What range should my POT be?

[kayvee]

Okay, so I have this motor and it is powered by a 24VDC power supply,
and I would like to vary the voltage going to this motor. This motor
draws 0.4A with 24V. I understand that connecting a pot normally to
this motor will burn out the pot rather quickly, so one must use a NPN
transistor. I reckon in this fashion:


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

Two questions: Is this a good hookup? And, what would be a good range
for the pot?

Thanks again everybody!

 

[Sjouke Burry]

kayvee wrote:

Okay, so I have this motor and it is powered by a 24VDC power supply,
and I would like to vary the voltage going to this motor. This motor
draws 0.4A with 24V. I understand that connecting a pot normally to
this motor will burn out the pot rather quickly, so one must use a NPN
transistor. I reckon in this fashion:


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

Two questions: Is this a good hookup? And, what would be a good range
for the pot?

Thanks again everybody!

Use a darlington for the transistor, and a 1K pot.

 

[JeffM]

kayvee wrote:

powered by a 24VDC power supply,
and I would like to vary the voltage going to this motor[...]

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

[...]Is this a good hookup?

Investigate this concept instead:

http://groups.google.com/search?q=pulse-width-modulator+OR+pulse-width-modulation+torque&qt_s=Search+Groups&num=100

 

[Paul E. Schoen]

"Sjouke Burry" <burrynulnulfour@ppllaanneett.nnlll> wrote in message
news:4927a7e1$0$27216$ba620dc5@text.nova.planet.nl...

kayvee wrote:
Okay, so I have this motor and it is powered by a 24VDC power supply,
and I would like to vary the voltage going to this motor. This motor
draws 0.4A with 24V. I understand that connecting a pot normally to
this motor will burn out the pot rather quickly, so one must use a NPN
transistor. I reckon in this fashion:


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

Two questions: Is this a good hookup? And, what would be a good range
for the pot?

Thanks again everybody!

Use a darlington for the transistor, and a 1K pot.

For 24 VDC it needs to be a 1 watt pot. And a diode across the motor might
be needed to absorb back EMF (DC generation) as it slows down.

Paul

 

[John Larkin]

On Sat, 22 Nov 2008 07:34:10 +0100, Sjouke Burry
<burrynulnulfour@ppllaanneett.nnlll> wrote:

kayvee wrote:
Okay, so I have this motor and it is powered by a 24VDC power supply,
and I would like to vary the voltage going to this motor. This motor
draws 0.4A with 24V. I understand that connecting a pot normally to
this motor will burn out the pot rather quickly, so one must use a NPN
transistor. I reckon in this fashion:


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

Two questions: Is this a good hookup? And, what would be a good range
for the pot?

Thanks again everybody!

Use a darlington for the transistor, and a 1K pot.

That will run sorta hot. 5K is reasonable with a darlington.

John

 

[Bob Monsen]

"kayvee" <kmvgroups@gmail.com> wrote in message
news:eb553355-7ceb-4d01-87cb-b79c2ea6ac61@f20g2000yqg.googlegroups.com...

Okay, so I have this motor and it is powered by a 24VDC power supply,
and I would like to vary the voltage going to this motor. This motor
draws 0.4A with 24V. I understand that connecting a pot normally to
this motor will burn out the pot rather quickly, so one must use a NPN
transistor. I reckon in this fashion:


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

Two questions: Is this a good hookup? And, what would be a good range
for the pot?

Thanks again everybody!

For .4A, a 2.2k pot would probably work fine. You also need a diode in
parallel with the motor, pointing up. That will carry any current due to
starting and stopping the motor, preventing it from eating your transistor
with a voltage transient.

Also, I would probably use another NPN transistor in a darlington
configuration (as suggested by Sjouke Burry). If you use the extra
transistor, you can use a much smaller pot, like 10k, which will be cooler
with a 24V supply:

So, the full circuit would look like this:

24V------o-------o--------.
| | |
| | |
.-. |/ |
10k | |<---| 2N4401 |
| | |> |
'-' | |
| | |/
| o------| 2N3055
| | |>
| | |
| | 1k_ |
| '--|___|-o
| |
| .--------o
| | |
| | .---o----.
| - | |
| ^ | motor |
| 1N4001 | |
| | '---o----'
| | |
| | |
GND--------o-------o--------'
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

Here is a simulation using LTSpice for your amusement. Note that the power
through the 2N3055 is going to be about 2.4W at the maximum point, so you
may need a heat sink.

You can download LTSpice from http://www.linear.com/software

It is quite fun to try things out with, but don't believe it too much;
always use prototyping as well.

-------- pot-motor.asc --------
Version 4
SHEET 1 880 680
WIRE 144 32 0 32
WIRE 352 32 144 32
WIRE 480 32 352 32
WIRE 144 64 144 32
WIRE 352 64 352 32
WIRE 288 112 192 112
WIRE 480 128 480 32
WIRE 352 176 352 160
WIRE 416 176 352 176
WIRE 352 192 352 176
WIRE 352 208 352 192
WIRE 0 240 0 32
WIRE 480 272 480 224
WIRE 480 272 352 272
WIRE 480 304 480 272
WIRE 352 320 352 272
WIRE 0 400 0 320
WIRE 144 400 144 144
WIRE 144 400 0 400
WIRE 352 400 352 384
WIRE 352 400 144 400
WIRE 480 400 480 384
WIRE 480 400 352 400
FLAG 0 400 0
SYMBOL voltage 0 224 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24
SYMBOL npn 416 128 R0
SYMATTR InstName Q1
SYMATTR Value 2N3055
SYMBOL res 464 288 R0
SYMATTR InstName R1
SYMATTR Value {24/.4}
SYMBOL potentiometer 128 48 R0
WINDOW 3 -72 140 Left 0
SYMATTR Value Rtot=10K wiper={X}
SYMATTR InstName U1
SYMBOL npn 288 64 R0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL diode 368 384 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value 1N914
SYMBOL res 368 288 R180
WINDOW 0 36 76 Left 0
WINDOW 3 36 40 Left 0
SYMATTR InstName R2
SYMATTR Value 1k
TEXT -32 424 Left 0 !.op
TEXT -48 472 Left 0 !.step param X .1 .9 .1
------------ end of pot-motor.asc ----------------------

 

[kayvee]

On Nov 22, 1:39 pm, "Bob Monsen" <robertmon...@sbcglobal.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message

news:eb553355-7ceb-4d01-87cb-b79c2ea6ac61@f20g2000yqg.googlegroups.com...



