Motor Control Circuits

An opto-interrupter made with Lego beams, regular parts, a 6 hole pulley wheel and an axle.

The fan, motor controller and batteries are mounted to the bottom board, so that the fan system can be wired up and tested before assembly. Once the fan system is tested the top board and bottom board can be brought together to form the hovercraft plenum chamber. The segmented skirt attaches between the top and bottom board, to channel the air from the chamber under the board. And there you have it, as simple as that!!!??? It is a good idea to build an in emergency cut-out to the motor controller to stop the fan if the rider falls off the board.

This application note demonstrates the use of a PIC17C756A microcontroller (MCU) in a brush-DC servomotor application. The PIC17CXXX family of micro-controllers makes an excellent choice for cost-effective embedded servomotor control applications. Some of the benefits of the PIC17CXXX MCU family include fast instruction cycle execution (up to 120 ns), an 8 x 8 hardware multiplier, and many useful hardware peripherals.

Microchip's TC642, TC643, and TC646 are the world's first integrated circuits dedicated for controlling and monitoring fan speed. The new family of fan speed controllers modulate fan speed to compensate for changes in system temperature. This means the fan runs at full speed only when necessary, significantly extending fan life. In addition to increased fan life, fan speed is controlled by PWM control circuitry that is more efficient than conventional linear techniques. The ICs provide other features such as fan current limiting, minimum speed control, auto shutdown, and speed, fault, and over-temperature indication.

PWM fan speed control methodology pulse-width modulates a fan?s full-rated power supply voltage at a low frequency, typically 30Hz. A typical PWM circuit, consisting of a transistor in series with a fan, can be small and inexpensive because it is either fully on or completely off. This efficient control methodology affords a very wide speed control range (typically 10% to 100% of full speed) because the fan motor is exposed to its full-rated voltage during the active portion of the PWM cycle.

The NLX Power Supply Specification released by Intel Corp. defines the requirements for next-generation PC system power supplies. There are several enhancements outlined in this specification as compared to the ?old? PS/2 power supply form factor. One of these features is control and monitoring of the cooling fan(s) inside the NLX power supply. The NLX specification designates two interface fan control signals: 1. FanM signal is an output from the NLX-compliant power supply.

Fan speed control extends fan service life and decreases acoustic airflow noise and average fan current. The most efficient way to implement fan speed control is to use low frequency pulse width modulation (PWM). However, PWM fan speed control can sometimes introduce unwanted acoustic noise at a frequency equal to that of the PWM itself. This is especially noticeable when PWM control is used with higher operating current (>300 mA) fans and at low operating speeds. This application note discusses the source of this acoustic noise and a method to suppress it.

Two low-cost CMOS ICs manage a 12 VDC, current-limited speed control circuit for DC brush motors. The circuit design (see Figure 1) uses PWM (pulse width modulation) to chop the effective input voltage to the motor. Use of CMOS devices gives the benefits of low power, minimal heat and improved longevity. The overall design is simple, inexpensive and reliable, and is useful in applications such as embedded DC motor control where efficiency, economy and performance are essential.

Brushless DC fan speed can be varied using pulse-width modulation (PWM). The typical PWM control scheme inserts a power switch in series with the fan as shown in Figure 1. In such applications, an increase in the active duty cycle causes a corresponding increase in fan speed (i.e., fan speed is proportional to tON/(tON + tOFF). Conventional wisdom states that PWM duty cycle alone determines operating speed (for example, the fan speed runs at 50% of maximum when the PWM duty cycle is 50%). In reality, the fan operates at a higher percentage of full speed for any given duty cycle. The resulting difference between actual fan speed and the corresponding PWM duty cycle (herein referred to as Speed Error) can be problematic in open loop fan control systems.

Brushed DC motors are widely used in applications ranging from toys to push-button adjustable car seats. Brushed DC (BDC) motors are inexpensive, easy to drive, and are readily available in all sizes and shapes. This application note will discuss how a BDC motor works, how to drive a BDC motor, and how a drive circuit can be interfaced to a PIC® microcontroller.

Brushless Direct Current (BLDC) motors are one of the motor types rapidly gaining popularity. BLDC motors are used in industries such as Appliances, Automotive, Aerospace, Consumer, Medical, Industrial Automation Equipment and Instrumentation. As the name implies, BLDC motors do not use brushes for commutation; instead, they are electronically commutated. BLDC motors have many advantages over brushed DC motors and induction motors.

This application note discusses the steps of developing several controllers for brushless motors. We cover sensored, sensorless, open loop, and closed loop design. There is even a controller with independent voltage and speed controls so you can discover your motor's characteristic's empirically.

The PIC18F2331/2431/4331/4431 family of microcontrollers have peripherals that are suitable for motor control applications. In this application note, we will see how to use these features to control a Brushless DC (BLDC) motor in open loop and in closed loop. Refer to the Microchip application note, “AN885, Brushless DC (BLDC) Motor Fundamentals” (DS00885), for working principles of Brushless DC motors and basics of control. Also, to obtain more information on motor control peripherals and their functions, refer to the PIC18F2331/2431/4331/4431

Single-phase induction motors are extensively used in appliances and industrial controls. The Permanent Split Capacitor (PSC) single-phase induction motor is the simplest and most widely used motor of this type. The classification, construction and working principle of single-phase induction motors are explained in detail in the application note "AC Induction Motor Fundamentals" (AN887) available from Microchip.

This application note demonstrates the use of a PIC17C756A microcontroller (MCU) in a brush-DC servomotor application. The PIC17CXXX family of micro-controllers makes an excellent choice for cost-effective embedded servomotor control applications. Some of the benefits of the PIC17CXXX MCU family include fast instruction cycle execution (up to 120 ns), an 8 x 8 hardware multiplier, and many useful hardware peripherals.

This application note describes how the PIC18F4431 may be used to control an ACIM using open and closed-loop V/f control strategies. The application code is built incrementally and demonstrates the following control methods: 1. Voltage-frequency (V/f) control 2. Voltage-frequency control with current feedback 3. Voltage-frequency control with velocity feedback and PID control The PIC18F4431 incorporates a set of innovative peripherals, designed especially for motor control applications. The utility of these peripherals is demonstrated in both open and closed-loop three-phase ACIM motor applications. It is assumed that the reader is already familiar with the theory and nomenclature of AC induction motors. For an excellent introduction to the basic concepts of induction motors control, please refer to Microchip?s application note AN887, ?AC Induction Motor Fundamentals?

PWM fan speed control methodology pulse-width modulates a fan?s full-rated power supply voltage at a low frequency, typically 30Hz. A typical PWM circuit, consisting of a transistor in series with a fan, can be small and inexpensive because it is either fully on or completely off. This efficient control methodology affords a very wide speed control range (typically 10% to 100% of full speed) because the fan motor is exposed to its full-rated voltage during the active portion of the PWM cycle.

This application note discusses how to use the Enhanced, Capture, Compare, PWM (ECCP) on the PIC16F684 for bidirectional, brushed DC (BDC) motor control. Low-cost brushed DC motor control can be used in applications such as intelligent toys, small appliances and power tools. The PIC16F684 takes Microchip's Mid-Range Family of products to the next level with its new ECCP periperal.

Sensors are a critical component in a motor control system. They are used to sense the current, position, speed and direction of the rotating motor. Recent advancements in sensor technology have improved the accuracy and reliability of sensors, while reducing the cost. Many sensors are now available that integrate the sensor and signal-conditioning circuitry into a single package.

Certain applications, such as file servers, require redundant cooling fans to ensure uninterrupted system service, even with cooling fan malfunctions present. Typically, such systems have a primary fan to cool the system, and one or more ?standby? fans that automatically are placed in service should the primary fan fail.