Connected in this manner, an LM317 1-A adjustable-voltage regulator can be used to control the speed of a miniature dc motor or vary the brilliance of a small lamp. The circuit does so by controlling the pulse width, and therefore the current, to the load device. To set the desired maximum output voltage, momentarily close SI and adjust R3. Connect either a lamp or small dc motor (as is shown in the schematic to the circuit`s output) and adjust R4 for the desired results.
Any device that is driven by this circuit should have a current requirement of 1 A or less. And you should be sure to use good-sized heatsink for the LM317 regulator IC.