Okay, so I have this motor and it is powered by a 24VDC power supply,
and I would like to vary the voltage going to this motor. This motor
draws 0.4A with 24V. I understand that connecting a pot normally to
this motor will burn out the pot rather quickly, so one must use a NPN
transistor. I reckon in this fashion:

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

Two questions: Is this a good hookup? And, what would be a good range
for the pot?

Thanks again everybody!

For .4A, a 2.2k pot would probably work fine. You also need a diode in
parallel with the motor, pointing up. That will carry any current due to
starting and stopping the motor, preventing it from eating your transistor
with a voltage transient.

Also, I would probably use another NPN transistor in a darlington
configuration (as suggested by Sjouke Burry). If you use the extra
transistor, you can use a much smaller pot, like 10k, which will be cooler
with a 24V supply:

So, the full circuit would look like this:

  24V------o-------o--------.
           |       |        |
           |       |        |
          .-.    |/         |
     10k  | |<---|  2N4401  |
          | |    |>         |
          '-'      |        |
           |       |      |/
           |       o------|  2N3055
           |       |      |
           |       |        |
           |       |   1k_  |
           |       '--|___|-o
           |                |
           |       .--------o
           |       |        |
           |       |    .---o----.
           |       -    |        |
           |       ^    | motor  |
           |  1N4001    |        |
           |       |    '---o----'
           |       |        |
           |       |        |
GND--------o-------o--------'
(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

Here is a simulation using LTSpice for your amusement. Note that the power
through the 2N3055 is going to be about 2.4W at the maximum point, so you
may need a heat sink.

You can download LTSpice fromhttp://www.linear.com/software

It is quite fun to try things out with, but don't believe it too much;
always use prototyping as well.

-------- pot-motor.asc --------
Version 4
SHEET 1 880 680
WIRE 144 32 0 32
WIRE 352 32 144 32
WIRE 480 32 352 32
WIRE 144 64 144 32
WIRE 352 64 352 32
WIRE 288 112 192 112
WIRE 480 128 480 32
WIRE 352 176 352 160
WIRE 416 176 352 176
WIRE 352 192 352 176
WIRE 352 208 352 192
WIRE 0 240 0 32
WIRE 480 272 480 224
WIRE 480 272 352 272
WIRE 480 304 480 272
WIRE 352 320 352 272
WIRE 0 400 0 320
WIRE 144 400 144 144
WIRE 144 400 0 400
WIRE 352 400 352 384
WIRE 352 400 144 400
WIRE 480 400 480 384
WIRE 480 400 352 400
FLAG 0 400 0
SYMBOL voltage 0 224 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24
SYMBOL npn 416 128 R0
SYMATTR InstName Q1
SYMATTR Value 2N3055
SYMBOL res 464 288 R0
SYMATTR InstName R1
SYMATTR Value {24/.4}
SYMBOL potentiometer 128 48 R0
WINDOW 3 -72 140 Left 0
SYMATTR Value Rtot=10K wiper={X}
SYMATTR InstName U1
SYMBOL npn 288 64 R0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL diode 368 384 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value 1N914
SYMBOL res 368 288 R180
WINDOW 0 36 76 Left 0
WINDOW 3 36 40 Left 0
SYMATTR InstName R2
SYMATTR Value 1k
TEXT -32 424 Left 0 !.op
TEXT -48 472 Left 0 !.step param X .1 .9 .1
------------ end of pot-motor.asc ----------------------

I think that circuit would be perfect. I think I have all the
necessary parts at home. I'll try it out soon and tell you how it goes!

 

[kayvee]

On Nov 22, 1:39 pm, "Bob Monsen" <robertmon...@sbcglobal.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message

news:eb553355-7ceb-4d01-87cb-b79c2ea6ac61@f20g2000yqg.googlegroups.com...



Okay, so I have this motor and it is powered by a 24VDC power supply,
and I would like to vary the voltage going to this motor. This motor
draws 0.4A with 24V. I understand that connecting a pot normally to
this motor will burn out the pot rather quickly, so one must use a NPN
transistor. I reckon in this fashion:

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

Two questions: Is this a good hookup? And, what would be a good range
for the pot?

Thanks again everybody!

For .4A, a 2.2k pot would probably work fine. You also need a diode in
parallel with the motor, pointing up. That will carry any current due to
starting and stopping the motor, preventing it from eating your transistor
with a voltage transient.

Also, I would probably use another NPN transistor in a darlington
configuration (as suggested by Sjouke Burry). If you use the extra
transistor, you can use a much smaller pot, like 10k, which will be cooler
with a 24V supply:

So, the full circuit would look like this:

24V------o-------o--------.
| | |
| | |
.-. |/ |
10k | |<---| 2N4401 |
| | |> |
'-' | |
| | |/
| o------| 2N3055
| | |
| | |
| | 1k_ |
| '--|___|-o
| |
| .--------o
| | |
| | .---o----.
| - | |
| ^ | motor |
| 1N4001 | |
| | '---o----'
| | |
| | |
GND--------o-------o--------'
(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

Here is a simulation using LTSpice for your amusement. Note that the power
through the 2N3055 is going to be about 2.4W at the maximum point, so you
may need a heat sink.

You can download LTSpice fromhttp://www.linear.com/software

It is quite fun to try things out with, but don't believe it too much;
always use prototyping as well.

