DC potentiometer

[George Herold]

On Mar 6, 4:50 pm, Tom Biasi <tombi...@optonline.net> wrote:

On Tue, 6 Mar 2012 10:51:58 -0800 (PST), George Herold





gher...@teachspin.com> wrote:

   What a crap circuit.  The pot isn't intended for this application,
and  the low grade radio shack pots will fail in a hurry.

Jamie

I didn't think the circuit was that bad.  (But then I do some pretty
silly circuits.)

And what is that stupid zener doing there?

I thought maybe to protect the transistor?  (stop it from reverse
voltage zenering)
But I don't know motors can they send some EMF back the other way?

George H.

I would have used a darlington schematics in this case.
Two transistors would remove all the load from the potentiometer,
also allowing a wide range of potentiometer values.
Its what I used to control a batch of 12 volt ventilators
in an istrumentation package.- Hide quoted text -

- Show quoted text -

George,
This is a basic group.
The circuit you presented shows some understanding of the problem and
a way to address it.
It's not the best way to solve this but there was a time when someone
would show you how to make it better without resorting to name calling
and insults.
Check into Darlington's, power MOSFET's, and PWM and see if you can
find a better circuit.

Best Regards,
Tom- Hide quoted text -

- Show quoted text -

Thanks Tom, I'd use a Darlington too...(as Sjouke suggested.. I should
have addded that to my post)
Sorry, Sjouke

Or that National 'darlington' with thermal protection. (I can't
recall the part number)

George H.

 

[Joe Schmucker]

On Mar 4, 11:22 pm, Tom Biasi <tombi...@optonline.net> wrote:

On Sun, 4 Mar 2012 16:48:51 -0800 (PST), Joe Schmucker

wingloa...@gmail.com> wrote:
Easy question from a really dumb noob.

I have a 9volt DC motor that draws 500 ma current.  Is there a simple
potentiometer I can put on this motor to control the speed?  It is on
a wire fed welder that is either ON or OFF.  I want to control the
speed of the feed motor.

Appreciate any advice.  If you slam me for being a dorkus, I will take
it.  I'm not too thin skinned.  

Joe

You already received answers but just a comment. I don't think I have
seen a wire fed welder where the wire feed rate was not controllable.
What brand and model is your welder?
Tom

It's a Craftsman. It was the cheapest one i could get. I guess you
get what you pay for.

 

[Jamie]

Phil Hobbs wrote:

Jamie wrote:

Tom Biasi wrote:


Tom

Well, I was the one posting the original circuit and yes, it was meant
to be simple to understand.

I may have made an error on the bias current because I thought the
motor load was spec'd as 500ma., it could have been 5000ma in any
case the idea was 500ma in mind and that very simple circuit would do it
just fine..
The zener is there to suppress EMF so not to destroy the emitter in
the transistor.. The motor in that application only goes one way..

The request was for a simple circuit, that is what they got and I am
sure if 500 ma was the spec, that will work just fine..

I think some just react to soon and take it over the top.


Jamie



Sorry Jamie,
I talked to George because I was responding to his comment. I should
have addressed you.
Most of us know that you are a beginner trying to learn and will not
hesitate to ask questions.
I just don't like rude responses when they are not warranted.
I think there are many here that will help you and not rip you a new
one when you make a mistake.
Just keep doing what you are doing.

Tom

Excuse me?

A beginner?

How fucking absurd you sound...

It's obvious you sir, don't know me. what fucking place full of
clucking chickens, and you're one of them..

If you only knew what I design and work with, you'd have a totally
different view, but you don't which makes you no authority on me.

If I were the beginner as you say, then I wouldn't need a $10k Locroy
scope, a 45k Spectrum analyzer and whole lieu of other expensive toys at
my disposal and use very often. I guess that would make my employer
very incompetent, wouldn't it?

Believe what you want, I am not the beginner you say I am.. That was
a very rude and miss guided remark on your part.

I think 45 years in the field earns me the right to say so, and to
say that you have absolutely no grounds to say otherwise, except maybe,
following the advise that would rather lead you dry, because they really
don't know themselves but would rather badger others that could have an
edge on them and lose their popularity in the public eye.

Beginner my ass.

Thanks for letting me know where you stand on this, pecker head. And
hope the help from others here, works out for you. I'll be smiling as I
see the bull shitters here doing their smoke and mirror tricks.

And for the final comment..

I know the circuit is basic and is not elegant but It will work.
Have you forgotten the title on the room? I could of sat here and
designed a complete PWM driver with Mosfet switch, inductor and all that
crap, but then I guess it would get complicated for the original person
that requested it.

P.S.
I can design this shit in my sleep! I started off with a slide rule
and compiling laplace tables, and doing logs, trig, Calc on paper years
ago? how about you?

Jamie


But have a nice day.

Cheers

Phil Hobbs

Yes I will Phill, and you too

Btw, is it you that is the for most expert on diode noise?

We have a diode band gab reference that has always worked for us
perfectly, in a specific circuit that is in use as we talk until
recently. Well I should say, the diode is part of the band gap ref
circuit.

A near by addition has been done and the only foreign item
I can detect is a ~.5 WB magnetic field that wasn't there before.

I know where this field is coming from but it is clean. At less that is
what the 10ghz sweep analyzer reports minus the know noise birdies in
there, it is just a clean static mag field.

The only think I can come up with at the moment is (Eg) changing due to
temperature effects around the diode portion of the circuit which is
also a new item added to the list with this change. it does get warm now
in that area.

I am not a semiconductor engineer but heat is the only thing I can
come up with other than the near by static magnetic field that is now
present.

I am trying to determine if this is indeed some shot/johnson noise
from the diode or the jfet from end.

