3 DC Motors & motorshield problem

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vinschni
 
Posts: 5
Joined: Tue Jan 04, 2011 5:42 pm

3 DC Motors & motorshield problem

Post by vinschni »

Hello together,
I'm using an Arduino Mega2560 with the Adafruit MotorShield I connected the following: I supply power through a laptop power adapter with 19V & 3.42A. Starting all three motors results something strange. The two motors run as they should. The single motor increases speed for ~2s and then suddenly shuts down, as if it would lose power. We meassured the current and it actually seems to break down towards zero. If we're using only the problematic motor and detach the other objects it works fine.

Simplifyed as much as possible the simplest setup without sensors/servo the following code results the problem:

Code: Select all

#include <AFMotor.h>
#include <Servo.h>

AF_DCMotor motor1(2);
AF_DCMotor motor2(3);
AF_DCMotor maeh_motor(4);

void setup()
{  
   motor1.setSpeed(250);
   motor2.setSpeed(250);
   maeh_motor.setSpeed(170);	
}

void loop()
{  
  maeh_motor.run(FORWARD);
  motor1.run(FORWARD);
  motor2.run(FORWARD);
}
Greetings,

Vinschni

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adafruit_support_bill
 
Posts: 88086
Joined: Sat Feb 07, 2009 10:11 am

Re: 3 DC Motors & motorshield problem

Post by adafruit_support_bill »

The single motor increases speed for ~2s and then suddenly shuts down,
If I understand the German correctly, the "single motor" is rated for 3 - 9 V/DC @0.8 A. This is already more than the 0.6A that the L293D H-bridge chips are rated for. And running them at 19V, the current draw will be about 2x that value. It sounds like the L293D chip is going into thermal shutdown. That would explain the loss of power.

At 19V, you motor is probably going to want about 1.6A. (Please understand that it will have a reduced life expectancy at this voltage.) To get that current, you would need to piggyback at least 3 L293D's or 2 SN754410 chips.

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