Speed control for motor salvaged from vintage electrical sewing machine

A vintage Singer electric sewing machine motor (240V, 50Hz, 60W) with a brushed AC design produces excessive speed for use as a drill power source. A simple, cost-effective speed control solution is sought, preferably with a hand-operated knob rather than a foot pedal. A standard electric light dimmer switch can be used to control speed on brushed AC motors, as it functions via pulse width modulation, but may offer limited speed regulation under varying loads. An alternative is a specialized speed regulator circuit using a silicon controlled rectifier (SCR), specifically a TIC106D SCR, which applies pulsed DC to the motor and provides better speed stability through back EMF feedback. This circuit, originally published in Elektor magazine (July/August 1983 issue) and available on Electroschematics.com, requires careful assembly and mains safety precautions. Other options include using a rotary wire-wound variable resistor similar to the original foot pedal resistor or powering the motor with a low-voltage DC supply (e.g., 12V DC) to achieve slower speeds. Variable transformers can also control speed but are heavy and costly. Components like inductors and capacitors for interference suppression may be salvaged from old power supplies. The discussed solutions emphasize safety due to mains voltage involvement and the need for proper insulation, especially around the SCR's metal tag (anode).
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