Also, when ever we use the Hi-z probes on the Lecroy, the problem
shifts and does not give us an accurate reading.

How does one get a real noise figure from a PN junc on the out side
world using lab equipment? Doing the temperature model does give me some
data but it is not even close to the noise we're getting in the jfet
front end. snubbing it with Caps stops the noise, however, it also
causes the circuit to not behave the way we'd like.

One of the guys in our group suggested my impedance in that area
maybe to high, which it could be, I'll need to pull off some tricks to
fix that if so

Trying to determine if this is the diode or JfET circuit..

HAGD

Jamie

 

[Phil Hobbs]

Jamie wrote:

Phil Hobbs wrote:

Jamie wrote:

Tom Biasi wrote:


Tom

Well, I was the one posting the original circuit and yes, it was meant
to be simple to understand.

I may have made an error on the bias current because I thought the
motor load was spec'd as 500ma., it could have been 5000ma in any
case the idea was 500ma in mind and that very simple circuit would do it
just fine..
The zener is there to suppress EMF so not to destroy the emitter in
the transistor.. The motor in that application only goes one way..

The request was for a simple circuit, that is what they got and I am
sure if 500 ma was the spec, that will work just fine..

I think some just react to soon and take it over the top.


Jamie



Sorry Jamie,
I talked to George because I was responding to his comment. I should
have addressed you.
Most of us know that you are a beginner trying to learn and will not
hesitate to ask questions.
I just don't like rude responses when they are not warranted.
I think there are many here that will help you and not rip you a new
one when you make a mistake.
Just keep doing what you are doing.

Tom

Excuse me?

A beginner?

How fucking absurd you sound...

It's obvious you sir, don't know me. what fucking place full of
clucking chickens, and you're one of them..

If you only knew what I design and work with, you'd have a totally
different view, but you don't which makes you no authority on me.

If I were the beginner as you say, then I wouldn't need a $10k Locroy
scope, a 45k Spectrum analyzer and whole lieu of other expensive toys at
my disposal and use very often. I guess that would make my employer
very incompetent, wouldn't it?

Believe what you want, I am not the beginner you say I am.. That was
a very rude and miss guided remark on your part.

I think 45 years in the field earns me the right to say so, and to
say that you have absolutely no grounds to say otherwise, except maybe,
following the advise that would rather lead you dry, because they really
don't know themselves but would rather badger others that could have an
edge on them and lose their popularity in the public eye.

Beginner my ass.

Thanks for letting me know where you stand on this, pecker head. And
hope the help from others here, works out for you. I'll be smiling as I
see the bull shitters here doing their smoke and mirror tricks.

And for the final comment..

I know the circuit is basic and is not elegant but It will work.
Have you forgotten the title on the room? I could of sat here and
designed a complete PWM driver with Mosfet switch, inductor and all that
crap, but then I guess it would get complicated for the original person
that requested it.

P.S.
I can design this shit in my sleep! I started off with a slide rule
and compiling laplace tables, and doing logs, trig, Calc on paper years
ago? how about you?

Jamie


But have a nice day.

Cheers

Phil Hobbs

Yes I will Phill, and you too

Btw, is it you that is the for most expert on diode noise?

We have a diode band gab reference that has always worked for us
perfectly, in a specific circuit that is in use as we talk until
recently. Well I should say, the diode is part of the band gap ref
circuit.

A near by addition has been done and the only foreign item
I can detect is a ~.5 WB magnetic field that wasn't there before.

I know where this field is coming from but it is clean. At less that is
what the 10ghz sweep analyzer reports minus the know noise birdies in
there, it is just a clean static mag field.

The only think I can come up with at the moment is (Eg) changing due to
temperature effects around the diode portion of the circuit which is
also a new item added to the list with this change. it does get warm now
in that area.

I am not a semiconductor engineer but heat is the only thing I can
come up with other than the near by static magnetic field that is now
present.

I am trying to determine if this is indeed some shot/johnson noise
from the diode or the jfet from end.

Also, when ever we use the Hi-z probes on the Lecroy, the problem
shifts and does not give us an accurate reading.

How does one get a real noise figure from a PN junc on the out side
world using lab equipment? Doing the temperature model does give me some
data but it is not even close to the noise we're getting in the jfet
front end. snubbing it with Caps stops the noise, however, it also
causes the circuit to not behave the way we'd like.

One of the guys in our group suggested my impedance in that area
maybe to high, which it could be, I'll need to pull off some tricks to
fix that if so

Trying to determine if this is the diode or JfET circuit..

HAGD

Jamie

Can you post the circuit?

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

 

[Michael A. Terrell]

George Herold wrote:

On Mar 6, 11:13 am, Sjouke Burry <s@b> wrote:
"Michael A. Terrell" <mike.terr...@earthlink.net> wrote innews:-sidncPzUPfLMcjSnZ2dnUVZ_rednZ2d@earthlink.com:







Jamie wrote:

Joe Schmucker wrote:

Easy question from a really dumb noob.

I have a 9volt DC motor that draws 500 ma current. Is there a
simple potentiometer I can put on this motor to control the speed?
It is on a wire fed welder that is either ON or OFF. I want to
control the speed of the feed motor.

Appreciate any advice. If you slam me for being a dorkus, I will
take it. I'm not too thin skinned.

Joe

Welder DC Power for Motor (+) polarity.

-o _/o-------+----------------+
/ | |
| |
| |
+ 100 +
.-. ___ |/
| |<-- -|___|- -| NPN power Transistor
10K POT | | |
'-' |
+ +---+---------+
| .--+---. |
| | | |
| | Motor| |
| | | z 12V zener
| | | A
+ '---+--' |
GND | |
+--------+
===
GND
(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

heat sink mount the transistor and pay attention because the tab is
connected to the center leg on most. That is, when using a TO-220
type package part.
These things can be gotten from radio shaft if you want to pay the
price.