-------- pot-motor.asc --------
Version 4
SHEET 1 880 680
WIRE 144 32 0 32
WIRE 352 32 144 32
WIRE 480 32 352 32
WIRE 144 64 144 32
WIRE 352 64 352 32
WIRE 288 112 192 112
WIRE 480 128 480 32
WIRE 352 176 352 160
WIRE 416 176 352 176
WIRE 352 192 352 176
WIRE 352 208 352 192
WIRE 0 240 0 32
WIRE 480 272 480 224
WIRE 480 272 352 272
WIRE 480 304 480 272
WIRE 352 320 352 272
WIRE 0 400 0 320
WIRE 144 400 144 144
WIRE 144 400 0 400
WIRE 352 400 352 384
WIRE 352 400 144 400
WIRE 480 400 480 384
WIRE 480 400 352 400
FLAG 0 400 0
SYMBOL voltage 0 224 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24
SYMBOL npn 416 128 R0
SYMATTR InstName Q1
SYMATTR Value 2N3055
SYMBOL res 464 288 R0
SYMATTR InstName R1
SYMATTR Value {24/.4}
SYMBOL potentiometer 128 48 R0
WINDOW 3 -72 140 Left 0
SYMATTR Value Rtot=10K wiper={X}
SYMATTR InstName U1
SYMBOL npn 288 64 R0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL diode 368 384 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value 1N914
SYMBOL res 368 288 R180
WINDOW 0 36 76 Left 0
WINDOW 3 36 40 Left 0
SYMATTR InstName R2
SYMATTR Value 1k
TEXT -32 424 Left 0 !.op
TEXT -48 472 Left 0 !.step param X .1 .9 .1
------------ end of pot-motor.asc ----------------------

Now I don't have a 2N3055 handy... But I do have an NPN - PMD16K100
Transistor laying around I could use. Would it be okay if I swapped
them? Here are the stats of the PMD16K100:

source: www.nteinc.com/specs/200to299/pdf/nte251.pdf

Absolute Maximum Ratings: (TA = +25°C unless otherwise specified)
Collector-Emitter Voltage,
VCEO . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 100Vb
Collector-Base Voltage,
VCB . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . .
100V
Emitter-Base Voltage,
VEB . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . .
5V
Collector Current, IC

Continuous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
20A

Peak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .. . . . . . . . . .
40A
Base Current,
IB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
500mA
Total Power Dissipation (TC = +25°C),
PD . . . . . . . . . . . . .. . . . . . . . . . 160W
Derate Above
25°C . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
0.915W/°C
Operating Junction Temperature Range,
TJ . . . . . . . . . . . . . .. . . . . . . . . -65° to +200°C
Storage Temperature Range,
Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -65° to
+200°C
Thermal Resistance, Junction-to-Case,
RthJC . . . . . . . . . . . . . . . . . . . . . 1.09°C/W

And here is the stats for the 2N3055 just for reference:

Source: http://www.onsemi.com/pub/Collateral/2N3055-D.PDF

Collector-Emitter Voltage VCEO 60 Vdc
Collector-Emitter Voltage VCER 70
Vdc
Collector-Base Voltage VCB 100 Vdc
Emitter-Base Voltage VEB 7
Vdc
Collector Current - Continuous IC 15 Adc
Base Current IB
7 Adc
Total Power Dissipation @ TC = 25°C PD 115 W
Derate Above 25°C 0.657
W/°C
Operating and Storage Junction
Temperature Range TJ, Tstg -65 to
+200°C

Thanks!

 

[ehsjr]

kayvee wrote:

On Nov 22, 1:39 pm, "Bob Monsen" <robertmon...@sbcglobal.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message

news:eb553355-7ceb-4d01-87cb-b79c2ea6ac61@f20g2000yqg.googlegroups.com...




Okay, so I have this motor and it is powered by a 24VDC power supply,
and I would like to vary the voltage going to this motor. This motor
draws 0.4A with 24V. I understand that connecting a pot normally to
this motor will burn out the pot rather quickly, so one must use a NPN
transistor. I reckon in this fashion:

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

Two questions: Is this a good hookup? And, what would be a good range
for the pot?

Thanks again everybody!

For .4A, a 2.2k pot would probably work fine. You also need a diode in
parallel with the motor, pointing up. That will carry any current due to
starting and stopping the motor, preventing it from eating your transistor
with a voltage transient.

Also, I would probably use another NPN transistor in a darlington
configuration (as suggested by Sjouke Burry). If you use the extra
transistor, you can use a much smaller pot, like 10k, which will be cooler
with a 24V supply:

So, the full circuit would look like this:

24V------o-------o--------.
| | |
| | |
.-. |/ |
10k | |<---| 2N4401 |
| | |> |
'-' | |
| | |/
| o------| 2N3055
| | |
| | |
| | 1k_ |
| '--|___|-o
| |
| .--------o
| | |
| | .---o----.
| - | |
| ^ | motor |
| 1N4001 | |
| | '---o----'
| | |
| | |
GND--------o-------o--------'
(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

Here is a simulation using LTSpice for your amusement. Note that the power
through the 2N3055 is going to be about 2.4W at the maximum point, so you
may need a heat sink.

You can download LTSpice fromhttp://www.linear.com/software

It is quite fun to try things out with, but don't believe it too much;
always use prototyping as well.

-------- pot-motor.asc --------
Version 4
SHEET 1 880 680
WIRE 144 32 0 32
WIRE 352 32 144 32
WIRE 480 32 352 32
WIRE 144 64 144 32
WIRE 352 64 352 32
WIRE 288 112 192 112
WIRE 480 128 480 32
WIRE 352 176 352 160
WIRE 416 176 352 176
WIRE 352 192 352 176
WIRE 352 208 352 192
WIRE 0 240 0 32
WIRE 480 272 480 224
WIRE 480 272 352 272
WIRE 480 304 480 272
WIRE 352 320 352 272
WIRE 0 400 0 320
WIRE 144 400 144 144
WIRE 144 400 0 400
WIRE 352 400 352 384
WIRE 352 400 144 400
WIRE 480 400 480 384
WIRE 480 400 352 400
FLAG 0 400 0
SYMBOL voltage 0 224 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24
SYMBOL npn 416 128 R0
SYMATTR InstName Q1
SYMATTR Value 2N3055
SYMBOL res 464 288 R0
SYMATTR InstName R1
SYMATTR Value {24/.4}
SYMBOL potentiometer 128 48 R0
WINDOW 3 -72 140 Left 0
SYMATTR Value Rtot=10K wiper={X}
SYMATTR InstName U1
SYMBOL npn 288 64 R0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL diode 368 384 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value 1N914
SYMBOL res 368 288 R180
WINDOW 0 36 76 Left 0
WINDOW 3 36 40 Left 0
SYMATTR InstName R2
SYMATTR Value 1k
TEXT -32 424 Left 0 !.op
TEXT -48 472 Left 0 !.step param X .1 .9 .1
------------ end of pot-motor.asc ----------------------


Now I don't have a 2N3055 handy... But I do have an NPN - PMD16K100
Transistor laying around I could use. Would it be okay if I swapped
them? Here are the stats of the PMD16K100:

source: www.nteinc.com/specs/200to299/pdf/nte251.pdf

Absolute Maximum Ratings: (TA = +25°C unless otherwise specified)
Collector-Emitter Voltage,
VCEO . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 100Vb
Collector-Base Voltage,
VCB . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . .
100V
Emitter-Base Voltage,
VEB . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . .
5V
Collector Current, IC

