[sdiy] Tonewheel questions

[The Peasant]

Quoting Robotboy8 at aol.com:

> I'm thinking of building a vastly simplified tonewheel organ.  What I'm 
> looking at doing is a fan motor running off of wall-current with a dimmer
> (the kind 
> used on house lights) to vary the speed of the motor (overall pitch), this 
> motor being connected to a shaft with 5 (or howeverman) wheels.  My questions
> 
> are as follows:
> 1) Will the fan assembly work?  I know some fans don't 'like' lower currents
> 
> than they're used to seeing, what sort are these?

Most ac fan motors are synchronous and will want to run at a speed based on the 
ac line frequency (50/60Hz). Lowering the voltage will make them unstable but 
will not control the frequency, and may cause stalling and overheating. To use 
these motors and have speed control you would have to build a variable 
frequency ac power supply. It's easier to use dc motors and a regulated dc 
power supply.

> 2) Anything I should know about these dimmers beforehand?

They are usually bad generators of RF noise due to their phase chopping 
behaviour. I'd avoid them around any audio or music gear.

Take care,
Doug
______________________
The Electronic Peasant

www.electronicpeasant.com