What a crap circuit. The pot isn't intended for this application,
and the low grade radio shack pots will fail in a hurry.

Jamie


I didn't think the circuit was that bad. (But then I do some pretty
silly circuits.)

The 10K pot is a sick joke, or a sign of insanity.

And what is that stupid zener doing there?

Another sick joke. Diodes _are_ used to protect from back EMF, but
that?

I thought maybe to protect the transistor? (stop it from reverse
voltage zenering)
But I don't know motors can they send some EMF back the other way?

An adjutable voltage regulator, pot & resistor would be much better.
It would provide the desired control, with better speed regulation.


http://www.national.com/mpf/LM/LM317.html#Overview is an example for a
1A circuit. You can add one or more pass transistors to increase the
current, if needed. The one I built for my workbench 30+ years ago
would provide 4 to 16 volts at up to 45 amps.



--
You can't have a sense of humor, if you have no sense.

 

[Michael A. Terrell]

Jamie wrote:

Tom Biasi wrote:

Tom

Well, I was the one posting the original circuit and yes, it was meant
to be simple to understand.

I may have made an error on the bias current because I thought the
motor load was spec'd as 500ma., it could have been 5000ma in any
case the idea was 500ma in mind and that very simple circuit would do it
just fine..
The zener is there to suppress EMF so not to destroy the emitter in
the transistor.. The motor in that application only goes one way..

The request was for a simple circuit, that is what they got and I am
sure if 500 ma was the spec, that will work just fine..

I think some just react to soon and take it over the top.


Jamie



Sorry Jamie,
I talked to George because I was responding to his comment. I should
have addressed you.
Most of us know that you are a beginner trying to learn and will not
hesitate to ask questions.
I just don't like rude responses when they are not warranted.
I think there are many here that will help you and not rip you a new
one when you make a mistake.
Just keep doing what you are doing.

Tom
Excuse me?

A beginner?

How fucking absurd you sound...

It's obvious you sir, don't know me. what fucking place full of
clucking chickens, and you're one of them..

If you only knew what I design and work with, you'd have a totally
different view, but you don't which makes you no authority on me.

If I were the beginner as you say, then I wouldn't need a $10k Locroy
scope, a 45k Spectrum analyzer and whole lieu of other expensive toys at
my disposal and use very often. I guess that would make my employer
very incompetent, wouldn't it?

It's spelled 'LeCroy', you idiot. The problem is that they are toys,
because you are clueless. It's no wonder you won't use your real name:

---
Maynard A Philbrook JR KA1LPA
Willimantic, CT 06226
We are the original "Brand Rex" company
---

Believe what you want, I am not the beginner you say I am.. That was
a very rude and miss guided remark on your part.

I suppose that you majored in English, as well.

I think 45 years in the field earns me the right to say so, and to
say that you have absolutely no grounds to say otherwise, except maybe,
following the advise that would rather lead you dry, because they really
don't know themselves but would rather badger others that could have an
edge on them and lose their popularity in the public eye.

You've wasted 45 years to be so clueless?

Beginner my ass.

You look like a typical beginner, with delusions of adaquecy.

Thanks for letting me know where you stand on this, pecker head. And
hope the help from others here, works out for you. I'll be smiling as I
see the bull shitters here doing their smoke and mirror tricks.

And for the final comment..

I know the circuit is basic and is not elegant but It will work.

By what definition of 'work'?

Have you forgotten the title on the room?

This is a USENET NEWSGROUP, not a chatroom. The newsgroup is called
sci.electronics.basics NOT sci.electronics.absurd. You constantly make
a fool of yourself on sci.electronics.design and other electronics
newsgroups, then killfile those who expose your mistakes. Do you still
think that an Electret is a crystal microphone? Or claim that ECG & NTE
never shipped one good part?

I could of sat here and designed a complete PWM driver with Mosfet
Mosfet switch, inductor and all that crap, but then I guess it would
get complicated for the original person that requested it.

'I could of sat here'? If you could design it, you would have so
stop lying. Hell, you could have just pointed them to the national
Semiconductor websie & their free 'Simple Switcher' design tools, but
you aren't even that smart.

P.S.
I can design this shit in my sleep! I started off with a slide rule
and compiling laplace tables, and doing logs, trig, Calc on paper years
ago? how about you?

Then wake up and do a real design, because that is a shit design.

Sliderule, AKA: 'Slipstick' which in the wrng hands is slipshod.

One look at your website shows what an expert you are.



http://webpages.charter.net/jamie_5/I_index.htm
--
You can't have a sense of humor, if you have no sense.

 

[Tom Biasi]

On Tue, 06 Mar 2012 20:13:53 -0500, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

Tom Biasi wrote:

Tom

Well, I was the one posting the original circuit and yes, it was meant
to be simple to understand.

I may have made an error on the bias current because I thought the
motor load was spec'd as 500ma., it could have been 5000ma in any
case the idea was 500ma in mind and that very simple circuit would do it
just fine..
The zener is there to suppress EMF so not to destroy the emitter in
the transistor.. The motor in that application only goes one way..

The request was for a simple circuit, that is what they got and I am
sure if 500 ma was the spec, that will work just fine..

I think some just react to soon and take it over the top.


Jamie



Sorry Jamie,
I talked to George because I was responding to his comment. I should
have addressed you.
Most of us know that you are a beginner trying to learn and will not
hesitate to ask questions.
I just don't like rude responses when they are not warranted.
I think there are many here that will help you and not rip you a new
one when you make a mistake.
Just keep doing what you are doing.

Tom
Excuse me?