Continuous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
20A

Peak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
40A
Base Current,
IB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
500mA
Total Power Dissipation (TC = +25°C),
PD . . . . . . . . . . . . .. . . . . . . . . . 160W
Derate Above
25°C . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
0.915W/°C
Operating Junction Temperature Range,
TJ . . . . . . . . . . . . . .. . . . . . . . . -65° to +200°C
Storage Temperature Range,
Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -65° to
+200°C
Thermal Resistance, Junction-to-Case,
RthJC . . . . . . . . . . . . . . . . . . . . . 1.09°C/W

And here is the stats for the 2N3055 just for reference:

Source: http://www.onsemi.com/pub/Collateral/2N3055-D.PDF

Collector-Emitter Voltage VCEO 60 Vdc
Collector-Emitter Voltage VCER 70
Vdc
Collector-Base Voltage VCB 100 Vdc
Emitter-Base Voltage VEB 7
Vdc
Collector Current - Continuous IC 15 Adc
Base Current IB
7 Adc
Total Power Dissipation @ TC = 25°C PD 115 W
Derate Above 25°C 0.657
W/°C
Operating and Storage Junction
Temperature Range TJ, Tstg -65 to
+200°C

Thanks!

You can use that. Just add a 4.7K resistor & diode
across the motor to your original:

V+ ---+---------------+
| |
P /c
O<---[4.7K]---| NPN PMD16K100
T \e
| |
+------>|-------+
| |
Gnd --+---[Motor]-----+

Ed

 

[kayvee]

On Nov 24, 8:11 pm, ehsjr <eh...@NOSPAMverizon.net> wrote:

kayvee wrote:
On Nov 22, 1:39 pm, "Bob Monsen" <robertmon...@sbcglobal.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message

news:eb553355-7ceb-4d01-87cb-b79c2ea6ac61@f20g2000yqg.googlegroups.com....

Okay, so I have this motor and it is powered by a 24VDC power supply,
and I would like to vary the voltage going to this motor. This motor
draws 0.4A with 24V. I understand that connecting a pot normally to
this motor will burn out the pot rather quickly, so one must use a NPN
transistor. I reckon in this fashion:

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

Two questions: Is this a good hookup? And, what would be a good range
for the pot?

Thanks again everybody!

For .4A, a 2.2k pot would probably work fine. You also need a diode in
parallel with the motor, pointing up. That will carry any current due to
starting and stopping the motor, preventing it from eating your transistor
with a voltage transient.

Also, I would probably use another NPN transistor in a darlington
configuration (as suggested by Sjouke Burry). If you use the extra
transistor, you can use a much smaller pot, like 10k, which will be cooler
with a 24V supply:

So, the full circuit would look like this:

 24V------o-------o--------.
          |       |        |
          |       |        |
         .-.    |/         |
    10k  | |<---|  2N4401  |
         | |    |>         |
         '-'      |        |
          |       |      |/
          |       o------|  2N3055
          |       |      |
          |       |        |
          |       |   1k_  |
          |       '--|___|-o
          |                |
          |       .--------o
          |       |        |
          |       |    .---o----.
          |       -    |        |
          |       ^    | motor  |
          |  1N4001    |        |
          |       |    '---o----'
          |       |        |
          |       |        |
GND--------o-------o--------'
(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

Here is a simulation using LTSpice for your amusement. Note that the power
through the 2N3055 is going to be about 2.4W at the maximum point, so you
may need a heat sink.

You can download LTSpice fromhttp://www.linear.com/software

It is quite fun to try things out with, but don't believe it too much;
always use prototyping as well.

-------- pot-motor.asc --------
Version 4
SHEET 1 880 680
WIRE 144 32 0 32
WIRE 352 32 144 32
WIRE 480 32 352 32
WIRE 144 64 144 32
WIRE 352 64 352 32
WIRE 288 112 192 112
WIRE 480 128 480 32
WIRE 352 176 352 160
WIRE 416 176 352 176
WIRE 352 192 352 176
WIRE 352 208 352 192
WIRE 0 240 0 32
WIRE 480 272 480 224
WIRE 480 272 352 272
WIRE 480 304 480 272
WIRE 352 320 352 272
WIRE 0 400 0 320
WIRE 144 400 144 144
WIRE 144 400 0 400
WIRE 352 400 352 384
WIRE 352 400 144 400
WIRE 480 400 480 384
WIRE 480 400 352 400
FLAG 0 400 0
SYMBOL voltage 0 224 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24
SYMBOL npn 416 128 R0
SYMATTR InstName Q1
SYMATTR Value 2N3055
SYMBOL res 464 288 R0
SYMATTR InstName R1
SYMATTR Value {24/.4}
SYMBOL potentiometer 128 48 R0
WINDOW 3 -72 140 Left 0
SYMATTR Value Rtot=10K wiper={X}
SYMATTR InstName U1
SYMBOL npn 288 64 R0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL diode 368 384 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value 1N914
SYMBOL res 368 288 R180
WINDOW 0 36 76 Left 0
WINDOW 3 36 40 Left 0
SYMATTR InstName R2
SYMATTR Value 1k
TEXT -32 424 Left 0 !.op
TEXT -48 472 Left 0 !.step param X .1 .9 .1
------------ end of pot-motor.asc ----------------------

Now I don't have a 2N3055 handy... But I do have an NPN - PMD16K100
Transistor laying around I could use. Would it be okay if I swapped
them? Here are the stats of the PMD16K100:

source:www.nteinc.com/specs/200to299/pdf/nte251.pdf

Absolute Maximum Ratings: (TA = +25°C unless otherwise specified)
Collector-Emitter Voltage,
VCEO . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 100Vb
Collector-Base Voltage,
VCB . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . .
100V
Emitter-Base Voltage,
VEB . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . .
5V
Collector Current, IC

Continuous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .  .. . . . . . . . . .
20A

Peak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .  . .. . . . . . . . . .
40A
Base Current,
IB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
500mA
Total Power Dissipation (TC = +25°C),
PD . . . . . . . . . . . . .. . . . . . . . . . 160W
       Derate Above
25°C . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
0.915W/°C
Operating Junction Temperature Range,
TJ . . . . . . . . . . . . . .. . . . . . . . . -65° to +200°C
Storage Temperature Range,
Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -65° to
+200°C
Thermal Resistance, Junction-to-Case,
RthJC . . . . . . . . . . . . . . . . . . . . . 1.09°C/W

