To Build a Robot Part 4

I received my TLC 5940 NT from Texas instruments and immediately set it up to do a quick test with some LEDs which is always fun: LED Video

I was working on the initial setup while I was sick so I missed something very obvious about the design of my circuit. The TLC actually uses the Ground to produce the PWM wave where the Arduino uses the +. This means to have it turn on the H-Bridge you need to do a pull-up resistor so you can feed it with the 5v.

I used 2k resistors for the Pull-up and things worked well, when I went to 10k the motor slowed in reverse (no idea why right now ill investigate later)

Using this setup you can drive a very large number of motors. You can put the TLC5940 chips in series and control hundreds of motors. For the setup I have here you could control 2 motors per H-Bridge if you use the L293B (but get the L293D) like I have here. Since each motor only requires 2 pins you can control a maximum of 8 motors per TLC5940 chip if you also have 4 h-bridges. If you only need the DC Motor to spin in one direction you only need 1 Pin to control it and could then control 16 motors with variable speed.

Keep in mind the amperage when driving motors with the L293 series they all allow up to about 1 amp. Some motors are very powerful and can reach this limit quickly. Choose your H-Bridge wisely.

Docs and Datasheets:

TLC5940NT
L293B

The sketch uses the TLC library for the Arduino available here: TLC5940 Arduino Library

Image of the circuit

Arduino Controlling a TLC5940 using a L293B HBridge to drive a motor

The sketch just spins a motor forward for 1 second then breaks and backward for a second.

#include "Tlc5940.h"
boolean forward = false;

void setup()
{
  Tlc.init();
}

void loop()
{
    Tlc.clear();
    forward = !forward;
    if (forward) {
      // Brake
      Tlc.set(1, 0);
      Tlc.set(2, 0);
      Tlc.update();
      delay(500);

      // Go
      Tlc.set(1, 0);
      Tlc.set(2, 4095);
    } else {
      // Brake
      Tlc.set(1, 0);
      Tlc.set(2, 0);
      Tlc.update();
      delay(500);

      // Go
      Tlc.set(1, 4095);
      Tlc.set(2, 0);
    }
    Tlc.update();

    delay(1000);
}

Advertisements