A beginner?

How fucking absurd you sound...

It's obvious you sir, don't know me. what fucking place full of
clucking chickens, and you're one of them..

If you only knew what I design and work with, you'd have a totally
different view, but you don't which makes you no authority on me.

If I were the beginner as you say, then I wouldn't need a $10k Locroy
scope, a 45k Spectrum analyzer and whole lieu of other expensive toys at
my disposal and use very often. I guess that would make my employer
very incompetent, wouldn't it?

Believe what you want, I am not the beginner you say I am.. That was
a very rude and miss guided remark on your part.

I think 45 years in the field earns me the right to say so, and to
say that you have absolutely no grounds to say otherwise, except maybe,
following the advise that would rather lead you dry, because they really
don't know themselves but would rather badger others that could have an
edge on them and lose their popularity in the public eye.

Beginner my ass.

Thanks for letting me know where you stand on this, pecker head. And
hope the help from others here, works out for you. I'll be smiling as I
see the bull shitters here doing their smoke and mirror tricks.

And for the final comment..

I know the circuit is basic and is not elegant but It will work.
Have you forgotten the title on the room? I could of sat here and
designed a complete PWM driver with Mosfet switch, inductor and all that
crap, but then I guess it would get complicated for the original person
that requested it.

P.S.
I can design this shit in my sleep! I started off with a slide rule
and compiling laplace tables, and doing logs, trig, Calc on paper years
ago? how about you?

Jamie
Well perhaps I confused you with someone else who posts under the name

of Jamie. Most of what I have seen under that name is beginner
material.
Perhaps you could have said "You must be mistaking me for someone
else." There was no need for name calling, I intended no insult.

Tom

 

[George Herold]

On Mar 7, 5:48 am, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:

George Herold wrote:

On Mar 6, 11:13 am, Sjouke Burry <s@b> wrote:
"Michael A. Terrell" <mike.terr...@earthlink.net> wrote innews:-sidncPzUPfLMcjSnZ2dnUVZ_rednZ2d@earthlink.com:

Jamie wrote:

Joe Schmucker wrote:

Easy question from a really dumb noob.

I have a 9volt DC motor that draws 500 ma current.  Is there a
simple potentiometer I can put on this motor to control the speed?
It is on a wire fed welder that is either ON or OFF.  I want to
control the speed of the feed motor.

Appreciate any advice.  If you slam me for being a dorkus, I will
take it.  I'm not too thin skinned.  

Joe

  Welder DC Power for Motor (+) polarity.

   -o _/o-------+----------------+
     /          |                |
                |                |
                |                |
                +      100       +
               .-.      ___    |/
               | |<-- -|___|- -|   NPN power Transistor
       10K POT | |             |
               '-'               |
                +                +---+---------+
                |                 ..--+---.     |
                |                 |      |     |
                |                 | Motor|     |
                |                 |      |     z 12V zener
                |                 |      |     A
                +                 '---+--'     |
               GND                    |        |
                                      +--------+
                                     ==> > > >>                                      GND
(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

heat sink mount the transistor and pay attention because the tab is
connected to the center leg on most. That is, when using a TO-220
type package part.
   These things can be gotten from radio shaft if you want to pay the
   price.

   What a crap circuit.  The pot isn't intended for this application,
and  the low grade radio shack pots will fail in a hurry.

Jamie

I didn't think the circuit was that bad.  (But then I do some pretty
silly circuits.)

   The 10K pot is a sick joke, or a sign of insanity.

Yeah, I was just looking at the circuit 'idea' and not the
execution.

And what is that stupid zener doing there?

   Another sick joke.  Diodes _are_ used to protect from back EMF, but
that?

So better protection would be a diode across the BE junction? Hmm,
that doesn't give a low impedance path for the current. (?) Or can
you have 'reverse' current flowing through the BC junction?

I thought maybe to protect the transistor?  (stop it from reverse
voltage zenering)
But I don't know motors can they send some EMF back the other way?

   An adjutable voltage regulator, pot & resistor would be much better.
It would provide the desired control, with better speed regulation.

http://www.national.com/mpf/LM/LM317.html#Overviewis an example for a
1A circuit.  You can add one or more pass transistors to increase the
current, if needed.  The one I built for my workbench 30+ years ago
would provide 4 to 16 volts at up to 45 amps.

OK, but without the added pass transistor you loose a bit of voltage
'head room' with the LM317.

I've only done ~3A type circuits... most of the time with an opamp
driving a pass transistor.

George H.

--
You can't have a sense of humor, if you have no sense.- Hide quoted text -

- Show quoted text -

 

[ehsjr]

George Herold wrote:

On Mar 7, 5:48 am, "Michael A. Terrell" <mike.terr...@earthlink.net
wrote:

George Herold wrote:


On Mar 6, 11:13 am, Sjouke Burry <s@b> wrote:

"Michael A. Terrell" <mike.terr...@earthlink.net> wrote innews:-sidncPzUPfLMcjSnZ2dnUVZ_rednZ2d@earthlink.com:

Jamie wrote:

Joe Schmucker wrote:

Easy question from a really dumb noob.

I have a 9volt DC motor that draws 500 ma current. Is there a
simple potentiometer I can put on this motor to control the speed?
It is on a wire fed welder that is either ON or OFF. I want to
control the speed of the feed motor.

Appreciate any advice. If you slam me for being a dorkus, I will
take it. I'm not too thin skinned.

Joe

Welder DC Power for Motor (+) polarity.

