Questions about changing the speed of a toy motor. - echople

[bdm]

This one should be easy for most of you. My question is, what type
(rating, voltage, amp) of variable resistor or other component should
I use to connect to an old toy motor (see pic) that would allow me to
manually change it's speed? My first attempt was to connect a dimmer
switch (from a light fixture) between one of the leeds and the power
source (a.c. plug from outlet). Even with the dimmer rotated to it's
max position the motor did not spin. The specs on the label of the
motor read as follows: V.115 Hz.60 A. .25 RPM 1550

Thanks in advance, Bill.

 

[default]

On Wed, 03 Dec 2003 04:38:42 GMT, bdm <badsd@optonline.net> wrote:

This one should be easy for most of you. My question is, what type
(rating, voltage, amp) of variable resistor or other component should
I use to connect to an old toy motor (see pic) that would allow me to
manually change it's speed? My first attempt was to connect a dimmer
switch (from a light fixture) between one of the leeds and the power
source (a.c. plug from outlet). Even with the dimmer rotated to it's
max position the motor did not spin. The specs on the label of the
motor read as follows: V.115 Hz.60 A. .25 RPM 1550

Thanks in advance, Bill.
That is a shaded pole fan/blower AC motor from the looks of it.

Generally they are not suitable for speed control. The dimmer trick
will sometimes work with very small and lightly loaded motors of that
type. The dimmers themselves have trouble handling inductive loads,
so a better dimmer may work (under light load).

A variable frequency drive would control it over some range (if it
doesn't use a capacitor) but that isn't exactly cheap or easy.

Best advice would be to go back to your application and find a more
suitable motor or use some mechanical power transmission scheme to
change the speed.

There's lots of inexpensive DC motors around.


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[default]

On Wed, 03 Dec 2003 04:38:42 GMT, bdm <badsd@optonline.net> wrote:

This one should be easy for most of you. My question is, what type
(rating, voltage, amp) of variable resistor or other component should
I use to connect to an old toy motor (see pic) that would allow me to
manually change it's speed? My first attempt was to connect a dimmer
switch (from a light fixture) between one of the leeds and the power
source (a.c. plug from outlet). Even with the dimmer rotated to it's
max position the motor did not spin. The specs on the label of the
motor read as follows: V.115 Hz.60 A. .25 RPM 1550

Thanks in advance, Bill.
I just had an idea if you like to tinker . . .

I ran into a similar problem using a triac control to work a heater.
Normally this is a slam dunk - no extra arm wavin or hed skratchen.
The damn thing wouldn't control the heater reliably (triac firing was
erratic).

Analyzing the problem, I found the heater was wound in a long glass
tube (similar to an aquarium heater - but for large heavy duty
chemical use). I calculated the rough inductance based on number of
turns and spacing, and put a capacitor across the heater to cancel the
inductance. Worked like a champ.

My bet would be a similar trick would work with your AC motor. You
may not find 0-100% control and it may be sensitive to the amount of
motor loading.

You probably don't have the means to find the inductance of the motor
but some tinkering may yield a capacitor value that would work. Non
polar caps Mylar, polyester, or Polypropylene dielectric for low
dissipation. Rated around three times the AC voltage if they are DC
caps. It would probably fall into the 1-10 micro farad range.

Anyone on the group tried anything like that? Did it work?


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[Jerry G.]

The standard AC type motors are frequency dependent for their speed, not
voltage dependent. A dimmer, infact may damage the motor, rather than change
its speed, for many complex reasons.

You should find the proper motor for your application. There are motors that
are designed to work with speed control.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"bdm" <badsd@optonline.net> wrote in message
news:k4qqsv48ah16df8t5tu4j26f4p3pkb8sf4@4ax.com...
This one should be easy for most of you. My question is, what type
(rating, voltage, amp) of variable resistor or other component should
I use to connect to an old toy motor (see pic) that would allow me to
manually change it's speed? My first attempt was to connect a dimmer
switch (from a light fixture) between one of the leeds and the power
source (a.c. plug from outlet). Even with the dimmer rotated to it's
max position the motor did not spin. The specs on the label of the
motor read as follows: V.115 Hz.60 A. .25 RPM 1550

Thanks in advance, Bill.

 

[N. Thornton]

"bdm" <badsd@optonline.net> wrote in message
news:k4qqsv48ah16df8t5tu4j26f4p3pkb8sf4@4ax.com...
This one should be easy for most of you. My question is, what type
(rating, voltage, amp) of variable resistor or other component should
I use to connect to an old toy motor (see pic) that would allow me to
manually change it's speed? My first attempt was to connect a dimmer
switch (from a light fixture) between one of the leeds and the power
source (a.c. plug from outlet). Even with the dimmer rotated to it's
max position the motor did not spin. The specs on the label of the
motor read as follows: V.115 Hz.60 A. .25 RPM 1550

Thanks in advance, Bill.

Hi

If this is a shaded pole motor, presumably one could use a circuit
that passes only every third half cycle to the motor. Anyone tried
this?

Regards, NT

PS this newsgroup doesnt carry pics.

 

[Electrode]

Bill,

There are two recommendations, and one warning:

AC Motors usually work on induction. This means to generate torque, a
current flows through the coil, and generates another current in the
rotor. This is similar to a transformer. If the load on the motor
decreases with speed, such as a fan, you can usually vary the voltage
to change the speed.

Warning: AC motors will try to establish, through transformer
operation, enough magnetic energy to rotate. Very basically, at lower
voltages, the motor current will rise - given the same load. Hence
the requirement to have the load reduce with motor speed (voltage),
and a limitation on how much you can reduce the voltage.

Now on to your other problem - inductive loads take a while for
current to flow after the voltage rises in the AC cycle. This means
that voltage and current are out of phase. The triac in the dimmer
expects load current shortly after the the gate is triggered, and for
that current to remain throughout the cycle.

So, add a small incadescent lamp across the motor loads. Its
resistive characteristics will serve to keep the triac energized, and
the dimmer will work. A small, 15W bulb will be fine. SOme dimmers
will work with a 7.5W bulb.

WATCH THE MOTOR TEMPERATURE. If you go too low in voltage (about 85
RMS), the input current will rise dramatically, the motor will stall,
and the motor will get smoking hot.


news:<a7076635.0312040526.4f794914@posting.google.com>...

"bdm" <badsd@optonline.net> wrote in message
news:k4qqsv48ah16df8t5tu4j26f4p3pkb8sf4@4ax.com...
This one should be easy for most of you. My question is, what type
(rating, voltage, amp) of variable resistor or other component should
I use to connect to an old toy motor (see pic) that would allow me to
manually change it's speed? My first attempt was to connect a dimmer
switch (from a light fixture) between one of the leeds and the power
source (a.c. plug from outlet). Even with the dimmer rotated to it's
max position the motor did not spin. The specs on the label of the
motor read as follows: V.115 Hz.60 A. .25 RPM 1550

Thanks in advance, Bill.


Hi

If this is a shaded pole motor, presumably one could use a circuit
that passes only every third half cycle to the motor. Anyone tried
this?

Regards, NT

PS this newsgroup doesnt carry pics.