BLDC Drivers and Automation
This is the original BLDC driver board used in Precision Mathews and Weiss mills and lathes. Apparently it exists in two versions: for 220V and for 110V power. The 220V has simple bridge rectifier, and 110V uses voltage doubling to get ~280V DC power for the motor.
Once assembled, they mold it in epoxy for protection. However, it is not repairable anymore, and the only way to fix the machine when the driver breaks is to replace it as a module - sometimes $200-300 exercise
This is a set sold by AliExpress - a driver, a potentiometer for speed control, the clock-wise/counter-clockwise run switch, a tachometer and a motor. Note that tachometer only takes 5VDC from the board, and has its own Hall-effect sensor for picking up pulses from rotating magnet. These are not used as a feedback to control speed.
The connector pinout is shown above. The speed is controlled by the voltage (0..+5V) applied to Wiper terminal. The motor runs when either CW or CCW pin is pulled low; they both are pulled up to +5V when motor is stopped. Three Hall-effect rotor sensors are powered by +5V present on 5-pin connector. Some controllers have optional brake resistor controlled by the switch which looks as late modification circuit.
In my version (from Weiss WBL-290VF lathe) this switch is shown in the picture; the 300W power resistor is connected through the 20A600V IGBT. The green terminal block is going to resistor.
The above picture shows the resistor and driver in the electrical compartment of the lathe.
I did several improvements for my mill and lathe. The BLDC is very manageable and can be quickly stopped. This allows to make a simple magnetic sensor stop on the compound of the lathe, and also control the number of spindle spins and automatically stop. It is very handy for cutting threads to limit the depth of the tap and die, or run length of a cutting tool.
Since all control signals on the driver are not isolated from mains power, one has to use a pair of opto-couplers to bring the control inputs to safe, ground referenced signals controlled by a cheap microcontroller.
{ Description to follow }