Inexpensive Variable Speed Control Using a Light Dimmer Switch

Tool Concept
Functional Prototype


This tool uses a modern light dimming switch to provide variable speed control of a motor (fan, pump, etc.) It turns out these dimmers use silicon controlled rectifiers (SCR's) which allow for very nice voltage control, and hence speed control in motors common to farm applications. More on SCR here:
Documentation Wiki: 

Bill of materials

A good light dimmer switch from Lutron or similar.  $20-60.

Other tools needed to build this tool

Basic wiring tools (stripper, screwdriver, etc.)

Step-by-step build instructions

Dimmer installation instructions from Lutron:

Take care to check the current rating on the switch compared to the load.  The Lutron selection tool will help you select by load (Wattage):

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