Motor control help

M

Mark Monson

Guest
I'm an inventor with little electronics knowledge. What I want to do is
reduce the speed of a woodworking router from 30,000 RPM to about 7,000 RPM.
I need a compact circuit that can be mass produced for OEM. The router
draws about 10 amps full load at 120V AC. The brush type motor will
always operate at the same reduced speed.

I've used a commercially made external speed control but it's noisy and the
speed kind of hunts around. Any help is appreciated.

MM
 
Mark Monson wrote:
I'm an inventor with little electronics knowledge. What I want to do is
reduce the speed of a woodworking router from 30,000 RPM to about 7,000 RPM.
I need a compact circuit that can be mass produced for OEM. The router
draws about 10 amps full load at 120V AC. The brush type motor will
always operate at the same reduced speed.

I've used a commercially made external speed control but it's noisy and the
speed kind of hunts around. Any help is appreciated.

Router motors are generally universal wound types (universal, because
Click to expand...
they can operate from AC or DC). This kind of motor has very poor
speed regulation but can handle a wide range of load torques by
varying its speed. No simple voltage or current regulating circuit
will provide very good speed control (especially under varying torque
load) for this kind of motor without some independent speed feedback
mechanism.

--
John Popelish
 
"John Popelish" <jpopelish@rica.net> wrote in message
news:4012E2AD.6E5A17CC@rica.net...
Mark Monson wrote:

I'm an inventor with little electronics knowledge. What I want to do
is
reduce the speed of a woodworking router from 30,000 RPM to about 7,000
RPM.
I need a compact circuit that can be mass produced for OEM. The router
draws about 10 amps full load at 120V AC. The brush type motor will
always operate at the same reduced speed.

I've used a commercially made external speed control but it's noisy and
the
speed kind of hunts around. Any help is appreciated.

Router motors are generally universal wound types (universal, because
they can operate from AC or DC). This kind of motor has very poor
speed regulation but can handle a wide range of load torques by
varying its speed. No simple voltage or current regulating circuit
will provide very good speed control (especially under varying torque
load) for this kind of motor without some independent speed feedback
mechanism.
Click to expand...
OK. My question is still what specific circuit I need to knock the speed
down to about 7,000 RPM. This is application doesn't require precision
speed. It's a power tool. I don't need feedback loop accuracy.

MM
--
John Popelish
Click to expand...
 
Mark Monson wrote:

OK. My question is still what specific circuit I need to knock the speed
down to about 7,000 RPM. This is application doesn't require precision
speed. It's a power tool. I don't need feedback loop accuracy.

You don't take a hint very well. I don't think you are going to find
Click to expand...
a circuit that satisfies you, but you might try something like the
second one on:

http://www.st.com/stonline/products/support/motor/uni.htm

I don't have component values for it, though.

--
John Popelish
 
"John Popelish" <jpopelish@rica.net> wrote in message
news:4015C821.1E034889@rica.net...
Mark Monson wrote:

OK. My question is still what specific circuit I need to knock the
speed
down to about 7,000 RPM. This is application doesn't require precision
speed. It's a power tool. I don't need feedback loop accuracy.

You don't take a hint very well.
Click to expand...
You don't answer questions very well. Maybe because you don't know the
answers. In any case, universal motors are commonly controlled by simple
trigger type speed switches as found on VSR drills, and high/low switches as
found on Milwaukee's Sawsall. All I need is a similar circuit that has a
fixed rather than variable speed reduction built into it. Maybe somebody
else out there is better qualified to help. Thanks for your time.

MM

I don't think you are going to find
a circuit that satisfies you, but you might try something like the
second one on:

http://www.st.com/stonline/products/support/motor/uni.htm

I don't have component values for it, though.

--
John Popelish
Click to expand...
 
Mark Monson wrote:

"John Popelish" <jpopelish@rica.net> wrote in message
news:4015C821.1E034889@rica.net...

Mark Monson wrote:

OK. My question is still what specific circuit I need to knock the
speed
down to about 7,000 RPM. This is application doesn't require precision
speed. It's a power tool. I don't need feedback loop accuracy.

You don't take a hint very well.

You don't answer questions very well.
Click to expand...
Actually his answer(s) was supurb.

Maybe because you don't know the answers.
Click to expand...
You failed to understand that there is no fixed
answer to your question.

In any case, universal motors are commonly controlled by simple
trigger type speed switches as found on VSR drills, and high/low switches as
found on Milwaukee's Sawsall.
Click to expand...
Trigger speed switched rely on a feedback loop, the user. The sawzall
2 speed switch does not give fixed speeds.

All I need is a similar circuit that has a
fixed rather than variable speed reduction built into it. Maybe somebody
else out there is better qualified to help. Thanks for your time.
Click to expand...
You are clarly in over your depth.
 
Mark Monson wrote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:4015C821.1E034889@rica.net...

