How do I hook up my potentiometer?

[ehsjr]

Michael A. Terrell wrote:

John Fields wrote:

On Mon, 18 Feb 2008 20:24:12 GMT, ehsjr <ehsjr@bellatlantic.net
wrote:


kayvee wrote:

I have a 500k ohm POT and I will be using it to vary the voltage of a
circuit I am making. It is basically a motor which I want to be able
to change the voltage drop across it. I will be connecting it in
series with the motor. This POT I have has 3 lead coming off of it. I
am under the impression that if I connect the middle lead and one of
the outer leads it will vary the current of the circuit, and if I
connect all 3 lead in a curtain fashion it will vary the voltage.

Now my question is how do I connect the 3 leads?

I have tried reading explanations, I would appreciate a straight
forward good old fashioned diagram.

[POT}
| | |
? ? ?

*---[DC]----?---------[MOTOR]---*
| |
| |
*-------------------------------*

Connecting a pot directly to a motor is not usually
advisable. As a general rule, assume that if you do
it, you will burn out the pot. If the motor draws
less current than the pot can handle, that's ok, but
you need to know that up front.

If you use a pot to drive a transistor, you can
control a lot more current:

V+ ---+----[Motor]----+
| |
P /c
O<---[220R]---| NPN Power xsistor
T \e
| |
Gnd ---+---------------+


The NPN transistor needs to be able to handle the
power and current that the motor needs.

---

V+ ---+---------------+
| |
P /c
O<------------| NPN Power xsistor
T \e
| |
Gnd --+---[Motor]-----+

Better, yes?




Unless you turn the wiper all the way to the top terminal and destroy
the transistor. A resistor to limits the base current to a safe level
should be added between that terminal and V+. (For once I got to make
the correction before John caught it) ;-)

John has ended my plan for world domination
(see my reply to him) with his better plan:

R_Motor*(1 + Hfe)



Ed

 

[ehsjr]

John Fields wrote:

On Mon, 18 Feb 2008 20:24:12 GMT, ehsjr <ehsjr@bellatlantic.net
wrote:


kayvee wrote:

I have a 500k ohm POT and I will be using it to vary the voltage of a
circuit I am making. It is basically a motor which I want to be able
to change the voltage drop across it. I will be connecting it in
series with the motor. This POT I have has 3 lead coming off of it. I
am under the impression that if I connect the middle lead and one of
the outer leads it will vary the current of the circuit, and if I
connect all 3 lead in a curtain fashion it will vary the voltage.

Now my question is how do I connect the 3 leads?

I have tried reading explanations, I would appreciate a straight
forward good old fashioned diagram.

[POT}
| | |
? ? ?

*---[DC]----?---------[MOTOR]---*
| |
| |
*-------------------------------*

Connecting a pot directly to a motor is not usually
advisable. As a general rule, assume that if you do
it, you will burn out the pot. If the motor draws
less current than the pot can handle, that's ok, but
you need to know that up front.

If you use a pot to drive a transistor, you can
control a lot more current:

V+ ---+----[Motor]----+
| |
P /c
O<---[220R]---| NPN Power xsistor
T \e
| |
Gnd ---+---------------+


The NPN transistor needs to be able to handle the
power and current that the motor needs.


---

V+ ---+---------------+
| |
P /c
O<------------| NPN Power xsistor
T \e
| |
Gnd --+---[Motor]-----+

Better, yes?

Yes!

But you've ended my plan to gain world domination
by the acquisition of all of the 220 ohm resistor
factories.

Ed

 

[ehsjr]

Michael A. Terrell wrote:

ehsjr wrote:

Michael A. Terrell wrote:

ehsjr wrote:


Michael A. Terrell wrote:


John Fields wrote:



Still, it's not a bad idea and will allow Ed to maintain his
stranglehold on the world's supply of 220 ohm resistors.

He better get busy. It lookks like I have over 10,000 on hand.

http://home.earthlink.net/~mike.terrell/Epres.html

Curses ... foiled again!



Do you want a really good deal on them?



