[TheForge] Dimmer switch as motor controller

[Graham Whaley]

Hi Rich.

 Although it is not recommended, I ran an old 'universal motor' vacuum
cleaner (probably 1KVA or similar!) off of a dimmer switch for a few months,
expecting the back-emf from the motor to blow the dimmer - and never had a
problem. I picked up the cheapest dimmer I could from Wilkinsons on the
grounds that it was likely to blow.
 I believe you've got to watch out when running them at low speed on the
dimmer. The motor gets pretty unhappy (or mine did), and it may not get
enough airflow to cool it down either. I always had to start the motor up
fast and then crank the speed down. It would not start up on slow.

 Which motor/fan have you got - did you go with one of those inline
extractor fans from Screwfix in the end?

 The best suggestion I've heard in a while is to rip the passenger airflow
fan out of an old car and run it off a car battery through the speed
controller out of the car. One smith I met said that is what he used for
portable demonstrations, and it would get him 4 speeds (including off), and
run all day on one battery.

 In theory my workshop (aka. back of a large garage) should be going up on
Monday, so I might actually get the leg vice and anvil set up over xmas and
be able to beat some metal in the new year - for the first time in two
years!

 Graham

On Wed, Nov 25, 2009 at 4:43 PM, Rich Maynard <rich at maynard.org.uk> wrote:

> www.screwfix.com dimmer part number 47327 says it does resistive/inductive
> loads up to 250VA. Is a little forge fan motor an inductive load? It says
> 48W on the label.
>
> Rich M.
>
> Rich Maynard - Artist Blacksmith
> rich at muchhadhamforge.co.uk
> The Forge Experience - www.muchhadhamforge.co.uk/experience.html
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