You don't take a hint very well.

You don't answer questions very well.
Click to expand...
I explained the reason that a fixed speed control is very difficult
for universal motors. And that it is possible to produce such a
thing, but that it requires a speed feedback mechanism. I admitted my
limitations in not being able to do what you need.

Maybe because you don't know the
answers. In any case, universal motors are commonly controlled by simple
trigger type speed switches as found on VSR drills, and high/low switches as
found on Milwaukee's Sawsall. All I need is a similar circuit that has a
fixed rather than variable speed reduction built into it. Maybe somebody
else out there is better qualified to help. Thanks for your time.
Click to expand...
If they are and respond, I will learn something. Good luck.

--
John Popelish
 
"Mark Monson" <m_monson@ztech.com> wrote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:4015C821.1E034889@rica.net...
Mark Monson wrote:

OK. My question is still what specific circuit I need to knock the
speed
down to about 7,000 RPM. This is application doesn't require precision
speed. It's a power tool. I don't need feedback loop accuracy.

You don't take a hint very well.

You don't answer questions very well. Maybe because you don't know the
answers. In any case, universal motors are commonly controlled by simple
trigger type speed switches as found on VSR drills, and high/low switches as
found on Milwaukee's Sawsall. All I need is a similar circuit that has a
fixed rather than variable speed reduction built into it. Maybe somebody
else out there is better qualified to help. Thanks for your time.
Click to expand...
The killer here was your requirement of "about 7000rpm". That implies
a (roughly) constant speed is important to you. Speed control is easy,
but relatively constant speed under varying load is much harder.

You seem to think that "fixed rather than variable speed reduction" is
a trivial distinction. You are very, very wrong. It is an important
distinction in terms of electronics design - the distinction being the
requirement for feedback.

A simple speed controller controls only the power to the motor. Power
and bit speed (rpm) have no direct relationship. To include rpm in the
equation you need feedback (of the rpm).

Your question was phrased in terms of rpm. You got a good answer. If
you're not happy with it I suggest you learn why a speed controller
which controls the power to a motor is different to one which controls
its rpm, then re-phrase the question. I think that's what John was
hinting at. Actually, his first answer wasn't a hint: It was a lesson,
which you failed to take on board.


Tim
--
The .sig is dead.
 
You don't take a hint very well.
John Popelish

You don't answer questions very well.
Mark Monson
Click to expand...
Actually, around these parts
Popelish is known as patient, even-tempered, and informative.

If John tells you that you're a bozo
(though he never would never say so in so many words),
chances are you're a bozo.
 
"JeffM" <jeffm_@email.com> wrote in message
news:f8b945bc.0401291625.61da687@posting.google.com...
You don't take a hint very well.
John Popelish

You don't answer questions very well.
Mark Monson

Actually, around these parts
Popelish is known as patient, even-tempered, and informative.

If John tells you that you're a bozo
(though he never would never say so in so many words),
chances are you're a bozo.
Click to expand...
Well said!
 
I have a motor speed control circuit that works well. I found it in an
electronics mag many years ago, built several of them and they work very
well.One was installed in the foot peddle of a sewing machine and I use one
on a woodworking router with excellent results.It will run any AC motor with
brushes and maintain a constant speed regardless of loading.
Most motor speed controllers work much like lamp dimmers in that they
reduce the RMS voltage applied to the motor, with no feedback the actual RPM
of the motor will vary dependant with the load applied. (A variable speed
drill has feedback, the operator will squeeze the trigger more as the drill
is loaded and slows down.)
This particular circuit applies power to the motor during the positive half
cycle of the AC sine wave, during the negative half of the cycle it measures
the back EMF of the motor. As the motor is loaded and slows down, the back
EMF will drop, a comparator senses the change and increases the voltage
applied to maintain the selected speed.
I'm sure this circuit is exactly what you're looking for Mark.
Anyone wants the mag article, I will scan it and send it by email.

Kevin Wile
Halifax NS
Canada



"Mark Monson" <m_monson@ztech.com> wrote in message
news:A7jRb.1109$qR3.940@bignews3.bellsouth.net...
"John Popelish" <jpopelish@rica.net> wrote in message
news:4012E2AD.6E5A17CC@rica.net...
Mark Monson wrote:

I'm an inventor with little electronics knowledge. What I want to do
is
reduce the speed of a woodworking router from 30,000 RPM to about
7,000
RPM.
I need a compact circuit that can be mass produced for OEM. The
router
draws about 10 amps full load at 120V AC. The brush type motor will
always operate at the same reduced speed.

I've used a commercially made external speed control but it's noisy
and
the
speed kind of hunts around. Any help is appreciated.