-o _/o-------+----------------+
/ | |
| |
| |
+ 100 +
.-. ___ |/
| |<-- -|___|- -| NPN power Transistor
10K POT | | |
'-' |
+ +---+---------+
| .--+---. |
| | | |
| | Motor| |
| | | z 12V zener
| | | A
+ '---+--' |
GND | |
+--------+
===
GND
(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

heat sink mount the transistor and pay attention because the tab is
connected to the center leg on most. That is, when using a TO-220
type package part.
These things can be gotten from radio shaft if you want to pay the
price.

What a crap circuit. The pot isn't intended for this application,
and the low grade radio shack pots will fail in a hurry.

Jamie

I didn't think the circuit was that bad. (But then I do some pretty
silly circuits.)

The 10K pot is a sick joke, or a sign of insanity.


Yeah, I was just looking at the circuit 'idea' and not the
execution.

And what is that stupid zener doing there?

Another sick joke. Diodes _are_ used to protect from back EMF, but
that?


So better protection would be a diode across the BE junction? Hmm,
that doesn't give a low impedance path for the current. (?) Or can
you have 'reverse' current flowing through the BC junction?

The diode in his circuit should be a regular diode, not a
zener. Why he chose a zener is a mystery.

Ed

I thought maybe to protect the transistor? (stop it from reverse
voltage zenering)
But I don't know motors can they send some EMF back the other way?

An adjutable voltage regulator, pot & resistor would be much better.
It would provide the desired control, with better speed regulation.

http://www.national.com/mpf/LM/LM317.html#Overviewis an example for a
1A circuit. You can add one or more pass transistors to increase the
current, if needed. The one I built for my workbench 30+ years ago
would provide 4 to 16 volts at up to 45 amps.


OK, but without the added pass transistor you loose a bit of voltage
'head room' with the LM317.

I've only done ~3A type circuits... most of the time with an opamp
driving a pass transistor.

George H.

--
You can't have a sense of humor, if you have no sense.- Hide quoted text -

- Show quoted text -

 

[John Fields]

On Sun, 4 Mar 2012 16:48:51 -0800 (PST), Joe Schmucker
<wingloader@gmail.com> wrote:

Easy question from a really dumb noob.

I have a 9volt DC motor that draws 500 ma current. Is there a simple
potentiometer I can put on this motor to control the speed? It is on
a wire fed welder that is either ON or OFF. I want to control the
speed of the feed motor.

Appreciate any advice. If you slam me for being a dorkus, I will take
it. I'm not too thin skinned.

---
A pot won't work because the motor's torque will drop off quickly as
the voltage across it drops.

You need something that produces fixed torque out of the motor, with a
variable duty cycle to control the speed, like this: (view with a
fixed-pitch font)

+9V>--+------------------------+------+-----+------+
| |8 | | |K
[4K7] +---+---+ | [MOTOR][DIODE]
| 7|_ Vcc _|4 | | |
[100K]<-+--------------O|D R|O-+ +------+
|CW | 6| | | |
[4K7] +-[1N4148>]-+---|TH 555| | |
| | 2| _|3 | D
+------[<1N4148]-+--O|TR OUT|O-|---G NCH
| | GND | | S
|+ +---+---+ | |
[1ľF] |1 [100nF] |
| | | |
GND>-------------------+-------+------+-----+

With the values shown the 555's output frequency will be about 12Hz,
and with the pot turned max clockwise, the motor will be running at
about 95% duty cycle With it turned max counter-clockwise it'll be
running at about 5%.

Choose a MOSFET which can handle the motor's stall current rating and
it ought to work pretty well.

Here's an LTspice circuit list so you can simulate it if you wan to:

