Introduction

• Controls two DC motors
• Rorward and reverse operation of each independently
• Supports pulse width modulation (PWM) for speed control
• Up to 2 amps per motor
• 12 to 46 volts motor supply, 5 volt logic supply
• Automatic thermal protection in case of overload
• Small size (less than 2x2x2")
• Under $30 cost
• Can also be used to drive stepper motors

Before you build:

• The LEDs are optional. They are just debugging indicators
• Choose R6 depending upon motor supply voltage, or omit D6, the motor supply indicator LED. Use 400 ohms or more for 12 volt supply. 1K works well.
• If you're going to use the optional current sending, bend up the two end leads (pin numbers 1 and 15) of the L298 and don't solder them to the board. Instead solder them to your current sensing resistors, and solder the other to the spare pads near the YAAARC legend. Choose the resistors so the maximum drop across the resister is less than 2 volts. Connect your "sense" leads to the junction of the resistor and the L298.

Assembly notes:

• The apparent solder bridge between pins 11 and 12 of the 74HC14 is actually a trace. Don't panic.
• For the 8 clamp diodes, make a "U" bend in the lead from the banded end of the diode body. This lead goes in the square hole. If you get any diodes in backwards, you will short out the Vs power supply.
• If you are installing LEDs, determine which lead should be positive for the LED to work, and orient the LEDs according to the "map" of the board.

Installation and Hookup:

• See the drawings for hookup information
• Y2MD requires +5V from the CPU connector. (J1, 10 pin header)
• Motor power (Vs)input and ground are on the output screw terminal strip.
• Motor ground and CPU ground are common, and are connected to the heatsink.
• If all LEDs are installed, with 220 ohm resistors, draw on Vcc (+5) could be 100ma. Omit the LEDs or use 1K resisters, 1206 size, for low-power applications.

Use:

Your CPU should set the direction bit high or low for a motor, and set the enable bit high to turn on the motor. Sequence is not critical -- you can change directionss without turning the motor off, etc.

Unused inputs (direction and enable) should be tied to ground or Vcc. Current draw will be lower if enable is grounded.

PWM can be done by toggling enable. Max PWM frequency is 25khz.

If the L298 gets hot, it will automatically reduce motor current to protect itself. It seems pretty bulletproof so far. Keep those robots rolling!

Y2MD was created for the Ypsilanti Ann Arbor Area Robotics Club (YAAARC) by Erik Kauppi, 01-01-96. Send e-mail to erik@hamjudo.com if you have questions.