Router motors are generally universal wound types (universal, because
they can operate from AC or DC). This kind of motor has very poor
speed regulation but can handle a wide range of load torques by
varying its speed. No simple voltage or current regulating circuit
will provide very good speed control (especially under varying torque
load) for this kind of motor without some independent speed feedback
mechanism.

OK. My question is still what specific circuit I need to knock the speed
down to about 7,000 RPM. This is application doesn't require precision
speed. It's a power tool. I don't need feedback loop accuracy.

MM
--
John Popelish
Click to expand...
 
"krikkit" <kevin3@canoemail.com> wrote in message
news:xNpSb.12389$Ja2.71034@nnrp1.uunet.ca...
I have a motor speed control circuit that works well. I found it in an
electronics mag many years ago, built several of them and they work very
well.One was installed in the foot peddle of a sewing machine and I use
one
on a woodworking router with excellent results.It will run any AC motor
with
brushes and maintain a constant speed regardless of loading.
Most motor speed controllers work much like lamp dimmers in that they
reduce the RMS voltage applied to the motor, with no feedback the actual
RPM
of the motor will vary dependant with the load applied. (A variable speed
drill has feedback, the operator will squeeze the trigger more as the
drill
is loaded and slows down.)
This particular circuit applies power to the motor during the positive
half
cycle of the AC sine wave, during the negative half of the cycle it
measures
the back EMF of the motor. As the motor is loaded and slows down, the back
EMF will drop, a comparator senses the change and increases the voltage
applied to maintain the selected speed.
I'm sure this circuit is exactly what you're looking for Mark.
Anyone wants the mag article, I will scan it and send it by email.
Click to expand...
OK. You're saying that reducing the voltage will reduce the speed. I know
this works with DC motors on DC power, but I didn't know this would work
with Universal motors on AC power. So I could add a resister in series or
electronically clip the AC waveform to reduce the voltage.

This particular application may do fine with a simple voltage reduction
because the working load on the motor is relatively constant and far below
the power reserve even at half of the full speed rating.

Thanks for your help.

MM


Kevin Wile
Halifax NS
Canada



"Mark Monson" <m_monson@ztech.com> wrote in message
news:A7jRb.1109$qR3.940@bignews3.bellsouth.net...

"John Popelish" <jpopelish@rica.net> wrote in message
news:4012E2AD.6E5A17CC@rica.net...
Mark Monson wrote:

I'm an inventor with little electronics knowledge. What I want to
do
is
reduce the speed of a woodworking router from 30,000 RPM to about
7,000
RPM.
I need a compact circuit that can be mass produced for OEM. The
router
draws about 10 amps full load at 120V AC. The brush type motor
will
always operate at the same reduced speed.

I've used a commercially made external speed control but it's noisy
and
the
speed kind of hunts around. Any help is appreciated.

Router motors are generally universal wound types (universal, because
they can operate from AC or DC). This kind of motor has very poor
speed regulation but can handle a wide range of load torques by
varying its speed. No simple voltage or current regulating circuit
will provide very good speed control (especially under varying torque
load) for this kind of motor without some independent speed feedback
mechanism.

OK. My question is still what specific circuit I need to knock the
speed
down to about 7,000 RPM. This is application doesn't require precision
speed. It's a power tool. I don't need feedback loop accuracy.

MM
--
John Popelish
Click to expand...
 
OK. You're saying that reducing the voltage will reduce the speed.
I know this works with DC motors on DC power,
but I didn't know this would work with Universal motors on AC power.
So I could add a resister in series
or electronically clip the AC waveform to reduce the voltage.
Mark Monson
Click to expand...
No. That's not what he's saying at all.
Changing the voltage level (amplitude) is NOT the way to do this.
He's talking about a "phase controller" as Popelish already has.
The technique is akin to "pulse-width modulation" on DC motors.
The group has already told you this will allow you to CHANGE the
speed,
is not going to achieve REGULATION.


To the group:
Has anyone got experience with using
a Rotational Speed Governor on an electric motor?
http://images.google.com/images?hl=en&lr=lang_en&ie=UTF-8&oe=UTF-8&safe=off&q=governor+trainweb+diesel&btnG=Google+Search
 
JeffM wrote:
OK. You're saying that reducing the voltage will reduce the speed.
I know this works with DC motors on DC power,
but I didn't know this would work with Universal motors on AC power.
So I could add a resister in series
or electronically clip the AC waveform to reduce the voltage.
Mark Monson

No. That's not what he's saying at all.
Changing the voltage level (amplitude) is NOT the way to do this.
He's talking about a "phase controller" as Popelish already has.
The technique is akin to "pulse-width modulation" on DC motors.
The group has already told you this will allow you to CHANGE the
speed,
is not going to achieve REGULATION.

To the group:
Has anyone got experience with using
a Rotational Speed Governor on an electric motor?
http://images.google.com/images?hl=en&lr=lang_en&ie=UTF-8&oe=UTF-8&safe=off&q=governor+trainweb+diesel&btnG=Google+Search
Click to expand...
Sure. My wife's Kitchen Aid mixer has one in it. I added some spark
suppression components to it to make the contacts last longer.

