Speed controler schematic

[patmurris]

Hi all!

I don't have speed control on my small lathe and although i can live without it, i'd be glad to have the added comfort. However, for what i've seen, the available devices cost almost as much as my lathe (around 400 dollars) so i'd like to build one myself.

I used to build simple electronic circuits long ago and i'm somewhat familiar with analog circuits and electronic components. My understanding is that such a circuit (to drive a single phase asynchronous motor) boils down to a rectifier (converts AC to DC) and a variable frequency oscillator which should amount to a rather limited number of components - something i would feel comfortable to build.

Now where do i find the schematic?

Any help or pointer will be appreciated! :wink:

Thanks

 

[KenV]

Pat -- My understanding is that you need a DC motor to work with such a circuit -- preferable a permanent magnet motor. Salvage from treadmills is one source and Penn State was selling a replacement set with controller for about $100. The motor form need to match your gear unless you are going to be making new mounts -- Unlikely that a NEMA 56 90 volt 1/2 or 3/4 HP motor will fit you lathe as a direct bolt in substitute.

I have one of the PSI motors for powering a micro metal lathe. It works OK but loses torque pretty fast if the motor speed drops below about 1/2 of the full speed. It was sold as a substitute for a Jet 1014.

If you want to go to Variable Frequency -- the electronics get very fancy fast -- and those are the $400 and more systems. Better speed control, chance to use three phase motors on single phase circuits and better torque response at slower motor speeds.