Thanks, but I expect we share a problem:
inventory > space
That's why my plan was to acquire factories.



You haven't heard my offer, yet!

You haven't seen my "available" space yet!

Maybe you could make a resistor sculpture of a
horse, a la Ocala Horse Fever? I still enjoy
those pictures you pointed out.

Ed

 

[Michael A. Terrell]

John Fields wrote:

On Mon, 18 Feb 2008 20:24:12 GMT, ehsjr <ehsjr@bellatlantic.net
wrote:

kayvee wrote:
I have a 500k ohm POT and I will be using it to vary the voltage of a
circuit I am making. It is basically a motor which I want to be able
to change the voltage drop across it. I will be connecting it in
series with the motor. This POT I have has 3 lead coming off of it. I
am under the impression that if I connect the middle lead and one of
the outer leads it will vary the current of the circuit, and if I
connect all 3 lead in a curtain fashion it will vary the voltage.

Now my question is how do I connect the 3 leads?

I have tried reading explanations, I would appreciate a straight
forward good old fashioned diagram.

[POT}
| | |
? ? ?

*---[DC]----?---------[MOTOR]---*
| |
| |
*-------------------------------*

Connecting a pot directly to a motor is not usually
advisable. As a general rule, assume that if you do
it, you will burn out the pot. If the motor draws
less current than the pot can handle, that's ok, but
you need to know that up front.

If you use a pot to drive a transistor, you can
control a lot more current:

V+ ---+----[Motor]----+
| |
P /c
O<---[220R]---| NPN Power xsistor
T \e
| |
Gnd ---+---------------+


The NPN transistor needs to be able to handle the
power and current that the motor needs.

---

V+ ---+---------------+
| |
P /c
O<------------| NPN Power xsistor
T \e
| |
Gnd --+---[Motor]-----+

Better, yes?

Unless you turn the wiper all the way to the top terminal and destroy
the transistor. A resistor to limits the base current to a safe level
should be added between that terminal and V+. (For once I got to make
the correction before John caught it) ;-)



--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[kayvee]

On Feb 18, 6:22 pm, John Fields <jfie...@austininstruments.com> wrote:

On Mon, 18 Feb 2008 20:24:12 GMT, ehsjr <eh...@bellatlantic.net
wrote:



kayvee wrote:
I have a 500k ohm POT and I will be using it to vary the voltage of a
circuit I am making. It is basically a motor which I want to be able
to change the voltage drop across it. I will be connecting it in
series with the motor. This POT I have has 3 lead coming off of it. I
am under the impression that if I connect the middle lead and one of
the outer leads it will vary the current of the circuit, and if I
connect all 3 lead in a curtain fashion it will vary the voltage.

Now my question is how do I connect the 3 leads?

I have tried reading explanations, I would appreciate a straight
forward good old fashioned diagram.

[POT}
| | |
? ? ?

*---[DC]----?---------[MOTOR]---*
| |
| |
*-------------------------------*

Connecting a pot directly to a motor is not usually
advisable. As a general rule, assume that if you do
it, you will burn out the pot. If the motor draws
less current than the pot can handle, that's ok, but
you need to know that up front.

If you use a pot to drive a transistor, you can
control a lot more current:

V+ ---+----[Motor]----+
| |
P /c
O<---[220R]---| NPN Power xsistor
T \e
| |
Gnd ---+---------------+

The NPN transistor needs to be able to handle the
power and current that the motor needs.

---

V+ ---+---------------+
| |
P /c
O<------------| NPN Power xsistor
T \e
| |
Gnd --+---[Motor]-----+

Better, yes?

--
JF

Oh, that seems pretty clear. Thanks for the explanation. I'll put an
NPN and see what happens.

 

[Michael A. Terrell]

ehsjr wrote:

Michael A. Terrell wrote:

You haven't heard my offer, yet!


You haven't seen my "available" space yet!

I'll put up my lack of free space against yours, any day.

I had to put five printers in the garden shed today, so it wouldn't
rain on them while I was gone. I have stopped refurbishing computers
for a while to attack the problem from the other end. I'm doing triage,
and separating the rebuildable from the hopeless.

