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Sewing machine
motors & foot controllers explained
I have had many inquiries about sewing
machine motors and foot controllers from my customers. Below are some
commonly asked questions and their answers about these topics. In case you
are wondering about the reliability of my answers; I teach Chemistry &
Physics and collect/restore sewing machines in my spare time (I lost count
after 50). I will keep my answers as simple as possible for the average
person so some explanations have been oversimplified and may not sound
correct for you engineering pros out there.
(A) 110V vs 220V Motors
Motors are basically a bunch of tiny
magnets that are lined up and designed to sometimes repel and sometimes
attract. By alternating the repelling/attracting we can force the motor to
rotate. The rotation speed is controlled by the electrical voltage (energy).
More voltage means more speed. Since sewing machines have a predetermined
TOP speed the motor is designed to achieve this TOP speed based on the
locally supplied voltage of that country.
CAUTION/REMINDER: You can use a 220V motor on a 110V source and
the TOP speed will be HALF of what it should be and there will be NO damage
to the motor. BUT…..if you use a 110V motor on a 220V source it will run at
TWICE the TOP speed and permanently damage the motor (it may even catch
fire).
(B) Converting a 220V
Motor to run on 110V
You do NOT necessarily have to buy a new
motor unless you want to. To maintain the originality of your machine and
have it running properly you should use a transformer. These can be obtained
at any electrical supply store.
First thing is to look at the
information plate on the motor of your machine. On it should be 2 vital
pieces of information: 1. the voltage of 220V and, 2. the current rating of
your machine in either Amperes (A) or milliamperes (mA). If your machine has
the info in mA (milliamperes) you will have to convert it to A (Amperes) by
dividing by 1000.
Next we need to know the Power
consumption of your machine (in Watts) which is accomplished by using the
formula P = V X I where V=volts and I=current in Amps. Lets say your machine
has the following info on the motor plate: 220volts and current of 330mA.
Change the mA to A by dividing by 1000. Now the current is 0.33A instead of
330mA. The Power will be 220 X .33 = 72.6 Watts (W).
Now you will need to buy an AC STEP-UP
transformer. This steps up the voltage from 110V to 220V and still keeps it
as AC voltage. Make sure that the OUTPUT Power rating of the transformer is
GREATER than the power you calculated for your machine by approx. 25%. In my
example, I would buy a 100 Watt Output, AC Step-up Transformer. The reason
for the extra wattage is that there will be some heat loss when the
transformer is working and you don’t want to run the transformer at its
limit. The transformer will get warm as you are using your machine so don’t
be alarmed.
You may be able to buy such a unit
already made for you with a plug socket already there so all you have to do
is plug your machine in and sew away! If that’s not the case the wiring is
very easy. If you are not electrically savvy get the supply house to show
you which 2 wires are the Primary (input) and which are the Secondary
(output). These actually should be labeled on the transformer but some of
the cheap ones aren’t. Now go to a hardware store buy some #14 electrical
wire, wall plug (2-prong), and a box to hold the transformer. Use the
Primary wires for your 110V and the Secondary wires for your 220V (machine
side) and you are ready to sew.
(C) Converting 110V
Motor to run on 220V
The information for converting 110V
motors to run on 220V is exactly the same as the info above with the
following changes: You need to buy an AC STEP-DOWN transformer and the
Primary wires must go to the 220V and the Secondary wires to the machine
side (110V).
(D) Foot Controllers
Now that you know how the motor works we
can discuss the foot control. Without the foot control your machine would
have only ONE speed and that would be its predetermined TOP speed which is
dependent upon the voltage. To allow you to vary the speed we must vary the
voltage. The ideal way to do this is to use a transformer (or variac) which
is both heavy and expensive. The simple way is to use a potentiometer
(variable resistor) which is light and cheap. The potentiometer (POT for
short) is a tightly coiled resistive wire (or Carbon stack) with a slider on
top. The slider changes the resistance which changes the voltage (energy)
that is ABSORBED by the POT. When your machine runs full out the POT absorbs
NO energy as it is all transferred to the motor. At slow speeds the POT
absorbs most of the energy and that is why it gets HOT…..where does the
energy go? A properly designed POT will dissipate this energy safely as
HEAT.
NOTE:
A HOT foot controller at slow speeds is working properly. A HOT foot
controller at full/high speeds is NOT working properly and should be looked
at.
PERCEPTIONS:
Some foot controllers are hot and others are not.
The Singer button controller seems to
run hotter than the accelerator pedal type controllers. This in fact is not
really true. The button controller is basically a sealed plastic/bakelite
model. Plastic/bakelite is an insulator which holds the heat. Since your
foot sits on the controller you are detecting the heat. The accelerator foot
pedals have 2 parts – the pedal part that your foot rests on and the base
which is usually metal which dissipates heat very well. Since your foot does
not sit on the base you don’t notice the heat and therefore believe it is
running cooler. Newer controllers also have air vents to cool the unit even
faster. |
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