[modeleng] Re: 12V variable speed power supply

Hello Julian and Rich

Thank you again for your sage advice.   I tried out the dimmer switch 
set-up, and as you predicted, it lost torque at low speeds.

Last evening, looking through ME adverts, I saw an easy answer to my 
problem - A Proxxon  power supply unit NG 5/E.   As it is such a beautiful 
day, I drove from St Albans to Dunstable to visit Chronos.   This power 
supply produces 12V DC with 5A capacity.      It has thyristor electronic 
speed control (with feedback) and does not lose torque on the lowest speeds. 
It is a very neat looking job.

Unfortunately I have no knowledge of electronics and am therefore, at my 
great age, unable to assemble components.   Had I this knowledge, I would 
have dispensed with screwcutting by gears, used a stepper motor and 
controller, (suitably programmed) to produce an infinity of screw threads 
and fine feeds..   Two rotary encoders would ensure that the mandrel and 
leadscrew were always in synch.    As I had no-one to help me set up this 
most desirable system, I have opted for a conventional change-wheel 
screw-cutting system and the variable feed as mentioned above.

Rich - if you DO make a mod to your Hobbymat, I think that the Proxxon is an 
idiot-proof, neat and successful, and relatively inexpensive method.    It 
does what it says on the box!

I thank all friends who have contacted me.    What a wonderful, friendly and 
helpful List!

I am glad to see that my original message has cleared the 'block' and that 
there have been so many messages over the past few days.   I get quite 
lonely when the messages dry up!

Cheers!   Hubert


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