Below are a number of images showing the development of a Pulse Width Modulator (PWM)
Speed controller. The prototypes are now complete and is going through final
testing. The controller is designed to interface the Mach2 CNC control software (http://www.artofcnc.ca) or other software with the KB Electronics DC motor controllers as used in the Sherline DC motor speed controllers. Apart from the PWM input mode, it can also work using a Step/Dir, UP/DOWN or Synchronous Serial input. |
*** WARNING *** The KB Electronics DC speed controller circuit, and other similar speed controllers as found in Asian imported mini lathes and mini mills are at mains voltage potential. This voltage is lethal. Do not attempt to do this conversion if you are not confident and qualified to do so. |
This shows what can happen if you accidentally ground the controller board. I was
taking a voltage measurement during testing and a lead slipped, touching the grounded
case. I couple of the tracks sacrificed themselves by vaporising.
It set me back a couple of days will I repaired the controller. |
Two of the prototype PCBs are ready for the surface mount device (SMD) components
to be loaded. The boards are 80mm x 25mm in size and designed to fit into
a Sherline DC motor speed controller housing. |
The boards have been populated with the SMD components and are placed into the reflow
oven. |
This is the reflow oven. Its a converted fan-forced toaster oven. I replaced the
temperature controller with an accurate micro processor controlled temperature
controller. |
The two boards have been cooked and populated with the Through Hole Components (THC).
On the left is a mini-din connector that connects to the breakout board. The
switch is to select manual/ computer control. |
The first of the three prototypes is mounted inside a die-cast box with the KBMM
controller. |
This is how the unit is mounted on my Taig Mill. You can see the mini-din extension
cable leading from the speed controller can be seen on the bottom left. |