I put the hopeless units in the dimbulb pile so they can be ripped
apart for salvage. I can only give away so many win 95 computers to
preschoolers.

The ones that work, or almost work will soon be in use at their new
home in a daycare center.

Maybe you could make a resistor sculpture of a
horse, a la Ocala Horse Fever? I still enjoy
those pictures you pointed out.

WHAT???????????????? Use up my good 63/37 solder to build model
horses? NEVER!!!!!!!!!!!!!!! They will have to pry my lead based
solder out of my cold, dead hands!

;-)

BTW, I think they may do another batch of those horses. If they do,
I'll try top remember to post a link. the Ocala Star banner did a
recent series called Barchitecture. where the whole series was built
around dogs. I can't find it online right now, but I'll see if I can
locate a working link. It was published as a section of the newspaper.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[John Fields]

On Mon, 18 Feb 2008 20:24:12 GMT, ehsjr <ehsjr@bellatlantic.net>
wrote:

kayvee wrote:
I have a 500k ohm POT and I will be using it to vary the voltage of a
circuit I am making. It is basically a motor which I want to be able
to change the voltage drop across it. I will be connecting it in
series with the motor. This POT I have has 3 lead coming off of it. I
am under the impression that if I connect the middle lead and one of
the outer leads it will vary the current of the circuit, and if I
connect all 3 lead in a curtain fashion it will vary the voltage.

Now my question is how do I connect the 3 leads?

I have tried reading explanations, I would appreciate a straight
forward good old fashioned diagram.

[POT}
| | |
? ? ?

*---[DC]----?---------[MOTOR]---*
| |
| |
*-------------------------------*

Connecting a pot directly to a motor is not usually
advisable. As a general rule, assume that if you do
it, you will burn out the pot. If the motor draws
less current than the pot can handle, that's ok, but
you need to know that up front.

If you use a pot to drive a transistor, you can
control a lot more current:

V+ ---+----[Motor]----+
| |
P /c
O<---[220R]---| NPN Power xsistor
T \e
| |
Gnd ---+---------------+


The NPN transistor needs to be able to handle the
power and current that the motor needs.

---

V+ ---+---------------+
| |
P /c
O<------------| NPN Power xsistor
T \e
| |
Gnd --+---[Motor]-----+

Better, yes?

--
JF

 

[ehsjr]

kayvee wrote:

I have a 500k ohm POT and I will be using it to vary the voltage of a
circuit I am making. It is basically a motor which I want to be able
to change the voltage drop across it. I will be connecting it in
series with the motor. This POT I have has 3 lead coming off of it. I
am under the impression that if I connect the middle lead and one of
the outer leads it will vary the current of the circuit, and if I
connect all 3 lead in a curtain fashion it will vary the voltage.

Now my question is how do I connect the 3 leads?

I have tried reading explanations, I would appreciate a straight
forward good old fashioned diagram.

[POT}
| | |
? ? ?

*---[DC]----?---------[MOTOR]---*
| |
| |
*-------------------------------*

Connecting a pot directly to a motor is not usually
advisable. As a general rule, assume that if you do
it, you will burn out the pot. If the motor draws
less current than the pot can handle, that's ok, but
you need to know that up front.

If you use a pot to drive a transistor, you can
control a lot more current:

V+ ---+----[Motor]----+
| |
P /c
O<---[220R]---| NPN Power xsistor
T \e
| |
Gnd ---+---------------+


The NPN transistor needs to be able to handle the
power and current that the motor needs.

Ed

 

On Feb 18, 12:38 am, John Popelish <jpopel...@rica.net> wrote:

kayvee wrote:
I have a 500k ohm POT and I will be using it to vary the voltage of a
circuit I am making. It is basically a motor which I want to be able
to change the voltage drop across it. I will be connecting it in
series with the motor. This POT I have has 3 lead coming off of it. I
am under the impression that if I connect the middle lead and one of
the outer leads it will vary the current of the circuit, and if I
connect all 3 lead in a curtain fashion it will vary the voltage.