And here is the stats for the 2N3055 just for reference:

Source:http://www.onsemi.com/pub/Collateral/2N3055-D.PDF

Collector-Emitter Voltage                     VCEO        60      Vdc
Collector-Emitter Voltage                     VCER        70
Vdc
Collector-Base Voltage                         VCB         100     Vdc
Emitter-Base Voltage                           VEB          7
Vdc
 Collector Current - Continuous            IC             15      Adc
Base Current                                          IB
7        Adc
Total Power Dissipation @ TC = 25°C    PD            115     W
Derate Above 25°C                                                0.657
W/°C
Operating and Storage Junction
    Temperature Range                           TJ, Tstg   -65 to
+200°C

Thanks!

You can use that. Just add a 4.7K resistor & diode
across the motor to your original:

  V+ ---+---------------+
        |               |
        P              /c
        O<---[4.7K]---|    NPN PMD16K100
        T              \e
        |               |
        +------>|-------+
        |               |
  Gnd --+---[Motor]-----+

Ed

I was planning on using a darlington pair for this project...

 

[Bob Monsen]

"kayvee" <kmvgroups@gmail.com> wrote in message
news:80a38d0c-8ab7-4dc1-8cc0-eda7cfe0d6b9@x14g2000yqk.googlegroups.com...
I was planning on using a darlington pair for this project...

Your transistor is already a darlington transistor, meaning the two
transistors is built into it, so use ehsjr's circuit, and you'll be fine.

Regards,
Bob Monsen

 

On Nov 25, 12:06 pm, "Bob Monsen" <robertmon...@sbcglobal.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message

news:80a38d0c-8ab7-4dc1-8cc0-eda7cfe0d6b9@x14g2000yqk.googlegroups.com...
I was planning on using a darlington pair for this project...

Your transistor is already a darlington transistor, meaning the two
transistors is built into it, so use ehsjr's circuit, and you'll be fine.

Regards,
 Bob Monsen

oh, perfect! Would a 10k pot still do the trick?

 

On Nov 25, 12:06 pm, "Bob Monsen" <robertmon...@sbcglobal.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message

news:80a38d0c-8ab7-4dc1-8cc0-eda7cfe0d6b9@x14g2000yqk.googlegroups.com...
I was planning on using a darlington pair for this project...

Your transistor is already a darlington transistor, meaning the two
transistors is built into it, so use ehsjr's circuit, and you'll be fine.

Regards,
 Bob Monsen

oh, perfect! Would a 10k pot still do the trick?

 

[kayvee]

On Nov 25, 12:06 pm, "Bob Monsen" <robertmon...@sbcglobal.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message

news:80a38d0c-8ab7-4dc1-8cc0-eda7cfe0d6b9@x14g2000yqk.googlegroups.com...
I was planning on using a darlington pair for this project...

Your transistor is already a darlington transistor, meaning the two
transistors is built into it, so use ehsjr's circuit, and you'll be fine.

Regards,
 Bob Monsen

oh perfect! Will my 10k pot still be fine?

 

[Paul E. Schoen]

"kayvee" <kmvgroups@gmail.com> wrote in message
news:88fbbd1b-04fd-4a85-bcac-e70207cd7960@d32g2000yqe.googlegroups.com...
On Nov 25, 12:06 pm, "Bob Monsen" <robertmon...@sbcglobal.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message

news:80a38d0c-8ab7-4dc1-8cc0-eda7cfe0d6b9@x14g2000yqk.googlegroups.com...
I was planning on using a darlington pair for this project...

Your transistor is already a darlington transistor, meaning the two
transistors is built into it, so use ehsjr's circuit, and you'll be fine.

Regards,
Bob Monsen

oh perfect! Will my 10k pot still be fine?

=======================================================

10k pot is fine, and really the 4.7 k base resistor is not necessary for an
emitter follower.

You will only be able to get about 22.5 volts from a 24 VDC supply with a
darlington.

You can get a bit more by using a
http://en.wikipedia.org/wiki/Sziklai_pair, as in the following LTspice
circuit, but you need to put the motor (simulated by a resistor and
inductor) from the positive rail to the collector of the NPN, or use a
power PNP transistor with NPN driver.

I set up a programmed voltage source and 5k resistor to simulate the pot,
and it shows the inductive kick from the motor when it is turned off
quickly. A real motor will also exhibit back EMF due to its action as a
generator as it coasts to a stop.

Paul

=======================================================

Version 4
SHEET 1 880 680
WIRE 352 -128 32 -128
WIRE 448 -128 352 -128
WIRE 448 -64 448 -128
WIRE 352 -32 352 -48
WIRE 352 64 352 48
WIRE 448 64 448 0
WIRE 448 64 352 64
WIRE 352 96 352 64
WIRE 352 96 256 96
WIRE 32 128 32 -128
WIRE 192 144 160 144
WIRE 160 176 160 144
WIRE 352 176 352 96
WIRE 256 224 256 192
WIRE 288 224 256 224
WIRE 160 288 160 256
WIRE 32 432 32 208
WIRE 160 432 160 368
WIRE 160 432 32 432
WIRE 352 432 352 272
WIRE 352 432 160 432
WIRE 32 448 32 432
FLAG 32 448 0
SYMBOL voltage 32 112 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24
SYMBOL pnp 192 192 M180
SYMATTR InstName Q1
SYMATTR Value 2N3906
SYMBOL npn 288 176 R0
SYMATTR InstName Q2
SYMATTR Value 2N3055
SYMBOL res 336 -144 R0
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL diode 464 0 R180
WINDOW 0 -25 64 Left 0
WINDOW 3 -99 0 Left 0
SYMATTR InstName D1
SYMATTR Value MURS120
SYMBOL ind 336 -48 R0
SYMATTR InstName L1
SYMATTR Value 100m
SYMBOL voltage 160 272 R0
WINDOW 3 -95 138 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value PWL(0 24 0.1 0 0.9 0 0.901 24)
SYMBOL res 144 160 R0
SYMATTR InstName R2
SYMATTR Value 5k
TEXT -2 472 Left 0 !.tran 1 startup

 

[Paul E. Schoen]

<kielvereecken@gmail.com> wrote in message
news:4939e8db-51a5-48f5-8e6a-e2d086280a42@x8g2000yqk.googlegroups.com...
On Nov 25, 5:03 pm, "Paul E. Schoen" <pst...@smart.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message

news:88fbbd1b-04fd-4a85-bcac-e70207cd7960@d32g2000yqe.googlegroups.com...
On Nov 25, 12:06 pm, "Bob Monsen" <robertmon...@sbcglobal.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message

news:80a38d0c-8ab7-4dc1-8cc0-eda7cfe0d6b9@x14g2000yqk.googlegroups.com...
I was planning on using a darlington pair for this project...

