I actually had one of those. Got it from a very old treadmill. Never found a use for it. Scrapped it for its copper.

Too bad; those were one of the few TM's that had a universal motor and had a speed sensor control designed specifically for it by Motorola, TDA1085.
As universal motors are normally hard to speed-control accurately, I put one of the TDA boards and motor on my bandsawfor variable speed.

 

Held onto it for about 5 years or more. After never finding a practical use for it - I decided to stop giving spiders a place to live.

We're officially off topic.

 

Given that the application is an air blower, it is not likely that precise speed control is needed. An interesting scheme could be to use PWM (on off drive power) control to vary the speed. Certainly the cycle rate will need to avoid driving any resonant portions of the assembly. Drive duty cycle control, ON/OFF should be fairly simple to do, either with s triac or a fast SSR.

 

the cycle rate will need to avoid driving any resonant portions of the assembly

Tried that. Still noisy at any cycle. I've used to run my fans on variacs, but variacs are expensive and waste energy.

This very forum suggested to use a capacitor in series, which I have been doing for a while now. Cheap, quiet and efficient single speed solution.

 

I want to move forward with this project. I appreciate all the thoughtful replies but I'm overloaded with info, especially given my lack of electronics experience.

Below I've summarized the various suggestions from this thread down to their respective basic ideas. Two or three of them are duplicate or similar and a couple seem somewhat experimental (which I'm OK with). Which method below seems like the most practical, preferably $200 or less?

1) use a DC motor and an ESC with a microcontroller
2) a semi-conductor, variable AC motor controller in the Fairchild App. note, AN-3006
3) an HVAC blower with a brushless dc motor
4) a reasonably priced variable speed drive package
5) possibly just reducing the supply voltage would slow the acceleration to the running speed
6) replace the motor with a universal (brushed) motor rated for the mains voltage
7) use PWM control to vary the speed
8) use a capacitor in series... cheap, quiet and efficient single speed solution

 

Most are over the $200 limit, but the Fairchild one may be the cheap choice.

 

I have installed speed controls for those "Whole House Fan" installations that were highly touted many years ago, and seldom used much. There are external variable speed drives that will fit in a single-wide standard electrical box. The ones that I installed came from the "GRAINGER" store, and cost about $35 USD a few years back. they were rated for up to a half HP motor, which all of the fans I have investigated had either 1/3 HP or 1/2HP ratings. When they were switched on separately while set for a lower speed, the acceleration took a while, it was not instant. I have seen similar speed controls at other distributors also. So that could be almost a "Plug and PLay"installation choice.