Now my question is how do I connect the 3 leads?

I have tried reading explanations, I would appreciate a straight
forward good old fashioned diagram.

[POT}
| | |
? ? ?

*---[DC]----?---------[MOTOR]---*
| |
| |
*-------------------------------*

Inside the pot is a resistor with a connection to each end
(the outer terminals) and a sliding contact (the center
terminal

* ,--/\/\/\/\--,
* | ^ |
* | | |
* 0 0 0

If you want to insert a variable resistor in series with the
motor, use one end terminal and the center terminal to
complete the motor circuit.

* [POT}
* | | |
* | |
* *---[DC]---* *--------[MOTOR]---*
* | |
* | |
* *-------------------------------*

Unfortunately, a 500k ohm pot has so much resistance that
the motor will stop the moment you slide in even the tiniest
part of the rotation, and may burn a hole in the resistive
element at the end. You might try something like a 1k pot
or a 100 ohm pot. If you have some fixed resistors you can
try a few of them and get an idea what resistance is close
to doing what you want.

--
Regards,

John Popelish

Thanks, John. I'll pick myself up a 1k ohm or a 100 ohm pot today and
give it a try!

 

[John Popelish]

kayvee wrote:

I have a 500k ohm POT and I will be using it to vary the voltage of a
circuit I am making. It is basically a motor which I want to be able
to change the voltage drop across it. I will be connecting it in
series with the motor. This POT I have has 3 lead coming off of it. I
am under the impression that if I connect the middle lead and one of
the outer leads it will vary the current of the circuit, and if I
connect all 3 lead in a curtain fashion it will vary the voltage.

Now my question is how do I connect the 3 leads?

I have tried reading explanations, I would appreciate a straight
forward good old fashioned diagram.

[POT}
| | |
? ? ?

*---[DC]----?---------[MOTOR]---*
| |
| |
*-------------------------------*

Inside the pot is a resistor with a connection to each end
(the outer terminals) and a sliding contact (the center
terminal>

* ,--/\/\/\/\--,
* | ^ |
* | | |
* 0 0 0

If you want to insert a variable resistor in series with the
motor, use one end terminal and the center terminal to
complete the motor circuit.

* [POT}
* | | |
* | |
* *---[DC]---* *--------[MOTOR]---*
* | |
* | |
* *-------------------------------*

Unfortunately, a 500k ohm pot has so much resistance that
the motor will stop the moment you slide in even the tiniest
part of the rotation, and may burn a hole in the resistive
element at the end. You might try something like a 1k pot
or a 100 ohm pot. If you have some fixed resistors you can
try a few of them and get an idea what resistance is close
to doing what you want.

--
Regards,

John Popelish

 

[kayvee]

I have a 500k ohm POT and I will be using it to vary the voltage of a
circuit I am making. It is basically a motor which I want to be able
to change the voltage drop across it. I will be connecting it in
series with the motor. This POT I have has 3 lead coming off of it. I
am under the impression that if I connect the middle lead and one of
the outer leads it will vary the current of the circuit, and if I
connect all 3 lead in a curtain fashion it will vary the voltage.

Now my question is how do I connect the 3 leads?

I have tried reading explanations, I would appreciate a straight
forward good old fashioned diagram.

[POT}
| | |
? ? ?

*---[DC]----?---------[MOTOR]---*
| |
| |
*-------------------------------*

 

[John Fields]

On Mon, 18 Feb 2008 23:55:09 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

John Fields wrote:

On Mon, 18 Feb 2008 20:24:12 GMT, ehsjr <ehsjr@bellatlantic.net
wrote:

kayvee wrote:
I have a 500k ohm POT and I will be using it to vary the voltage of a
circuit I am making. It is basically a motor which I want to be able
to change the voltage drop across it. I will be connecting it in
series with the motor. This POT I have has 3 lead coming off of it. I
am under the impression that if I connect the middle lead and one of
the outer leads it will vary the current of the circuit, and if I
connect all 3 lead in a curtain fashion it will vary the voltage.

Now my question is how do I connect the 3 leads?

