Let's Make Robots!

Control your motors with L293D

UPDATE

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update 26/4/09
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My 1st instructable  :)

http://www.instructables.com/id/HiTec-Servo-Hack/

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After long research and trial and error,  I´ve came up to a new walkthrough regarding this nice chip, the L293D.

Each project is one project and each one has its own unique power configurations, so you must be aware of the best battery choice and how to distribute voltage through your robot.

I strongly advice you to read the following articles:

Picking Batteries for your Robot
Once you’ve decided on batteries, how do you regulate the voltage

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L293D gives you the possibility to control two motors in both directions - datasheet

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The L293D Circuit:

Basic Implementation:

This is the most basic implementation of the chip.

As you can see, a 5V Voltage Regulator is between the battery and pins 1, 9, 16.

Pin 8 gets power before the VReg, if your motor needs for example 6V you should put 6V directly in this pin, all the other pins should not get more than 5V.

This will work with no problem at all, but if you want to do the right implementation take a look at the next example:

3235657956_b3be2b4f2f.jpg?v=0

3262168342_ae12307934.jpg?v=1240780647

This is the correct Implementation (with the capacitors), and note that pin 8 is feeded by unregulated voltage. This means that if your motors need more than 5V, you should power this pin with that amount of voltage, and the rest of the circuit with 5V.

3235658022_f78495fddd.jpg?v=0
The capacitors stabilize the current.

The same circuit on a breadboard:
3252941552_2f4919475f.jpg?v=1240780044

Soldered on a pcb and ready to go:
3234563157_780312a389.jpg?v=0
3451483356_2fdf26be19.jpg?v=0

3257970545_12de4f710e.jpg?v=0

This is the back of the circuit, click for high resolution photo.

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CODE
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// Use this code to test your motor with the Arduino board:

// if you need PWM, just use the PWM outputs on the Arduino
// and instead of digitalWrite, you should use the analogWrite command

// —————————————————————————  Motors
int motor_left[] = {2, 3};
int motor_right[] = {7, 8};

// ————————————————————————— Setup
void setup() {
Serial.begin(9600);

// Setup motors
int i;
for(i = 0; i < 2; i++){
pinMode(motor_left[i], OUTPUT);
pinMode(motor_right[i], OUTPUT);
}

}

// ————————————————————————— Loop
void loop() {

drive_forward();
delay(1000);
motor_stop();
Serial.println(”1″);

drive_backward();
delay(1000);
motor_stop();
Serial.println(”2″);

turn_left();
delay(1000);
motor_stop();
Serial.println(”3″);

turn_right();
delay(1000);
motor_stop();
Serial.println(”4″);

motor_stop();
delay(1000);
motor_stop();
Serial.println(”5″);
}

// ————————————————————————— Drive

void motor_stop(){
digitalWrite(motor_left[0], LOW);
digitalWrite(motor_left[1], LOW);

digitalWrite(motor_right[0], LOW);
digitalWrite(motor_right[1], LOW);
delay(25);
}

void drive_forward(){
digitalWrite(motor_left[0], HIGH);
digitalWrite(motor_left[1], LOW);

digitalWrite(motor_right[0], HIGH);
digitalWrite(motor_right[1], LOW);
}

void drive_backward(){
digitalWrite(motor_left[0], LOW);
digitalWrite(motor_left[1], HIGH);

digitalWrite(motor_right[0], LOW);
digitalWrite(motor_right[1], HIGH);
}

void turn_left(){
digitalWrite(motor_left[0], LOW);
digitalWrite(motor_left[1], HIGH);

digitalWrite(motor_right[0], HIGH);
digitalWrite(motor_right[1], LOW);
}

void turn_right(){
digitalWrite(motor_left[0], HIGH);
digitalWrite(motor_left[1], LOW);

digitalWrite(motor_right[0], LOW);
digitalWrite(motor_right[1], HIGH);
}

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You can also get non-polarised electrolytics, which naturally have no (+) sign at all =D

You're just saying that to confuse me :D
There are other non-polarised types too, such as polyester, aluminium foil, green caps...
At the end of the day only a few things really matter for most uses: capacitance, maximum voltage and polarity. Sometimes you'll need to know the equivalent series resistance, leakage rate, or other details but normally you don't worry about them.

"There are other non-polarised types too, such as polyester, aluminium foil, green caps..."

doh.jpeg

They're probably Tantalum caps, judging from the appearance, value and polarisation.

HOW can you tell it's a tantalum cap judging from the appearance, value and polarisation?

According to the diagram they're NOT polarized (tantalums are). The value could be both ceramic and tantalum (or am I wrong?). And the appearences of the two types are extremely similar...

Damnit I think you're right. The 3rd kind I allways forget. Another noob mistake on my part. Man it isn't easy learning electronics. A lot of incomplete or wrong information around. Guess I'll have to find a better symbol list.

Besides these things look VERY similar to the ceramic ones :|

i connect everything like on the first breadboard-picture.

whit one motor everything is ok. but with two there is this problem. and i dont think it is the batterie cause it works but not in different ways.. together they drive in the same direction but in diffent ways not. in the serial monitor left and right doesnt appear ???

how are you powering your motors and microcontroller?
Tomorow I will buy a batterie case... then I can give you more information.. until now i only powered the µC over usb.. is this a fault?