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Once you know how the motor works we can discuss the foot/knee control. Without the foot/knee 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......and.......where does the energy go? A properly designed POT will dissipate this energy safely as HEAT.
NOTE: A HOT foot/knee controller at slow speeds is working properly. A HOT foot/knee controller at full/high speeds is NOT working properly and should be looked at.
PERCEPTIONS: Some foot/knee 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 Ė 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 donít notice the heat and therefore believe it is running cooler. Newer controllers also have air vents to cool the unit even faster.
There you have it!!.....now you are up to speed on controllers! (Pun intended :-)
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