I have tried reading explanations, I would appreciate a straight
forward good old fashioned diagram.

[POT}
| | |
? ? ?

*---[DC]----?---------[MOTOR]---*
| |
| |
*-------------------------------*

Connecting a pot directly to a motor is not usually
advisable. As a general rule, assume that if you do
it, you will burn out the pot. If the motor draws
less current than the pot can handle, that's ok, but
you need to know that up front.

If you use a pot to drive a transistor, you can
control a lot more current:

V+ ---+----[Motor]----+
| |
P /c
O<---[220R]---| NPN Power xsistor
T \e
| |
Gnd ---+---------------+


The NPN transistor needs to be able to handle the
power and current that the motor needs.

---

V+ ---+---------------+
| |
P /c
O<------------| NPN Power xsistor
T \e
| |
Gnd --+---[Motor]-----+

Better, yes?



Unless you turn the wiper all the way to the top terminal and destroy
the transistor. A resistor to limits the base current to a safe level
should be added between that terminal and V+. (For once I got to make
the correction before John caught it) ;-)

---
Since the circuit is an emitter follower, the voltage dropped across
the motor will cause the emitter voltage to rise as the base voltage
is increased, which will limit the base current to whatever's needed
to keep the base enough more positive than the emitter to allow more
and more current into the motor as the pot is rotated.

Still, it's not a bad idea and will allow Ed to maintain his
stranglehold on the world's supply of 220 ohm resistors.

Also, this may not be a bad idea:

..V+>---+---------------+
.. | |
.. [220] |
.. | |
.. P /c
.. O<------------| NPN Power xsistor
.. T \e
.. | |
.. +---[Motor]-----+
.. | |
..GND>--+---[Diode>]----+

--
JF

 

[kayvee]

On Feb 22, 6:06 pm, John Fields <jfie...@austininstruments.com> wrote:

On Mon, 18 Feb 2008 23:55:09 -0500, "Michael A. Terrell"



mike.terr...@earthlink.net> wrote:
John Fields wrote:

On Mon, 18 Feb 2008 20:24:12 GMT, ehsjr <eh...@bellatlantic.net
wrote:

kayvee wrote:
I have a 500k ohm POT and I will be using it to vary the voltage of a
circuit I am making. It is basically a motor which I want to be able
to change the voltage drop across it. I will be connecting it in
series with the motor. This POT I have has 3 lead coming off of it. I
am under the impression that if I connect the middle lead and one of
the outer leads it will vary the current of the circuit, and if I
connect all 3 lead in a curtain fashion it will vary the voltage.

Now my question is how do I connect the 3 leads?

I have tried reading explanations, I would appreciate a straight
forward good old fashioned diagram.

[POT}
| | |
? ? ?

*---[DC]----?---------[MOTOR]---*
| |
| |
*-------------------------------*

Connecting a pot directly to a motor is not usually
advisable. As a general rule, assume that if you do
it, you will burn out the pot. If the motor draws
less current than the pot can handle, that's ok, but
you need to know that up front.

If you use a pot to drive a transistor, you can
control a lot more current:

V+ ---+----[Motor]----+
| |
P /c
O<---[220R]---| NPN Power xsistor
T \e
| |
Gnd ---+---------------+

The NPN transistor needs to be able to handle the
power and current that the motor needs.

---

V+ ---+---------------+
| |
P /c
O<------------| NPN Power xsistor
T \e
| |
Gnd --+---[Motor]-----+

Better, yes?

Unless you turn the wiper all the way to the top terminal and destroy
the transistor. A resistor to limits the base current to a safe level
should be added between that terminal and V+. (For once I got to make
the correction before John caught it) ;-)

---
Since the circuit is an emitter follower, the voltage dropped across
the motor will cause the emitter voltage to rise as the base voltage
is increased, which will limit the base current to whatever's needed
to keep the base enough more positive than the emitter to allow more
and more current into the motor as the pot is rotated.

Still, it's not a bad idea and will allow Ed to maintain his
stranglehold on the world's supply of 220 ohm resistors.