Version 4
SHEET 1 936 748
WIRE -128 -576 -256 -576
WIRE 160 -576 -128 -576
WIRE 464 -576 160 -576
WIRE 736 -576 464 -576
WIRE 832 -576 736 -576
WIRE 736 -544 736 -576
WIRE -128 -528 -128 -576
WIRE 832 -528 832 -576
WIRE 160 -480 160 -576
WIRE 208 -480 160 -480
WIRE 528 -480 432 -480
WIRE 736 -432 736 -464
WIRE 832 -432 832 -464
WIRE 832 -432 736 -432
WIRE -128 -416 -128 -448
WIRE -80 -416 -128 -416
WIRE 32 -416 0 -416
WIRE 208 -416 32 -416
WIRE 496 -416 432 -416
WIRE -80 -352 -128 -352
WIRE 32 -352 32 -416
WIRE 32 -352 0 -352
WIRE 64 -352 32 -352
WIRE 160 -352 128 -352
WIRE 208 -352 160 -352
WIRE 560 -352 432 -352
WIRE 688 -352 640 -352
WIRE -128 -320 -128 -352
WIRE 464 -288 464 -576
WIRE 464 -288 432 -288
WIRE -256 -208 -256 -576
WIRE -128 -208 -128 -240
WIRE 64 -208 -128 -208
WIRE 160 -208 160 -352
WIRE 160 -208 128 -208
WIRE 160 -192 160 -208
WIRE 496 -192 496 -416
WIRE 496 -192 160 -192
WIRE 160 -176 160 -192
WIRE -256 -96 -256 -128
WIRE 160 -96 160 -112
WIRE 160 -96 -256 -96
WIRE 528 -96 528 -480
WIRE 528 -96 160 -96
WIRE 736 -96 736 -336
WIRE 736 -96 528 -96
WIRE -256 -32 -256 -96
WIRE -128 96 -256 96
WIRE 160 96 -128 96
WIRE 464 96 160 96
WIRE 736 96 464 96
WIRE 832 96 736 96
WIRE 736 128 736 96
WIRE -128 144 -128 96
WIRE 832 144 832 96
WIRE 160 192 160 96
WIRE 208 192 160 192
WIRE 528 192 432 192
WIRE 736 240 736 208
WIRE 832 240 832 208
WIRE 832 240 736 240
WIRE -128 256 -128 224
WIRE -80 256 -128 256
WIRE 32 256 0 256
WIRE 208 256 32 256
WIRE 496 256 432 256
WIRE -80 320 -128 320
WIRE 32 320 32 256
WIRE 32 320 0 320
WIRE 64 320 32 320
WIRE 160 320 128 320
WIRE 208 320 160 320
WIRE 560 320 432 320
WIRE 688 320 640 320
WIRE -128 352 -128 320
WIRE 464 384 464 96
WIRE 464 384 432 384
WIRE -256 464 -256 96
WIRE -128 464 -128 432
WIRE 64 464 -128 464
WIRE 160 464 160 320
WIRE 160 464 128 464
WIRE 160 480 160 464
WIRE 496 480 496 256
WIRE 496 480 160 480
WIRE 160 496 160 480
WIRE -256 576 -256 544
WIRE 160 576 160 560
WIRE 160 576 -256 576
WIRE 528 576 528 192
WIRE 528 576 160 576
WIRE 736 576 736 336
WIRE 736 576 528 576
WIRE -256 640 -256 576
FLAG -256 640 0
FLAG -256 -32 0
SYMBOL Misc\\NE555 320 288 M0
SYMATTR InstName U1
SYMBOL cap 176 496 M0
WINDOW 0 -33 32 Left 2
WINDOW 3 -39 58 Left 2
SYMATTR InstName C1
SYMATTR Value 1ľ
SYMBOL diode 64 336 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D1
SYMATTR Value 1N4148
SYMBOL diode 128 448 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D2
SYMATTR Value 1N4148
SYMBOL res 544 304 M90
WINDOW 0 -34 55 VBottom 2
WINDOW 3 -32 52 VTop 2
SYMATTR InstName R3
SYMATTR Value 100
SYMBOL Misc\\NE555 320 -384 M0
SYMATTR InstName U2
SYMBOL res -96 -432 M90
WINDOW 0 -34 55 VBottom 2
WINDOW 3 -32 52 VTop 2
SYMATTR InstName R6
SYMATTR Value 1K
SYMBOL res 16 -336 M270
WINDOW 0 -34 58 VTop 2
WINDOW 3 -40 61 VBottom 2
SYMATTR InstName R7
SYMATTR Value 99K
SYMBOL cap 176 -176 M0
WINDOW 0 -33 32 Left 2
WINDOW 3 -39 58 Left 2
SYMATTR InstName C2
SYMATTR Value 1ľ
SYMBOL diode 64 -336 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D3
SYMATTR Value 1N4148
SYMBOL diode 128 -224 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D4
SYMATTR Value 1N4148
SYMBOL res -112 -544 M0
SYMATTR InstName R8
SYMATTR Value 4.7K
SYMBOL res 544 -368 M90
WINDOW 0 -34 55 VBottom 2
WINDOW 3 -32 52 VTop 2
SYMATTR InstName R10
SYMATTR Value 100
SYMBOL nmos 688 -432 R0
SYMATTR InstName M2
SYMATTR Value FDS6930A
SYMBOL res 720 -560 R0
SYMATTR InstName R11
SYMATTR Value 18
SYMBOL res 720 112 R0
SYMATTR InstName R12
SYMATTR Value 18
SYMBOL diode 848 -464 R180
WINDOW 0 -43 30 Left 2
WINDOW 3 -78 -3 Left 2
SYMATTR InstName D5
SYMATTR Value 1N4148
SYMBOL diode 848 208 R180
WINDOW 0 -43 30 Left 2
WINDOW 3 -78 -3 Left 2
SYMATTR InstName D6
SYMATTR Value 1N4148
SYMBOL voltage -256 -224 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value 9
SYMBOL voltage -256 448 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value 9
SYMBOL nmos 688 240 R0
SYMATTR InstName M1
SYMATTR Value FDS6930A
SYMBOL res -96 304 M90
WINDOW 0 68 52 VBottom 2
WINDOW 3 73 53 VTop 2
SYMATTR InstName R4
SYMATTR Value 1K
SYMBOL res 16 272 M270
WINDOW 0 66 58 VTop 2
WINDOW 3 64 55 VBottom 2
SYMATTR InstName R5
SYMATTR Value 99K
SYMBOL res -112 -336 M0
SYMATTR InstName R1
SYMATTR Value 4.7K
SYMBOL res -112 128 M0
SYMATTR InstName R2
SYMATTR Value 4.7K
SYMBOL res -112 336 M0
SYMATTR InstName R9
SYMATTR Value 4.7K
TEXT 440 176 Left 2 ;1
TEXT 440 240 Left 2 ;2
TEXT 440 304 Left 2 ;3
TEXT 440 360 Left 2 ;4
TEXT 184 368 Left 2 ;5
TEXT 184 304 Left 2 ;6
TEXT 184 240 Left 2 ;7
TEXT 184 176 Left 2 ;8
TEXT -72 -64 Right 2 !.tran .5 startup uic
TEXT 440 -496 Left 2 ;1
TEXT 440 -432 Left 2 ;2
TEXT 440 -368 Left 2 ;3
TEXT 440 -312 Left 2 ;4
TEXT 184 -304 Left 2 ;5
TEXT 184 -368 Left 2 ;6
TEXT 184 -432 Left 2 ;7
TEXT 184 -496 Left 2 ;8

The top circuit is with the pot (R8-R7) max CCW, and the bottom
circuit is at max CW.

