On 7 May 2008 03:43:57 GMT, "DoN. Nichols"
wrote:



The motors on the Singer sewing machines (e.g. my 221
"Featherweight") are brush equipped universal motors, and will vary
speed with applied current and with load to some extent. These motors
will work with either DC or AC.

The foot speed controls are variable series resistance -- done
by a stack of carbon blocks which get squshed together by the foot
pressure to reduce their resistance and allow more current through to
the motor.


You might find this of interest, DoN:
http://users.goldengate.net/~dforeman/footpedal/