Industrial automation continues to use smart controls like motion controllers, variable frequency drives (VFDs), and programmable logic controller (PLC) based motor drives. At the same time, desktop manufacturing systems are becoming popular for smaller manufacturers. The pick and place machines used in electronic manufacturing systems to place surface mount devices (SMDs) and assembly processes are typical for industrial automation manufacturers. Although VFDs or motion controllers are traditionally used for controlling AC or DC motors, the commutation nature of operation can be less efficient for the overall system. Also, cost can become a limiting factor for small manufacturing systems. In response, Maxon has developed a small form factor, one-quadrant motor controller solution to operate a brushless DC motor.
|The Maxon DEC Module evaluation board provides prototyping convenience for evaluating the module 24/2 or precision brushless DC motors. (Image source: Maxon)|
Commutators Vs. Brushless DC Motors
Traditional motors have a segmented rotating cylinder with multiple metal contacts on the rotor. An electromagnet coil with windings is attached to the rotor as well. Graphite-like brushes are pressed against the stationary contacts. As the rotor turns, electrical current is applied to the motor’s windings. As the commutator reverses the electrical current direction, the magnetic field creates torque in the opposing direction. This constant rotation contact to the commutator and brushes can easily shorten the motor’s life expectancy. With such failures as mechanical wear to the brushes and power losses attributed to internal I2R inefficiencies, the commutator has been replaced by brushless methods.
Brushless DC motors use an inverter or switching power supply, which drives each phase of the motor. Typically, brushless DC motors have three windings like an AC synchronous motor. Pulses of current are applied to the brushless DC motor’s windings. The number of coil windings determine the poles of the motor. Usually, brushless DC motors have four poles. Control of the motor’s speed and torque can be operated efficiently and effectively as compared to a commutator-based DC motor. With such precision control, the life expectancy of the brushless DC motor is longer compared to a traditional commutator device.
Getting the most efficiency out of a brushless DC motor requires a digital controller. Maxon has developed an Electronic Control (EC) amplifier-based digital controller to operate brushless DC motors. The module DEC 24/2 (Digital EC Controller) is a small form factor unit (20.38mm x 24.2mm) capable of driving brushless DC motors consuming 48W of power. The module 24/2 is a 1-quadrant controller capable of accelerating a brushless DC motor’s speed and torque in the same direction. It can drive motors up to a speed of 80,000 rpm. Three speeds can be selected using two digital input pins. The binary combinations of 1 and 0 can select the three speeds of the digital controller. The module 24/2 also can change a brushless DC motor's direction of rotation using a similar binary signal speed selection scheme.
|The Maxon DEC Module 24/2 digital controller speed can be adjusted using two digital input pins. (Image source: Maxon)|
Maxon 1-Q-EC Amplifier DEC Module 24/2
The module 24/2 has a nominal operating voltage range of 8 to 24VDC. A +5VDC supply is possible to operate the digital controller, according to Maxon’s datasheet. The output driver of the controller can source +5VDC with a maximum current of 35A. Maxon’s brushless DC motors, such as the ECX Speed 8M or EC-4 pole, can easily be driven using the module 24/2. Another important feature is the enabling and disabling of the digital controller’s output stage.
This feature can be useful when troubleshooting a motion controller device or system. Instead of powering down the controller completely, the output can be disabled. There are also protective functional devices, such as undervoltage, overvoltage, and thermal overload, embedded within the digital controller. To make the prototyping development of brushless DC motor applications convenient, Maxon has provided a DEC Module evaluation board, Part Number 370652.
Don Wilcher is a passionate teacher of electronics technology and an electrical engineer with 26 years of industrial experience. He’s worked on industrial robotics systems, automotive electronic modules/systems, and embedded wireless controls for small consumer appliances. He’s also a book author, writing DIY project books on electronics and robotics technologies.
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