--
JF

 

[George Herold]

On Mar 7, 2:13 pm, ehsjr <eh...@nospamverizon.net> wrote:

George Herold wrote:
On Mar 7, 5:48 am, "Michael A. Terrell" <mike.terr...@earthlink.net
wrote:

George Herold wrote:

On Mar 6, 11:13 am, Sjouke Burry <s@b> wrote:

"Michael A. Terrell" <mike.terr...@earthlink.net> wrote innews:-sidncPzUPfLMcjSnZ2dnUVZ_rednZ2d@earthlink.com:

Jamie wrote:

Joe Schmucker wrote:

Easy question from a really dumb noob.

I have a 9volt DC motor that draws 500 ma current.  Is there a
simple potentiometer I can put on this motor to control the speed?
It is on a wire fed welder that is either ON or OFF.  I want to
control the speed of the feed motor.

Appreciate any advice.  If you slam me for being a dorkus, I will
take it.  I'm not too thin skinned.  

Joe

 Welder DC Power for Motor (+) polarity.

  -o _/o-------+----------------+
    /          |                |
               |                |
               |                |
               +      100       +
              .-.      ___    |/
              | |<-- -|___|- -|   NPN power Transistor
      10K POT | |             |
              '-'               |
               +                +---+---------+
               |                 .--+---.     |
               |                 |      |     |
               |                 | Motor|     |
               |                 |      |     z 12V zener
               |                 |      |     A
               +                 '---+--'     |
              GND                    |        |
                                     +--------+
                                    ==> >>>>>>                                     GND
(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

heat sink mount the transistor and pay attention because the tab is
connected to the center leg on most. That is, when using a TO-220
type package part.
  These things can be gotten from radio shaft if you want to pay the
  price.

  What a crap circuit.  The pot isn't intended for this application,
and  the low grade radio shack pots will fail in a hurry.

Jamie

I didn't think the circuit was that bad.  (But then I do some pretty
silly circuits.)

  The 10K pot is a sick joke, or a sign of insanity.

Yeah, I was just looking at the circuit 'idea' and not the
execution.

And what is that stupid zener doing there?

  Another sick joke.  Diodes _are_ used to protect from back EMF, but
that?

So better protection would be a diode across the BE junction?  Hmm,
that doesn't give a low impedance path for the current. (?)  Or can
you have 'reverse' current flowing through the BC junction?

The diode in his circuit should be a regular diode, not a
zener.  Why he chose a zener is a mystery.

Ed

Duh, Thanks Ed, I'm kinda slow at times!

George H.

I thought maybe to protect the transistor?  (stop it from reverse
voltage zenering)
But I don't know motors can they send some EMF back the other way?

  An adjutable voltage regulator, pot & resistor would be much better.
It would provide the desired control, with better speed regulation.

http://www.national.com/mpf/LM/LM317.html#Overviewisan example for a
1A circuit.  You can add one or more pass transistors to increase the
current, if needed.  The one I built for my workbench 30+ years ago
would provide 4 to 16 volts at up to 45 amps.

OK, but without the added pass transistor you loose a bit of voltage
'head room' with the LM317.

I've only done ~3A type circuits... most of the time with an opamp
driving a pass transistor.

George H.

--
You can't have a sense of humor, if you have no sense.- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

 

[Jamie]

Phil Hobbs wrote:

Jamie wrote:

Phil Hobbs wrote:


Jamie wrote:


Tom Biasi wrote:



Tom

Well, I was the one posting the original circuit and yes, it was meant
to be simple to understand.

I may have made an error on the bias current because I thought the
motor load was spec'd as 500ma., it could have been 5000ma in any
case the idea was 500ma in mind and that very simple circuit would do it
just fine..
The zener is there to suppress EMF so not to destroy the emitter in
the transistor.. The motor in that application only goes one way..

The request was for a simple circuit, that is what they got and I am
sure if 500 ma was the spec, that will work just fine..

I think some just react to soon and take it over the top.


Jamie



Sorry Jamie,
I talked to George because I was responding to his comment. I should
have addressed you.
Most of us know that you are a beginner trying to learn and will not
hesitate to ask questions.
I just don't like rude responses when they are not warranted.
I think there are many here that will help you and not rip you a new
one when you make a mistake.
Just keep doing what you are doing.

Tom

Excuse me?

A beginner?

How fucking absurd you sound...

It's obvious you sir, don't know me. what fucking place full of
clucking chickens, and you're one of them..

If you only knew what I design and work with, you'd have a totally
different view, but you don't which makes you no authority on me.

If I were the beginner as you say, then I wouldn't need a $10k Locroy
scope, a 45k Spectrum analyzer and whole lieu of other expensive toys at
my disposal and use very often. I guess that would make my employer
very incompetent, wouldn't it?

Believe what you want, I am not the beginner you say I am.. That was
a very rude and miss guided remark on your part.

I think 45 years in the field earns me the right to say so, and to
say that you have absolutely no grounds to say otherwise, except maybe,
following the advise that would rather lead you dry, because they really
don't know themselves but would rather badger others that could have an
edge on them and lose their popularity in the public eye.

Beginner my ass.

Thanks for letting me know where you stand on this, pecker head. And
hope the help from others here, works out for you. I'll be smiling as I
see the bull shitters here doing their smoke and mirror tricks.

And for the final comment..

I know the circuit is basic and is not elegant but It will work.
Have you forgotten the title on the room? I could of sat here and
designed a complete PWM driver with Mosfet switch, inductor and all that
crap, but then I guess it would get complicated for the original person
that requested it.

P.S.
I can design this shit in my sleep! I started off with a slide rule
and compiling laplace tables, and doing logs, trig, Calc on paper years
ago? how about you?

Jamie


But have a nice day.

Cheers

Phil Hobbs

Yes I will Phill, and you too

Btw, is it you that is the for most expert on diode noise?

We have a diode band gab reference that has always worked for us
perfectly, in a specific circuit that is in use as we talk until
recently. Well I should say, the diode is part of the band gap ref
circuit.

