A motor speed controller suitable for appliances rated up to 10A. Suits brush-type universal motors such as those in small lathes, electric drills, grass trimmers, circular saws, routers, nibblers and jigsaws.
Kit includes diecast case with label & mains connection leads.
What motors can be controlled?
Virtually all mains operated power tools and small appliances use “universal” motors. These are “series wound” motors with a commutator and brushes. The “series wound” term refers to the fact that the motor armature and field windings are connected in series and this allows the motor to be run from AC or DC, hence the term “universal”.
Induction motors must not be used with this speed controller. So how do you make sure that your appliance is a universal motor and not an induction motor?
In many power tools you can easily determine that the motor has brushes and a commutator – you can see sparks from the brushes and that settles the matter. But if you can’t see the brushes, you can also get a clue from the nameplate or the instruction booklet.
So how do you identify an induction motor? Most induction motors used in domestic appliances (eg, washing machines, fridges, water blasters, swimming pool pumps) will be 2-pole or 4-pole and always operate at a fixed speed. Typically this is 2850 RPM for a 2-pole unit or 1440 RPM for a 4-pole unit. Bench grinders typically use 2-pole induction motors.
Kit originally described in the February 2009 issue of Silicon Chip magazine.