed control that started this string, have an electronic feedback
circuit of some kind. The cheap HF controller that did not work very well
probably does not have an electronic feedback feature.

Mill


"william_b_noble" wrote in message
...

ok, you asked. these are triac based controls that duty cycle modulate
the input AC power - basically they delay the turn on of the AC to the
motor until a desired phase angle is reached - the later the turn on
(each half cycle) the less power is delivered to the motor.


That sounds like PWM. Is that what these controllers are?

It is my understanding that a PWM drive will offer max torque over the speed
control range because the motor always sees peak voltage (but that the
voltage is chopped so that the average current determines the speed).

I am trying to build a power table feed for a mini mill. I've got a
high-torque 24VDC gear motor, but I'm still looking for an electronic
circuit to drive it. I know some people have used a light dimmer with the
output routed through a step-down transformer; perhaps a more version would
use one of these universal motor speed controllers in place of the light
dimmer.

Anyone have suggestions for either an economical off-the-shelf solution, or
a schematic for a basic PWM circuit?

Thanks!



  #9   Report Post  
Old October 29th 03, 03:21 PM
Jack Erbes
 
Posts: n/a
Default Router Speed Control - How does this work?

On Tue, 28 Oct 2003 21:16:37 -0800, "william_b_noble"
wrote:

ok, you asked. these are triac based controls that duty cycle modulate the
input AC power - basically they delay the turn on of the AC to the motor
until a desired phase angle is reached - the later the turn on (each half
cycle) the less power is delivered to the motor. It's the same as a lamp
dimmer, but with a few parts (and a more rugged triac) to accommodate the
reverse voltage from the inductance of the motor. I have a few spare
controls scrapped from drills - if you want one, I'll send you one for a
couple of $$ postpaid.


Thanks for the good explanation. So the output is intermittent 60
cycle 115V AC. That explains why they do not overheat the windings.

I can answer the question with confidence now. And thanks for the
generous offer, I like the packaging and switching concept (off, full,
variable) on the one I referenced so if I were going to use one I'd
probably just pick one of those up.



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Old October 29th 03, 03:33 PM
Jack Erbes
 
Posts: n/a
Default Router Speed Control - How does this work?

On Wed, 29 Oct 2003 04:23:27 GMT, "rhncue"
wrote:

I also bought one of these from H/F and have found it to be totally
useless. As I slow the speed down the torque plunges. When the rpm gets down
to about 15000 just putting the bit against a board brings the bit to a
stop.
Dick


I'm wondering if the HF one is as "smart" as the one I referenced. If
I understand the replies (which answered my question very well) it may
be that the HF one is cheaper but does not use the feedback from the
motor to keep the power level up and the speed constant.

When I was stationed in Korea we used to get a lot of things that
looked great and were pretty well made but just as good as the
original item. We used to call it the "Land of not quite right". Now
it appears that China has taken over that market.



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