What is a rheostat type pedal?

What is a rheostat type pedal?
What is a rheostat type pedal?

What is a rheostat type pedal? This is an electric foot pedal for sewing machines. It has nothing inside, except for one detail - a pedal rheostat. It acts as an on/off switch for the sewing machine motor. It differs from a simple switch in that it smoothly, gradually turns the engine on and off.

sewing pedal

Operation principle

Depending on the force with which the foot is pressed on the pedal, the voltage that is supplied to the electric drive of the machine changes, therefore, its rotation frequency changes and, of course, the sewing speed changes. What is a pedal? It is worth finding out how the foot pedal rheostat for a sewing machine works.

Pedal device for sewing machine

The design of the pedal rheostat, which regulates the speed of the sewing machine, is incredibly simple: graphite plates (thinly sawn) are inside the rheostat, stacked one to the other.

The principle of operation is as follows: when the graphite plates of the rheostat are inin a free state, their resistance to electric current is infinitely great. When the graphite plates are stacked next to each other, the current cannot pass through them and is not supplied to the machine's electric drive, which, in turn, does not rotate.

It is worth a little squeeze between the graphite plates, the electrical resistance between them will begin to decrease. The more they are compressed, the more electric current will be supplied through the pedal rheostat to the electric drive of the machine, and the motor will rotate faster. Accordingly, the speed of the sewing process on the sewing machine will increase.

Pedal as the cause of electric drive failure

rheostat pedal

A common cause of electric drive failure is the pedal of a sewing machine. The machine suddenly starts to stop and only after repeated pressing the pedal to the stop, it starts to work. It also happens that it stops altogether, and no matter how 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 tritely simple - the contacts of the connecting plugs have oxidized, or the wire has broken 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. Or you can just completely replace the wiring and not look for the place of the break. But only an electrician can do this, and then not inin all cases, since often the connecting plugs are not disassembled. In this case, the only way out is to buy a new pedal.

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