Motor and Controller Assembly

 

The slot car motor that Jerry used in his original drill press is long since gone and can occasionally be found on EBay for stupid amounts of money.

Looking around I found a very suitable, albeit larger, motor at the Hobby Depot shop up the street from the house.  With the emailed 45% off one item, one day only sale, the out the door price was under $9.  Distributed by Stevens International you can't buy direct but most hobby shops should be able to obtain it for you.  SVM540  $14.95

The motor is rated 4.5 to 12 VDC and will turn 17,500 rpm no load at 12VDC.  My plans are to drive it with a PWM DC motor controller that I picked up on Amazon.

Driving it with the PWM controller has the advantage of giving nearly full torque at low RPM's.  If you put a meter across the motor leads, the voltage will read 12V at any speed setting, however the amount of ON vs OFF time will vary.  Lots of ON and little OFF is high speed and lots of OFF and little ON will give low speed.

Also added to the electronics is a 12V to 6V 3A buck convertor to drive the electro magnet, greatly simplifying the power supply.  I plan to use an old laptop power supply to run the whole thing.

added 7/16/2016

I started to build the power supply box.  The cabinet will contain the PWM controller board, the 6V buck convertor for the magnet and the various controls.

Motor Control Box

This view shows the Pulse Width motor controller on the right and the 6v buck convertor for the electromagnet on the left.  Controls (L-R) are Magnet on/off & indicator, main power indicator & switch, motor on/off and the speed adjustment pot.

Polarized Connector

I made up a unique connector for the Motor and Magnet using Anderson PowerPoles.  Coaxial connector is the 12VDC input.

Control Box Face

Decals were made using my laser printer and installed.  In this shot they have not set completely.

added 7/24/2016