Also, this may not be a bad idea:

.V+>---+---------------+
. | |
. [220] |
. | |
. P /c
. O<------------| NPN Power xsistor
. T \e
. | |
. +---[Motor]-----+
. | |
.GND>--+---[Diode>]----+

--
JF

Thanks for all the help. But what purpose does the diode serve?

 

[Michael A. Terrell]

kayvee wrote:

Thanks for all the help. But what purpose does the diode serve?

The motor has back EMF, and can damage the transistor. The diode is
used to shunt it.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[John Popelish]

kayvee wrote:

On Feb 22, 6:06 pm, John Fields <jfie...@austininstruments.com> wrote:

.V+>---+---------------+
. | |
. [220] |
. | |
. P /c
. O<------------| NPN Power xsistor
. T \e
. | |
. +---[Motor]-----+
. | |
.GND>--+---[Diode>]----+

--
JF

Thanks for all the help. But what purpose does the diode serve?

It is intended to pass motor current, limiting the voltage
the motor's inductance generates, if the pot wiper happens
to slide over a bad spot, opening up the base, while the
motor is running. With it there, the most negative that
inductive current can drive the emitter voltage is one diode
drop more negative than the ground rail. If the to could be
guaranteed to never go over a speck of dust, etc., you could
do without it.

--
Regards,

John Popelish

 

[Michael A. Terrell]

John Fields wrote:

On Mon, 18 Feb 2008 23:55:09 -0500, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

John Fields wrote:

On Mon, 18 Feb 2008 20:24:12 GMT, ehsjr <ehsjr@bellatlantic.net
wrote:

kayvee wrote:
I have a 500k ohm POT and I will be using it to vary the voltage of a
circuit I am making. It is basically a motor which I want to be able
to change the voltage drop across it. I will be connecting it in
series with the motor. This POT I have has 3 lead coming off of it. I
am under the impression that if I connect the middle lead and one of
the outer leads it will vary the current of the circuit, and if I
connect all 3 lead in a curtain fashion it will vary the voltage.

Now my question is how do I connect the 3 leads?

I have tried reading explanations, I would appreciate a straight
forward good old fashioned diagram.

[POT}
| | |
? ? ?

*---[DC]----?---------[MOTOR]---*
| |
| |
*-------------------------------*

Connecting a pot directly to a motor is not usually
advisable. As a general rule, assume that if you do
it, you will burn out the pot. If the motor draws
less current than the pot can handle, that's ok, but
you need to know that up front.

If you use a pot to drive a transistor, you can
control a lot more current:

V+ ---+----[Motor]----+
| |
P /c
O<---[220R]---| NPN Power xsistor
T \e
| |
Gnd ---+---------------+


The NPN transistor needs to be able to handle the
power and current that the motor needs.

---

V+ ---+---------------+
| |
P /c
O<------------| NPN Power xsistor
T \e
| |
Gnd --+---[Motor]-----+

Better, yes?



Unless you turn the wiper all the way to the top terminal and destroy
the transistor. A resistor to limits the base current to a safe level
should be added between that terminal and V+. (For once I got to make
the correction before John caught it) ;-)

---
Since the circuit is an emitter follower, the voltage dropped across
the motor will cause the emitter voltage to rise as the base voltage
is increased, which will limit the base current to whatever's needed
to keep the base enough more positive than the emitter to allow more
and more current into the motor as the pot is rotated.

Still, it's not a bad idea and will allow Ed to maintain his
stranglehold on the world's supply of 220 ohm resistors.

he better get busy. It lookks like I have over 10,000 on hand.

http://home.earthlink.net/~mike.terrell/Epres.html

Also, this may not be a bad idea:

.V+>---+---------------+
. | |
. [220] |
. | |
. P /c
. O<------------| NPN Power xsistor
. T \e
. | |
. +---[Motor]-----+
. | |
.GND>--+---[Diode>]----+

--
JF

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[ehsjr]

Michael A. Terrell wrote:

John Fields wrote:

On Mon, 18 Feb 2008 23:55:09 -0500, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


John Fields wrote:

On Mon, 18 Feb 2008 20:24:12 GMT, ehsjr <ehsjr@bellatlantic.net
wrote:


kayvee wrote:

I have a 500k ohm POT and I will be using it to vary the voltage of a
circuit I am making. It is basically a motor which I want to be able
to change the voltage drop across it. I will be connecting it in
series with the motor. This POT I have has 3 lead coming off of it. I
am under the impression that if I connect the middle lead and one of
the outer leads it will vary the current of the circuit, and if I
connect all 3 lead in a curtain fashion it will vary the voltage.

