External power supply for DK Electronics motor shield v1.0

Hi!

I am planning to use my Arduino Uno R3 to build a 4 wheel drive robot car. To control the motors, I’ve chosen a cheap motor shield by DK Electronics, which is a clone of the Adafruit Motor Shield v1.

I’m using a 4xAA battery pack with 4 rechargeable batteries, each 1.2 V and 2650 mAh. Since I need to power 4 motors with it, I connected the battery pack to a boost converter, and it outputs 9 volts. I’ve connected the battery pack to the EXT_PWR block and uploaded the example MotorTest:

// Adafruit Motor shield library
// copyright Adafruit Industries LLC, 2009
// this code is public domain, enjoy!

#include <AFMotor.h>

AF_DCMotor motor(4);

void setup() {
  Serial.begin(9600);           // set up Serial library at 9600 bps
  Serial.println("Motor test!");

  // turn on motor
  motor.setSpeed(200);
 
  motor.run(RELEASE);
}

void loop() {
  uint8_t i;
  
  Serial.print("tick");
  
  motor.run(FORWARD);
  for (i=0; i<255; i++) {
    motor.setSpeed(i);  
    delay(10);
 }
 
  for (i=255; i!=0; i--) {
    motor.setSpeed(i);  
    delay(10);
 }
  
  Serial.print("tock");

  motor.run(BACKWARD);
  for (i=0; i<255; i++) {
    motor.setSpeed(i);  
    delay(10);
 }
 
  for (i=255; i!=0; i--) {
    motor.setSpeed(i);  
    delay(10);
 }
  

  Serial.print("tech");
  motor.run(RELEASE);
  delay(1000);
}

The motor works perfectly.

However, I’ve encountered a problem when I was trying to power the shield without the USB cable from my laptop. The motor seems to have a tendency to spin and makes a sound for roughly a second, then the Arduino board resets. This goes on forever. The power jumper is attached to the shield, and it doesn’t work with any amount of motors.

I’ve tried detaching the boost converter, but I still encounter the problem mentioned above.

Any help will be appreciated.

Thanks,
Luke

Hi,
How are you powering the arduino board with the USB disconnected?
You could be getting a back feed from the motor supply, not good.

Tom... :slight_smile:

Hi Tom,

Thanks for your reply! I've followed the instructions from the Adafruit Motor Shield Power Requirements page:

If you would like to have a single DC power supply for the Arduino and motors, simply plug it into the DC jack on the Arduino or the 2-pin PWR_EXT block on the shield. Place the power jumper on the motor shield.

My Arduino also has the on light green.

Thanks,
Luke

Hi,

Use a DMM and measure the voltage coming out of your DC-DC converter when the fault is happening, it may not be able to supply the current for both the motors and the Arduino and you will notice the voltage drop, his will make the Arduino reset.

Then check the voltage of your batteries while this is happening, to see if they are able to supply the current required.

Tom... :slight_smile:

Hi Tom,

Thanks for your reply! Your description of the fault is correct. Instead of getting a 9 volt supply from the DC-DC converter, I get roughly 5 volts, and the battery supply's voltage drops to 3 volts.

Now I get the problem, but can you give me the instructions on how to fix it (I'm a newbie)?

Thanks,
Luke

Hi guys,

Does anyone know how to fix the problem that Tom has mentioned above?

Thanks,
Luke

Instead of getting a 9 volt supply from the DC-DC converter, I get roughly 5 volts, and the battery supply's voltage drops to 3 volts.

Think about that.
The first thing you need to do is eliminate your prime suspect, the dc-dc converter.
You need to replace it with a battery pack (preferably comprised of AA batteries) that supplies the same voltage you wanted from the dc to dc converter. If everything works properly when you do that then the only conclusion anyone can come to is that your dc-dc converter cannot supply the load you need and you have to use batteries.

If your board does not work without dc-dc converter, then maybe the battery bank does not have the capacity to run the whole system. maybe you should try with higher capacity (mah) batteries, or just try with a wall power supply. Just try, then if it is ok, i think your batteries cant feed the system. After you go so far, you should adjust your dc-dc converter to required settings.

You need to test it using 6 AA batteries and the "single supply " jumper installed.
This eliminates both the dc dc converter & the rechargable batteries. The dc dc converter lkkely can’t drive motors.

as I can shove an external voltage to the engines run, that with pure voltage arduino engines not only pure noise is heard move, they know if there is any diagram as connect an external source or how to fix this situation ??

as I can shove an external voltage to the engines run, that with pure voltage arduino engines not only pure noise is heard move, they know if there is any diagram as connect an external source or how to fix this situation ??

??? (translation ?)