Abstract: A speed control device is provided such that the speed of DC motors is controlled to remain constant with varying voltages supplied from a power source. A given application for such a speed control device is in the use of portable, hand-held Metal Inert Gas (MIG) welders. The power requirements of a portable MIG welder are twofold. Power is required for the generation of a welding current to enable the workpieces to be sufficiently heated and thus, welded together, and power is also required to drive a wire spooler which provides wire at a constant rate, leading to accurate and consistent welds. The speed control device provided ensures constant power delivery for both power requirements, regardless of variations in the voltage of a power supply and irrespective of a mechanical load asserted on the welder.