--
John Popelish
 
What I am saying is that this circuit that I have built, tested and use
regularly does achieve regulation of the motor's speed. It applies power to
the motor during the positive half of the AC sine wave, measures the back
EMF of the motor during the negative half of the cycle. It will increase the
power being applied if the speed has fallen below the desired RPM's because
of increased loading. When the load decreases, it senses the increase in
back EMF voltage and compensates by lowering the voltage being applied . It
acts as a govenor, and does achieve regulation over a wide range of loads.
The motor's speed can be slowed to almost zero RPM and it will still develop
the same torque as when running full speed.
Simply adding a resistor or clipping the AC voltage will slow the motor
down but will not regulate the speed.
I've tried to find this circuit on the web but am unable to. It was
published in Electronics Today's Project Book #3 1986.
I don't have a webpage to post it to, but perhaps that would be the easiest
way as seeing it would make it much easier to understand.

Kevin Wile
Halifax NS
Canada


"JeffM" <jeffm_@email.com> wrote in message
news:f8b945bc.0401301132.fd371e5@posting.google.com...
OK. You're saying that reducing the voltage will reduce the speed.
I know this works with DC motors on DC power,
but I didn't know this would work with Universal motors on AC power.
So I could add a resister in series
or electronically clip the AC waveform to reduce the voltage.
Mark Monson

No. That's not what he's saying at all.
Changing the voltage level (amplitude) is NOT the way to do this.
He's talking about a "phase controller" as Popelish already has.
The technique is akin to "pulse-width modulation" on DC motors.
The group has already told you this will allow you to CHANGE the
speed,
is not going to achieve REGULATION.


To the group:
Has anyone got experience with using
a Rotational Speed Governor on an electric motor?

http://images.google.com/images?hl=en&lr=lang_en&ie=UTF-8&oe=UTF-8&safe=off&q=governor+trainweb+diesel&btnG=Google+Search
Click to expand...
 
Kevin

I would like to see this circuit. Can you send to it to
Jackanapes57@yahoo.com

Thank you

MM
"krikkit" <kevin3@canoemail.com> wrote in message
news:diDSb.13068$Ja2.74722@nnrp1.uunet.ca...
What I am saying is that this circuit that I have built, tested and use
regularly does achieve regulation of the motor's speed. It applies power
to
the motor during the positive half of the AC sine wave, measures the back
EMF of the motor during the negative half of the cycle. It will increase
the
power being applied if the speed has fallen below the desired RPM's
because
of increased loading. When the load decreases, it senses the increase in
back EMF voltage and compensates by lowering the voltage being applied .
It
acts as a govenor, and does achieve regulation over a wide range of loads.
The motor's speed can be slowed to almost zero RPM and it will still
develop
the same torque as when running full speed.
Simply adding a resistor or clipping the AC voltage will slow the motor
down but will not regulate the speed.
I've tried to find this circuit on the web but am unable to. It was
published in Electronics Today's Project Book #3 1986.
I don't have a webpage to post it to, but perhaps that would be the
easiest
way as seeing it would make it much easier to understand.

Kevin Wile
Halifax NS
Canada


"JeffM" <jeffm_@email.com> wrote in message
news:f8b945bc.0401301132.fd371e5@posting.google.com...
OK. You're saying that reducing the voltage will reduce the speed.
I know this works with DC motors on DC power,
but I didn't know this would work with Universal motors on AC power.
So I could add a resister in series
or electronically clip the AC waveform to reduce the voltage.
Mark Monson

No. That's not what he's saying at all.
Changing the voltage level (amplitude) is NOT the way to do this.
He's talking about a "phase controller" as Popelish already has.
The technique is akin to "pulse-width modulation" on DC motors.
The group has already told you this will allow you to CHANGE the
speed,
is not going to achieve REGULATION.


To the group:
Has anyone got experience with using
a Rotational Speed Governor on an electric motor?


http://images.google.com/images?hl=en&lr=lang_en&ie=UTF-8&oe=UTF-8&safe=off&q=governor+trainweb+diesel&btnG=Google+Search
Click to expand...
 
No luck on posting it to schematics... much too large a file.(1.4M) If
anyone wants it send an email and I'll send it as I did to Mark. I've seen
these units available at my local woodworking tool store, there's one at
this website as well, and very inexpensive I might add..
http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/speedcon.html


Kevin



"JeffM" <jeffm_@email.com> wrote in message
news:f8b945bc.0401302229.1749c907@posting.google.com...
I don't have a webpage to post it to
Kevin Wile (krikkit)

Post it to alt.binaries.schematics.electronics
and put a pointer to it here.
Click to expand...
 
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