Your transistor is already a darlington transistor, meaning the two
transistors is built into it, so use ehsjr's circuit, and you'll be
fine.

Regards,
Bob Monsen

oh perfect! Will my 10k pot still be fine?

=======================================================

10k pot is fine, and really the 4.7 k base resistor is not necessary for
an
emitter follower.

You will only be able to get about 22.5 volts from a 24 VDC supply with a
darlington.

You can get a bit more by using
ahttp://en.wikipedia.org/wiki/Sziklai_pair, as in the following LTspice
circuit, but you need to put the motor (simulated by a resistor and
inductor) from the positive rail to the collector of the NPN, or use a
power PNP transistor with NPN driver.

I set up a programmed voltage source and 5k resistor to simulate the pot,
and it shows the inductive kick from the motor when it is turned off
quickly. A real motor will also exhibit back EMF due to its action as a
generator as it coasts to a stop.

Paul

=======================================================

Actually, a Sziklai pair might be the best for me, because the
PMD16K100 I snagged turns out to be a PNP transistor, rather than a
NPN, which a assumed it was.

Now would I hook it up like this?

24V------o----------------.
| |
| |/
| o------| PMD16K100 (PNP)
| | |<
| | |
.-. |/ |
10k | |<---| 2N4401 |
| | |> |
'-' | |
| | |
| '--------o
| |
| .--------o
| | |
| | .---o----.
| - | |
| ^ | motor |
| 1N4001 | |
| | '---o----'
| | |
| | |
GND--------o-------o--------'

From my research, your PMD16K100 is an NPN darlington, and its PNP
complement is PMD17K100. If it is actually a PNP, then your hook-up is
correct. Being a darlington, you lose another 1/2 volt. The data sheet I
was directed to was:
http://www.nteinc.com/specs/200to299/pdf/nte251.pdf from the site:
http://www.electronics-lab.com/downloads/datasheets/high_power_transistors.html

Make sure you determine the correct polarity for the transistor. Sometimes
an ohmmeter check can give confusing indications.

Paul

 

[Sjouke Burry]

kielvereecken@gmail.com wrote:

On Nov 25, 5:03 pm, "Paul E. Schoen" <pst...@smart.net> wrote:
"kayvee" <kmvgro...@gmail.com> wrote in message

news:88fbbd1b-04fd-4a85-bcac-e70207cd7960@d32g2000yqe.googlegroups.com...
On Nov 25, 12:06 pm, "Bob Monsen" <robertmon...@sbcglobal.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message
news:80a38d0c-8ab7-4dc1-8cc0-eda7cfe0d6b9@x14g2000yqk.googlegroups.com...
I was planning on using a darlington pair for this project...
Your transistor is already a darlington transistor, meaning the two
transistors is built into it, so use ehsjr's circuit, and you'll be fine.
Regards,
Bob Monsen
oh perfect! Will my 10k pot still be fine?

=======================================================

10k pot is fine, and really the 4.7 k base resistor is not necessary for an
emitter follower.

You will only be able to get about 22.5 volts from a 24 VDC supply with a
darlington.

You can get a bit more by using ahttp://en.wikipedia.org/wiki/Sziklai_pair, as in the following LTspice
circuit, but you need to put the motor (simulated by a resistor and
inductor) from the positive rail to the collector of the NPN, or use a
power PNP transistor with NPN driver.

I set up a programmed voltage source and 5k resistor to simulate the pot,
and it shows the inductive kick from the motor when it is turned off
quickly. A real motor will also exhibit back EMF due to its action as a
generator as it coasts to a stop.

Paul

=======================================================

Version 4
SHEET 1 880 680
WIRE 352 -128 32 -128
WIRE 448 -128 352 -128
WIRE 448 -64 448 -128
WIRE 352 -32 352 -48
WIRE 352 64 352 48
WIRE 448 64 448 0
WIRE 448 64 352 64
WIRE 352 96 352 64
WIRE 352 96 256 96
WIRE 32 128 32 -128
WIRE 192 144 160 144
WIRE 160 176 160 144
WIRE 352 176 352 96
WIRE 256 224 256 192
WIRE 288 224 256 224
WIRE 160 288 160 256
WIRE 32 432 32 208
WIRE 160 432 160 368
WIRE 160 432 32 432
WIRE 352 432 352 272
WIRE 352 432 160 432
WIRE 32 448 32 432
FLAG 32 448 0
SYMBOL voltage 32 112 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24
SYMBOL pnp 192 192 M180
SYMATTR InstName Q1
SYMATTR Value 2N3906
SYMBOL npn 288 176 R0
SYMATTR InstName Q2
SYMATTR Value 2N3055
SYMBOL res 336 -144 R0
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL diode 464 0 R180
WINDOW 0 -25 64 Left 0
WINDOW 3 -99 0 Left 0
SYMATTR InstName D1
SYMATTR Value MURS120
SYMBOL ind 336 -48 R0
SYMATTR InstName L1
SYMATTR Value 100m
SYMBOL voltage 160 272 R0
WINDOW 3 -95 138 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value PWL(0 24 0.1 0 0.9 0 0.901 24)
SYMBOL res 144 160 R0
SYMATTR InstName R2
SYMATTR Value 5k
TEXT -2 472 Left 0 !.tran 1 startup

Actually, a Sziklai pair might be the best for me, because the
PMD16K100 I snagged turns out to be a PNP transistor, rather than a
NPN, which a assumed it was.

Now would I hook it up like this?

24V------o----------------.
| |
| |/
| o------| PMD16K100 (PNP)
| | |
| | |
.-. |/ |
10k | |<---| 2N4401 |
| | |> |
'-' | |
| | |
| '--------o
| |
| .--------o
| | |
| | .---o----.
| - | |
| ^ | motor |
| 1N4001 | |
| | '---o----'
| | |
| | |
GND--------o-------o--------'

A pnp transistor with the colle3ctor to the + side? No way.
Stick to one npn darlington instead.

