This is the revision C version of the MiniMotor2 module.

MiniMotor2 Module (Revision C)

1. Introduction
2. Programming
3. Hardware
- 3.1 Circuit Schematic
  - 3.1.1 Logic Schematic
  - 3.1.2 Power Schematic
- 3.2 Printed Circuit Board
4. Software
5. Issues

1. Introduction

The MiniMotor2 module is designed to drive two small (aka mini) sized motors with a maximum current of 600 mA per motor and maximum surge current of 1.2A. The logic circuitry is electrically isolated from the motor H-bridges the via optoisolators.

2. Programming

Basically there are two motors that can be controled -- Motor0 and Motor1.

The speed ranges from -128 to 127. The Programming Table has all of the available programming commands.

For those of you that program in Easy-C there is libarary of controller routines.

3. Hardware

The hardware consists of a circuit schematic and a printed circuit board. There is a separate parts list file.

3.1 Circuit Schematic

The circuit schematic is broken into to diagrams. The parts list kept in a separate file -- minimotor2.ptl.

3.1.1 Logic Schematic

The logic section of the MiniMotor2 module is shown below:

The logic power and CAN signals come in from N1 pins 3 through 8. The CAN signals are connected to the MCP2551 CAN physical layer IC, U1. The transmit and receive pins of the microctroller, (U2 pins 5 and 6) are connected to the other side of U1. Lastly, the RC0 through RC3 are used to drive the quad optoislator, U3, through current limiting resistors R5 through R7.

3.1.1 Power Schematic

Please note that U3 optoisolator shows up in both schematics. There is only one optoisolator, it is just easier to understand what is going on if the optoisolator is present in both schematics. There is no shared ground between the two sides of the optoisolator.

The power section of the MiniMotor2 module is shown below:

The power to drive everything can come from either an external battery at N4 or from the bus at N1. Switch S1 selects between the two possible power sources. Capacitor C3 (.1µF) and C4 (220µF) attempt to filter out any noise from the power source. The power is fed into a 5V low drop out voltage regulator (VR1) and the output is fed into C5 (22µF) to provide a stable 5V power supply for the H-bridge chip (U4). The opto-isolator chip (U3) outputs are fed to the inputs of U4 (IN1-4) to control the H-bridge. Resistors R1-4 are pull-up resistors. The enable pins for U4 are tied high. Motor 1 is connected to N2 and motor 2 is connected to N3. Capacitors C6 and C7 attempt to filter out high frequency noise coming back from the motors.

3.2 Printed Circuit Board

The printed circuit board files are listed below:

minimotor2_back.png: The solder side layer.
minimotor2_front.png: The component side layer.
minimotor2_artwork.png: The artwork layer.
minimotor2.gbl: The RS-274X "Gerber" back (solder side) layer.
minimotor2.gtl: The RS-274X "Gerber" top (component side) layer.
minimotor2.gal: The RS-274X "Gerber" artwork layer.
minimotor2.gml: The RS-274X "Gerber" mask layer.
minimotor2.drl: The "Excellon" NC drill file.
minimotor2.tol: The "Excellon" tool rack file.

4. Software

The following files are available:

minimotor2.ucl: The MiniMotor2 µCL source code. There is not much actual code here, since most code is implemented in libraries.
minimotor2.asm: The MiniMotor2 assembly code listing
minimotor2.lst: The MiniMotor2 assembly listing file.
minimotor2.hex: The µCL MiniMotor2 Intel^® Hex file.

5. Issues

The following fabrication issues came up:

The SN754410 is pin compatible with the L293D but has 1.1A current capacity as to the L239D'S .6A current capacity.