What is a rheostat type pedal? This is an electric foot pedal for sewing machines. It inside has nothing but one detail - a pedal rheostat. It serves as a switch and a switch on the electric motor of the sewing machine. It differs from a simple switch in that it smoothly, gradually turns the engine on and off.
Operating principle
Depending on the force with which the foot is pressed on the pedal, the voltage that is applied to the electric drive of the machine changes, therefore, its rotation frequency changes and, of course, the sewing speed changes. What is a pedal is understandable. It is worth finding out how the rheostat of the foot pedal for the sewing machine is arranged.
Sewing machine pedal device
The design of the pedal rheostat, which controls the speed of the sewing machine, is incredibly simple: graphite plates (finely sawn) are inside the rheostat, stacked one on top of the other.
The principle of operation is as follows: when the rheostat graphite plates are in a free state, the resistance to electric current is infinitely large in them. When graphite plates are stacked one to the other, current cannot pass through them and is not supplied to the machine’s electric drive; it, in turn, does not rotate.
As soon as graphite plates are squeezed together, the electrical resistance between them begins to decrease. The stronger they are compressed, the more electric current will be supplied through the rheostat of the pedal to the electric drive of the machine, the more the motor will rotate faster. Accordingly, the speed of the sewing process on a sewing machine will increase.
Pedal as a cause of damage to the drive
A common cause of damage to the drive is the pedal of the sewing machine. The machine suddenly starts to stop and only after repeatedly pressing it all the way to the pedal does it start to work. It also happens that she stops at all, and even if you press the pedal, it will not work. The first thought that may come to mind in this situation is that the engine burned out. But in the end it turns out that the pedal just broke.
Most often, the reason for such a breakdown is corny simple - the contacts of the connecting plugs are oxidized, or the wire breaks inside the cord insulation. It is easy to eliminate the oxidation of the contacts, they just need to be cleaned with sandpaper. Now, if a wire break occurs inside the wiring, it will be very difficult to find it. You will need to use a tester. And you can just completely replace the wiring and not look for a cliff. But only an electrician can do this, and even then not in all cases, since often the connecting plugs are not understood. In this case, the only way out is to buy a new pedal.