 

On Nov 25, 5:03 pm, "Paul E. Schoen" <pst...@smart.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message

news:88fbbd1b-04fd-4a85-bcac-e70207cd7960@d32g2000yqe.googlegroups.com...
On Nov 25, 12:06 pm, "Bob Monsen" <robertmon...@sbcglobal.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message

news:80a38d0c-8ab7-4dc1-8cc0-eda7cfe0d6b9@x14g2000yqk.googlegroups.com....
I was planning on using a darlington pair for this project...

Your transistor is already a darlington transistor, meaning the two
transistors is built into it, so use ehsjr's circuit, and you'll be fine.

Regards,
Bob Monsen

oh perfect! Will my 10k pot still be fine?

======================================================
10k pot is fine, and really the 4.7 k base resistor is not necessary for an
emitter follower.

You will only be able to get about 22.5 volts from a 24 VDC supply with a
darlington.

You can get a bit more by using ahttp://en.wikipedia.org/wiki/Sziklai_pair, as in the following LTspice
circuit, but you need to put the motor (simulated by a resistor and
inductor) from the positive rail to the collector of the NPN, or use a
power PNP transistor with NPN driver.

I set up a programmed voltage source and 5k resistor to simulate the pot,
and it shows the inductive kick from the motor when it is turned off
quickly. A real motor will also exhibit back EMF due to its action as a
generator as it coasts to a stop.

Paul

======================================================
Version 4
SHEET 1 880 680
WIRE 352 -128 32 -128
WIRE 448 -128 352 -128
WIRE 448 -64 448 -128
WIRE 352 -32 352 -48
WIRE 352 64 352 48
WIRE 448 64 448 0
WIRE 448 64 352 64
WIRE 352 96 352 64
WIRE 352 96 256 96
WIRE 32 128 32 -128
WIRE 192 144 160 144
WIRE 160 176 160 144
WIRE 352 176 352 96
WIRE 256 224 256 192
WIRE 288 224 256 224
WIRE 160 288 160 256
WIRE 32 432 32 208
WIRE 160 432 160 368
WIRE 160 432 32 432
WIRE 352 432 352 272
WIRE 352 432 160 432
WIRE 32 448 32 432
FLAG 32 448 0
SYMBOL voltage 32 112 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24
SYMBOL pnp 192 192 M180
SYMATTR InstName Q1
SYMATTR Value 2N3906
SYMBOL npn 288 176 R0
SYMATTR InstName Q2
SYMATTR Value 2N3055
SYMBOL res 336 -144 R0
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL diode 464 0 R180
WINDOW 0 -25 64 Left 0
WINDOW 3 -99 0 Left 0
SYMATTR InstName D1
SYMATTR Value MURS120
SYMBOL ind 336 -48 R0
SYMATTR InstName L1
SYMATTR Value 100m
SYMBOL voltage 160 272 R0
WINDOW 3 -95 138 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value PWL(0 24 0.1 0 0.9 0 0.901 24)
SYMBOL res 144 160 R0
SYMATTR InstName R2
SYMATTR Value 5k
TEXT -2 472 Left 0 !.tran 1 startup

Actually, a Sziklai pair might be the best for me, because the
PMD16K100 I snagged turns out to be a PNP transistor, rather than a
NPN, which a assumed it was.

Now would I hook it up like this?

24V------o----------------.
| |
| |/
| o------| PMD16K100 (PNP)
| | |<
| | |
.-. |/ |
10k | |<---| 2N4401 |
| | |> |
'-' | |
| | |
| '--------o
| |
| .--------o
| | |
| | .---o----.
| - | |
| ^ | motor |
| 1N4001 | |
| | '---o----'
| | |
| | |
GND--------o-------o--------'

 

[Jamie]

Sjouke Burry wrote:

kielvereecken@gmail.com wrote:

On Nov 25, 5:03 pm, "Paul E. Schoen" <pst...@smart.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message

news:88fbbd1b-04fd-4a85-bcac-e70207cd7960@d32g2000yqe.googlegroups.com...

On Nov 25, 12:06 pm, "Bob Monsen" <robertmon...@sbcglobal.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message
news:80a38d0c-8ab7-4dc1-8cc0-eda7cfe0d6b9@x14g2000yqk.googlegroups.com...

I was planning on using a darlington pair for this project...
Your transistor is already a darlington transistor, meaning the two
transistors is built into it, so use ehsjr's circuit, and you'll be
fine.
Regards,
Bob Monsen

oh perfect! Will my 10k pot still be fine?

=======================================================

10k pot is fine, and really the 4.7 k base resistor is not necessary
for an
emitter follower.

You will only be able to get about 22.5 volts from a 24 VDC supply
with a
darlington.

You can get a bit more by using
ahttp://en.wikipedia.org/wiki/Sziklai_pair, as in the following LTspice
circuit, but you need to put the motor (simulated by a resistor and
inductor) from the positive rail to the collector of the NPN, or use a
power PNP transistor with NPN driver.

I set up a programmed voltage source and 5k resistor to simulate the
pot,
and it shows the inductive kick from the motor when it is turned off
quickly. A real motor will also exhibit back EMF due to its action as a
generator as it coasts to a stop.

Paul

=======================================================

Version 4
SHEET 1 880 680
WIRE 352 -128 32 -128
WIRE 448 -128 352 -128
WIRE 448 -64 448 -128
WIRE 352 -32 352 -48
WIRE 352 64 352 48
WIRE 448 64 448 0
WIRE 448 64 352 64
WIRE 352 96 352 64
WIRE 352 96 256 96
WIRE 32 128 32 -128
WIRE 192 144 160 144
WIRE 160 176 160 144
WIRE 352 176 352 96
WIRE 256 224 256 192
WIRE 288 224 256 224
WIRE 160 288 160 256
WIRE 32 432 32 208
WIRE 160 432 160 368
WIRE 160 432 32 432
WIRE 352 432 352 272
WIRE 352 432 160 432
WIRE 32 448 32 432
FLAG 32 448 0
SYMBOL voltage 32 112 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24
SYMBOL pnp 192 192 M180
SYMATTR InstName Q1
SYMATTR Value 2N3906
SYMBOL npn 288 176 R0
SYMATTR InstName Q2
SYMATTR Value 2N3055
SYMBOL res 336 -144 R0
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL diode 464 0 R180
WINDOW 0 -25 64 Left 0
WINDOW 3 -99 0 Left 0
SYMATTR InstName D1
SYMATTR Value MURS120
SYMBOL ind 336 -48 R0
SYMATTR InstName L1
SYMATTR Value 100m
SYMBOL voltage 160 272 R0
WINDOW 3 -95 138 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value PWL(0 24 0.1 0 0.9 0 0.901 24)
SYMBOL res 144 160 R0
SYMATTR InstName R2
SYMATTR Value 5k
TEXT -2 472 Left 0 !.tran 1 startup


Actually, a Sziklai pair might be the best for me, because the
PMD16K100 I snagged turns out to be a PNP transistor, rather than a
NPN, which a assumed it was.