A near by addition has been done and the only foreign item
I can detect is a ~.5 WB magnetic field that wasn't there before.

I know where this field is coming from but it is clean. At less that is
what the 10ghz sweep analyzer reports minus the know noise birdies in
there, it is just a clean static mag field.

The only think I can come up with at the moment is (Eg) changing due to
temperature effects around the diode portion of the circuit which is
also a new item added to the list with this change. it does get warm now
in that area.

I am not a semiconductor engineer but heat is the only thing I can
come up with other than the near by static magnetic field that is now
present.

I am trying to determine if this is indeed some shot/johnson noise
from the diode or the jfet from end.

Also, when ever we use the Hi-z probes on the Lecroy, the problem
shifts and does not give us an accurate reading.

How does one get a real noise figure from a PN junc on the out side
world using lab equipment? Doing the temperature model does give me some
data but it is not even close to the noise we're getting in the jfet
front end. snubbing it with Caps stops the noise, however, it also
causes the circuit to not behave the way we'd like.

One of the guys in our group suggested my impedance in that area
maybe to high, which it could be, I'll need to pull off some tricks to
fix that if so

Trying to determine if this is the diode or JfET circuit..

HAGD

Jamie


Can you post the circuit?

Cheers

Phil Hobbs
We fixed it today. This was a tedious adventure. we removed the JFETS,

which is part of the current mirror and made a vertical board so we
could remount the Jfets at a different angle to be perpendicular to the
magnetic field close by. This worked out perfectly.

This circuit is using the old style T-92 case and I believe the
component leads were acting in the field. This field is static, no
modulation or variation however, we discovered we have ultrasonic
vibration in the metal mass structure and this is very hard to remove,
at lest I don't know how to remove it and found the noise we were
getting which we finally found a way to probe it, match that same
frequency.

Our mechanical engineer looked at it today and came up with
some numbers that made it look plausible.

This circuit has to be mounted in this structure because the diodes are
actually potted in machined holes. we have one on each corner and it
measures differential of temperature.

This whole circuit gets closed up in a leaded enclosure that is part
of this major structure. You can say it is integrated in the frame work.

There is ~ 2 Mev in the surroundings at times and it is critical to
monitor the corners of the window that keeps the vacuum in check. This
window is under vacuum with a 0.001 sheet of titanium composite. If the
scan cone heats up un evenly, it warps the window and thus we lose the
seal to early in life.

We used to use PTC's instead however, they die of a early like due to
the fact that it is hard to protect them from the irradiation, using
axle lead diodes, a hole is drilled and then lead lined. The diode
slides just inside of it and potted at the ends. if we didn't do this
the diodes would die much sooner!

I'll see if I can grab a scan copy of that portion of the circuit.

Jamie

 

[Phil Allison]

"John Fields"
Joe Schmucker

I have a 9volt DC motor that draws 500 ma current. Is there a simple
potentiometer I can put on this motor to control the speed? It is on
a wire fed welder that is either ON or OFF. I want to control the
speed of the feed motor.

Appreciate any advice. If you slam me for being a dorkus, I will take
it. I'm not too thin skinned.

---
A pot won't work because the motor's torque will drop off quickly as
the voltage across it drops.

** Nonsense it won't work.

You need something that produces fixed torque out of the motor,

** Only a CCS does that.

( snip ASCII schem)

With the values shown the 555's output frequency will be about 12Hz,

** LOL !!

12 Hz PWM will *PULSE* the motor with bursts of high torque.

It will also heat the windings way more than DC current or high frequency
PWM do due to the high RMS to average ratio of a pulsed wave.

The OP's motor is likely driving a gear box with a large step down ratio so
has plenty of torque for the job - all that is needed to slow it is to
reduce the voltage across the motor.



..... Phil

 

On Sun, 04 Mar 2012 17:22:05 -0800, etpm@whidbey.com wrote:

On Sun, 4 Mar 2012 16:48:51 -0800 (PST), Joe Schmucker
wingloader@gmail.com> wrote:

Easy question from a really dumb noob.

I have a 9volt DC motor that draws 500 ma current. Is there a simple
potentiometer I can put on this motor to control the speed? It is on
a wire fed welder that is either ON or OFF. I want to control the
speed of the feed motor.

Appreciate any advice. If you slam me for being a dorkus, I will take
it. I'm not too thin skinned.

Joe
If you just use a potentiometer the torque will drop fast and the
speed regulation will be poor. You can buy kits that will control the
speed with PWM which will retain the torque and fairly good speed
regulation at lower than full speed. See the links:
http://www.canakit.com/5a-motor-speed-controller-pwm.html
http://www.electronickits.com/kit/complete/motor/ck1400.htm
This one is already assembled:
http://store.qkits.com/moreinfo.cfm/MXa066
The one at the bottom of this page is only ten bucks:
http://www.quickar.com/tkit.php
Since the welding wire experiences the same friction (pretty much)
over the speeds you will be using the motor needs to be able to
produce the same torque at lower speeds. If the speed regulation of
the wire is poor then you will have all sorts of trouble welding.
Eric

http://www.amazon.com/Dimming-Controller-LED-Lights-Ribbon/dp/B003L4KKF2/ref=pd_sim_hi_4

PWM Dimming Controller For LED Lights or Ribbon, 12 Volt 8 Amp, 3301
Price: $6.71

 

[Joe Schmucker]

Hey guys,

I just want to say how much I appreciate ALL your inputs on this.

You have all invested time and effort into helping me with a way to do
what I wanted to.

Thank you all. It really amazes me that there are so many people out
there who will take the time to reply to questions like mine with such
enthusiasm and concern.

You guys rule.

Yours truly,
Joe