control dc motor speed

M

monkeys paw

Guest
I have a simple multi voltage transformer and a dc motor. When hooking
the power supply to the motor to spin a light platform, the motor
spins too fast. What type of circuit would allow me to control
the motor speed. I tried putting a resistor in the path and got
not motion from the motor at all ( i tried multiple resistor sizes)


I also tried this unsuccessfully:


6v+
|
|
r1 = 2.2k
|
|------------- motor ---|ground
|
r2 = 2.2k
|
-
ground

Please help or refer me to an internet page, thank you
 
monkeys paw wrote:
I have a simple multi voltage transformer and a dc motor. When hooking
the power supply to the motor to spin a light platform, the motor
spins too fast. What type of circuit would allow me to control
the motor speed. I tried putting a resistor in the path and got
not motion from the motor at all ( i tried multiple resistor sizes)


I also tried this unsuccessfully:


6v+
|
|
r1 = 2.2k
|
|------------- motor ---|ground
|
r2 = 2.2k
|
-
ground

Please help or refer me to an internet page, thank you
Click to expand...

How about using PWM speed control which would be more efficient than
using resistors?
For example:
http://www.electronics-lab.com/projects/motor_light/038/
 
"GM" <nospam@please.com> wrote in message
news:foebs6$jt5$1@volcano1.grnet.gr...
monkeys paw wrote:
I have a simple multi voltage transformer and a dc motor. When hooking
the power supply to the motor to spin a light platform, the motor
spins too fast. What type of circuit would allow me to control
the motor speed. I tried putting a resistor in the path and got
not motion from the motor at all ( i tried multiple resistor sizes)


I also tried this unsuccessfully:


6v+
|
|
r1 = 2.2k
|
|------------- motor ---|ground
|
r2 = 2.2k
|
-
ground

Please help or refer me to an internet page, thank you


How about using PWM speed control which would be more efficient than
using resistors?
For example:
http://www.electronics-lab.com/projects/motor_light/038/
Click to expand...


I think he wants something cheap and workable. I use resistor as well to
decrease the Fuel Pump of my Mercedes, it works fine as you as you know how
much the motor draw the current. Then you can always figure out that you
want to draw 10-15% of the total current draw. There is a simple math for
this. V/I = R.

Hey my dear Money, what you have to do is to measure the current draw on
your motor at full speed first. Got an Amp meter? put it in series, start
measuring from 10A downward. Once you got your current reading, the rest
is a piece of cake. The current is the I. The V=Voltage, you already
know.

Now the math would be like this (V/I)*.20 = The value of a Resistor you
need to put in to slow the motor down by 20%. Use 5 to 10 watts resistor
for small motor. For bigger motor you need 20W or higher.

Jack.
 
"monkeys paw" <user@example.net> wrote in message
news:ZtqdnSwHIJp8MTfanZ2dnUVZ_hOdnZ2d@insightbb.com...
I have a simple multi voltage transformer and a dc motor. When hooking
the power supply to the motor to spin a light platform, the motor
spins too fast. What type of circuit would allow me to control
the motor speed. I tried putting a resistor in the path and got
not motion from the motor at all ( i tried multiple resistor sizes)


I also tried this unsuccessfully:


6v+
|
|
r1 = 2.2k
|
|------------- motor ---|ground
|
r2 = 2.2k
|
-
ground

Please help or refer me to an internet page, thank you
Click to expand...



"GM" <nospam@please.com> wrote in message
news:foebs6$jt5$1@volcano1.grnet.gr...
monkeys paw wrote:
I have a simple multi voltage transformer and a dc motor. When hooking
the power supply to the motor to spin a light platform, the motor
spins too fast. What type of circuit would allow me to control
the motor speed. I tried putting a resistor in the path and got
not motion from the motor at all ( i tried multiple resistor sizes)


I also tried this unsuccessfully:


6v+
|
|
r1 = 2.2k
|
|------------- motor ---|ground
|
r2 = 2.2k
|
-
ground

Please help or refer me to an internet page, thank you


How about using PWM speed control which would be more efficient than
using resistors?
For example:
http://www.electronics-lab.com/projects/motor_light/038/
Click to expand...


I think you want something cheap and workable. I use a resistor as well to
decrease the Fuel Pump of my Mercedes, it works fine as long as you know
how
much the motor draws the current. Then you can always figure out that you
want to draw 10-15% of the total current draw. There is a simple math for
this. V/I = R.

Hey my dear Money, what you have to do is to measure the current draw on
your motor at full speed first. Got an Amp meter? put it in series, start
measuring from 10A downward. Once you got your current reading, the rest
is a piece of cake. The current is the I. The V=Voltage, you already
know.

Now the math would be like this (V/I)*.20 = The value of a Resistor you
need to put in to slow the motor down by 20%. Use 5 to 10 watts resistor
for small motor. For bigger motor you need 20W or higher.

Jack.

- PS. Don't add a resistor on your car, because you don't have the fuel
efficiency booster otherwise you car will not start.
 
"Jakthehammer" <jakthhmmr@aol.com> wrote in message
news:foeo7c$1lr$1@aioe.org...
"monkeys paw" <user@example.net> wrote in message
news:ZtqdnSwHIJp8MTfanZ2dnUVZ_hOdnZ2d@insightbb.com...
I have a simple multi voltage transformer and a dc motor. When hooking
the power supply to the motor to spin a light platform, the motor
spins too fast. What type of circuit would allow me to control
the motor speed. I tried putting a resistor in the path and got
not motion from the motor at all ( i tried multiple resistor sizes)


I also tried this unsuccessfully:


6v+
|
|
r1 = 2.2k
|
|------------- motor ---|ground
|
r2 = 2.2k
|
-
ground

Please help or refer me to an internet page, thank you




"GM" <nospam@please.com> wrote in message
news:foebs6$jt5$1@volcano1.grnet.gr...
monkeys paw wrote:
I have a simple multi voltage transformer and a dc motor. When hooking
the power supply to the motor to spin a light platform, the motor
spins too fast. What type of circuit would allow me to control
the motor speed. I tried putting a resistor in the path and got
not motion from the motor at all ( i tried multiple resistor sizes)


I also tried this unsuccessfully:


6v+
|
|
r1 = 2.2k
|
|------------- motor ---|ground
|
r2 = 2.2k
|
-
ground

Please help or refer me to an internet page, thank you


How about using PWM speed control which would be more efficient than
using resistors?
For example:
http://www.electronics-lab.com/projects/motor_light/038/



I think you want something cheap and workable. I use a resistor as well
to
decrease the Fuel Pump of my Mercedes, it works fine as long as you know
how
much the motor draws the current. Then you can always figure out that
you
want to draw 10-15% of the total current draw. There is a simple math
for
this. V/I = R.

Hey my dear Money, what you have to do is to measure the current draw on
your motor at full speed first. Got an Amp meter? put it in series,
start
measuring from 10A downward. Once you got your current reading, the rest
is a piece of cake. The current is the I. The V=Voltage, you already
know.

Now the math would be like this (V/I)*.20 = The value of a Resistor you
need to put in to slow the motor down by 20%. Use 5 to 10 watts resistor
for small motor. For bigger motor you need 20W or higher.

Jack.

- PS. Don't add a resistor on your car, because you don't have the fuel
efficiency booster otherwise you car will not start.
Click to expand...


Your schematic is far from success, even if you put 2.2K in series, your
motor will not move. You cannot do thing blindly with electronics. Your
motor probably draws about 1 -2 amps. It's about 3-ohms in motor
inductance, try putting 1 ohm, you will see it moves slower by 30%. ... I
am sleeping now... got to go.

Good luck
 
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