Now my question is how do I connect the 3 leads?

I have tried reading explanations, I would appreciate a straight
forward good old fashioned diagram.

[POT}
| | |
? ? ?

*---[DC]----?---------[MOTOR]---*
| |
| |
*-------------------------------*

Connecting a pot directly to a motor is not usually
advisable. As a general rule, assume that if you do
it, you will burn out the pot. If the motor draws
less current than the pot can handle, that's ok, but
you need to know that up front.

If you use a pot to drive a transistor, you can
control a lot more current:

V+ ---+----[Motor]----+
| |
P /c
O<---[220R]---| NPN Power xsistor
T \e
| |
Gnd ---+---------------+


The NPN transistor needs to be able to handle the
power and current that the motor needs.

---

V+ ---+---------------+
| |
P /c
O<------------| NPN Power xsistor
T \e
| |
Gnd --+---[Motor]-----+

Better, yes?



Unless you turn the wiper all the way to the top terminal and destroy
the transistor. A resistor to limits the base current to a safe level
should be added between that terminal and V+. (For once I got to make
the correction before John caught it) ;-)

---
Since the circuit is an emitter follower, the voltage dropped across
the motor will cause the emitter voltage to rise as the base voltage
is increased, which will limit the base current to whatever's needed
to keep the base enough more positive than the emitter to allow more
and more current into the motor as the pot is rotated.

Still, it's not a bad idea and will allow Ed to maintain his
stranglehold on the world's supply of 220 ohm resistors.



he better get busy. It lookks like I have over 10,000 on hand.

http://home.earthlink.net/~mike.terrell/Epres.html

Curses ... foiled again!

Ed

Also, this may not be a bad idea:

.V+>---+---------------+
. | |
. [220] |
. | |
. P /c
. O<------------| NPN Power xsistor
. T \e
. | |
. +---[Motor]-----+
. | |
.GND>--+---[Diode>]----+

--
JF

 

[Michael A. Terrell]

ehsjr wrote:

Michael A. Terrell wrote:
John Fields wrote:

Still, it's not a bad idea and will allow Ed to maintain his
stranglehold on the world's supply of 220 ohm resistors.

He better get busy. It lookks like I have over 10,000 on hand.

http://home.earthlink.net/~mike.terrell/Epres.html

Curses ... foiled again!

Do you want a really good deal on them?


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[ehsjr]

Michael A. Terrell wrote:

ehsjr wrote:

Michael A. Terrell wrote:

John Fields wrote:


Still, it's not a bad idea and will allow Ed to maintain his
stranglehold on the world's supply of 220 ohm resistors.

He better get busy. It lookks like I have over 10,000 on hand.

http://home.earthlink.net/~mike.terrell/Epres.html

Curses ... foiled again!



Do you want a really good deal on them?

Thanks, but I expect we share a problem:
inventory > space
That's why my plan was to acquire factories.

Ed

 

[Michael A. Terrell]

ehsjr wrote:

Michael A. Terrell wrote:
ehsjr wrote:

Michael A. Terrell wrote:

John Fields wrote:


Still, it's not a bad idea and will allow Ed to maintain his
stranglehold on the world's supply of 220 ohm resistors.

He better get busy. It lookks like I have over 10,000 on hand.

http://home.earthlink.net/~mike.terrell/Epres.html

Curses ... foiled again!



Do you want a really good deal on them?



Thanks, but I expect we share a problem:
inventory > space
That's why my plan was to acquire factories.

You haven't heard my offer, yet!

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida