When building a DIY motor control and power switching system, it's essential to ensure that the components you use can handle the required power levels while also offering precision and reliability. For this project, we'll be focusing on utilizing the TD62C950RF—a high-performance transistor array from Toshiba. This device is ideal for controlling DC motors, relays, and other high-power loads, as it combines multiple transistor switches in a single integrated package, making it a practical solution for power switching applications.
Objective
In this project, we will design a motor control circuit that uses the TD62C950RF to control the operation of a small DC motor. The system will provide the flexibility to switch the motor on and off, as well as to reverse its direction for bidirectional motor control. The TD62C950RF will act as the central power switching element, responsible for switching the motor's power and direction.
Components Required
● TD62C950RF: A Darlington transistor array with integrated flyback diodes.
● DC Motor: A small 12V DC motor.
● H-Bridge: The core component for controlling the direction of the motor.
● Power Supply: A 12V DC power supply capable of driving the motor.
● Push Buttons: To control the start, stop, and direction of the motor.
● Diodes: To protect the circuit from voltage spikes caused by inductive loads like motors.
● Resistors: For limiting current where necessary.
● Capacitors: To smooth out voltage fluctuations.
● Heat Sink: To dissipate heat from the transistors in the TD62C950RF.
The TD62C950RF Overview
The TD62C950RF is a high-voltage transistor array. It features Darlington transistors, which provide higher current gain and the ability to switch larger currents compared to standard transistors. Additionally, the TD62C950RF has integrated flyback diodes, which are essential for protecting the transistors when switching inductive loads like motors.
The TD62C950RF comes in an 18-pin package, and it includes 8 Darlington pairs—each capable of switching high current loads. These pairs can be used to control multiple components, making it a versatile choice for motor control and power switching.
Circuit Design
For the motor control system, we'll design a bidirectional motor control circuit, meaning the motor can be rotated in both directions. This will be achieved by using an H-Bridge configuration. The H-Bridge is an arrangement of four switches (transistors) that allows current to flow in either direction through the motor, enabling bidirectional control.
Step 1: Basic Motor Control Setup
Start by connecting the motor to the H-Bridge made from the TD62C950RF transistors. The four switching elements in the H-Bridge will be controlled by the push buttons to provide the desired motion for the motor.
Motor Connection: The two terminals of the motor are connected to the outputs of the H-Bridge.
Power Supply: The 12V power supply is connected to the common rail of the H-Bridge.
Flyback Diodes: Since motors are inductive loads, flyback diodes are essential for protecting the switching transistors when the motor stops or changes direction. The TD62C950RF has these integrated, so you don’t need to add extra diodes.
Step 2: Control Buttons
The circuit will have three push buttons:
● Start Button: To turn the motor on.
● Stop Button: To turn the motor off.
● Direction Button: To change the direction of the motor (i.e., forward or reverse).
These buttons will be connected to the inputs of the TD62C950RF transistor array. The array's output pins will control the H-Bridge transistors, turning them on or off depending on the button pressed. The direction of the motor is determined by which diagonal pair of transistors in the H-Bridge is turned on.
Step 3: Power Switching Using the TD62C950RF
The TD62C950RF is the key component for power switching. It allows you to control the flow of current to the motor, ensuring that the correct direction is achieved. Here’s how the TD62C950RF fits into the circuit:
The input pins (pins 1 to 8) of the TD62C950RF will be connected to the control buttons.
The output pins (pins 9 to 16) will be connected to the transistors in the H-Bridge.
The ground pins (pins 17 and 18) will be connected to the negative side of the power supply.
Flyback Diodes: These are built into the TD62C950RF, so no additional diodes are needed in the circuit for protecting the transistors from back EMF generated by the motor.
By pressing the Start Button, the relevant input pins on the TD62C950RF will be activated, switching on the corresponding output transistors that feed power to the motor.
Step 4: Direction Control
To reverse the motor's direction, the Direction Button will switch the connections in the H-Bridge. When the button is pressed, the opposite pair of transistors will be switched on, causing the motor to rotate in the opposite direction.
For example:
● Pressing the Start Button while the Direction Button is not pressed will turn on transistors that allow current to flow through the motor in one direction (say, forward).
● Pressing the Direction Button and then pressing the Start Button will turn on the opposite pair of transistors, changing the current flow and reversing the motor’s direction.
Step 5: Adding the Stop Button
The Stop Button will be connected to the input pins of the TD62C950RF to disable all the output transistors. This will disconnect the motor from the power supply and stop it from rotating.
Step 6: Heat Dissipation
Since the TD62C950RF transistors handle significant current and power, they may generate heat. To prevent overheating, it’s a good idea to attach a heat sink to the TD62C950RF to ensure it operates within its safe thermal limits.
Testing and Troubleshooting
Once the circuit is wired up, you can begin testing the system. Follow these steps:
Power the circuit with the 12V DC supply.
Press the Start Button and check if the motor begins rotating in the desired direction.
Press the Direction Button and observe if the motor changes direction accordingly.
Press the Stop Button to ensure the motor stops.
If the motor does not operate correctly:
● Double-check the connections to the TD62C950RF.
● Ensure that the H-Bridge configuration is correct.
● Verify that the flyback diodes are functioning properly to protect the transistors from voltage spikes.
Conclusion
This DIY motor control and power switching system using the TD62C950RF provides a straightforward, efficient way to control a DC motor in both directions. By leveraging the high-current switching capabilities of the TD62C950RF transistor array, we can create a reliable and cost-effective motor control circuit suitable for various applications, from robotics to automation systems.
This project demonstrates how to integrate a transistor array like the TD62C950RF in a practical application, providing smooth, reliable switching for both power control and motor direction in a simple H-Bridge configuration. The use of integrated flyback diodes makes the design simpler and more robust, while the addition of control buttons ensures user-friendly operation.