Now would I hook it up like this?

24V------o----------------.
| |
| |/
| o------| PMD16K100 (PNP)
| | |
| | |
.-. |/ |
10k | |<---| 2N4401 |
| | |> |
'-' | |
| | |
| '--------o
| |
| .--------o
| | |
| | .---o----.
| - | |
| ^ | motor |
| 1N4001 | |
| | '---o----'
| | |
| | |
GND--------o-------o--------'


A pnp transistor with the colle3ctor to the + side? No way.
Stick to one npn darlington instead.
Actually, you can use the PNP, it's just upside down.

the emitter needs to go to the (+).

This configuration works well with in a 0.7 V window of
regulation.

http://webpages.charter.net/jamie_5"

 

[kayvee]

On Nov 25, 6:59 pm, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:

Sjouke Burry wrote:
kielvereec...@gmail.com wrote:

On Nov 25, 5:03 pm, "Paul E. Schoen" <pst...@smart.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message

news:88fbbd1b-04fd-4a85-bcac-e70207cd7960@d32g2000yqe.googlegroups.com....

On Nov 25, 12:06 pm, "Bob Monsen" <robertmon...@sbcglobal.net> wrote:

"kayvee" <kmvgro...@gmail.com> wrote in message
news:80a38d0c-8ab7-4dc1-8cc0-eda7cfe0d6b9@x14g2000yqk.googlegroups.com...

I was planning on using a darlington pair for this project...
Your transistor is already a darlington transistor, meaning the two
transistors is built into it, so use ehsjr's circuit, and you'll be
fine.
Regards,
Bob Monsen

oh perfect! Will my 10k pot still be fine?

======================================================
10k pot is fine, and really the 4.7 k base resistor is not necessary
for an
emitter follower.

You will only be able to get about 22.5 volts from a 24 VDC supply
with a
darlington.

You can get a bit more by using
ahttp://en.wikipedia.org/wiki/Sziklai_pair, as in the following LTspice
circuit, but you need to put the motor (simulated by a resistor and
inductor) from the positive rail to the collector of the NPN, or use a
power PNP transistor with NPN driver.

I set up a programmed voltage source and 5k resistor to simulate the
pot,
and it shows the inductive kick from the motor when it is turned off
quickly. A real motor will also exhibit back EMF due to its action as a
generator as it coasts to a stop.

Paul

======================================================
Version 4
SHEET 1 880 680
WIRE 352 -128 32 -128
WIRE 448 -128 352 -128
WIRE 448 -64 448 -128
WIRE 352 -32 352 -48
WIRE 352 64 352 48
WIRE 448 64 448 0
WIRE 448 64 352 64
WIRE 352 96 352 64
WIRE 352 96 256 96
WIRE 32 128 32 -128
WIRE 192 144 160 144
WIRE 160 176 160 144
WIRE 352 176 352 96
WIRE 256 224 256 192
WIRE 288 224 256 224
WIRE 160 288 160 256
WIRE 32 432 32 208
WIRE 160 432 160 368
WIRE 160 432 32 432
WIRE 352 432 352 272
WIRE 352 432 160 432
WIRE 32 448 32 432
FLAG 32 448 0
SYMBOL voltage 32 112 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24
SYMBOL pnp 192 192 M180
SYMATTR InstName Q1
SYMATTR Value 2N3906
SYMBOL npn 288 176 R0
SYMATTR InstName Q2
SYMATTR Value 2N3055
SYMBOL res 336 -144 R0
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL diode 464 0 R180
WINDOW 0 -25 64 Left 0
WINDOW 3 -99 0 Left 0
SYMATTR InstName D1
SYMATTR Value MURS120
SYMBOL ind 336 -48 R0
SYMATTR InstName L1
SYMATTR Value 100m
SYMBOL voltage 160 272 R0
WINDOW 3 -95 138 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value PWL(0 24 0.1 0 0.9 0 0.901 24)
SYMBOL res 144 160 R0
SYMATTR InstName R2
SYMATTR Value 5k
TEXT -2 472 Left 0 !.tran 1 startup

Actually, a Sziklai pair might be the best for me, because the
PMD16K100 I snagged turns out to be a PNP transistor, rather than a
NPN, which a assumed it was.

Now would I hook it up like this?

  24V------o----------------.
           |                |
           |              |/
           |       o------|  PMD16K100 (PNP)
           |       |      |
           |       |        |
          .-.    |/         |
     10k  | |<---|  2N4401  |
          | |    |>         |
          '-'      |        |
           |       |        |
           |       '--------o
           |                |
           |       .--------o
           |       |        |
           |       |    .---o----.
           |       -    |        |
           |       ^    | motor  |
           |  1N4001    |        |
           |       |    '---o----'
           |       |        |
           |       |        |
GND--------o-------o--------'

A pnp transistor with the colle3ctor to the + side? No way.
Stick to one npn darlington instead.

Actually, you can use the PNP, it's just upside down.
  the emitter needs to go to the (+).

    This configuration works well with in a 0.7 V window of
regulation.

http://webpages.charter.net/jamie_5"

So Jamie, this looks better:

24V------o----------------.
| |
| |<
| o------| PMD16K100 (PNP)
| | |\
| | |
.-. |/ |
10k | |<---| 2N4401 |
| | |> |
'-' | |
| | |
| '--------o
| |
| .--------o
| | |
| | .---o----.
| - | |
| ^ | motor |
| 1N4001 | |
| | '---o----'
| | |
| | |
GND--------o-------o--------'