Powering 7.2V DC motor with Arduino Motor Shield rev3 and external power supply

Other Hardware Motors, Mechanics, Power and CNC
1

Hi Forum,

I have tried looking up the current :wink: problem i am facing but i could not find an answer anywhere so i turned to the arduino forum, hoping some kind soul might help me out.

DC motor : RS-545SH-4522 made by MABUCHI

Arduino Board: Arduino UNO rev3 + Arduino motor shield rev3

Power Supply : Ni-MH 14.4V-F. This is a battery pack i salvaged from a rechargable vacuum cleaner.

Problem: I could not power the 7.2V DC motor. I wired up the battery pack to the GND(Black Wire) and Vin(Red wire) screw in pins. The i connected the wires of the DC motor accordingly to Socket A ie. Red wire to A+ and black wire to A-.

const int motorDirB = 13;
const int motorSpeedPinB = 11;
const int motorBrakePinB = 8;


void setup() {
 pinMode(motorDirB,OUTPUT);
 pinMode(motorSpeedPinB, OUTPUT);
 pinMode(motorBrakePinB, OUTPUT);
}


void loop() {
  
digitalWrite(motorBrakePinB, LOW);
digitalWrite(motorDirB, HIGH); 
analogWrite(motorSpeedPinB, 255);

delay(5000);
digitalWrite(MotorBrakePinA, HIGH);
delay(200);

}

However, the DC motor does not spin, but it makes a vibrating noise. I then replaced it with a lower voltage DC Motor, which spins nicely. I removed the power supply and directly touched the wires of the 7.2V DC motor with the power supply and it spins.

Is the shield regulating the power supply? If so how do i solve this problem. I need a quite precise control of the various parameters of the 7.2 V DC motor such as its speed, direction and delay.

Thanks in advance ;D

2

The motor shield has a maximum current of around 2A. Depending on what load you have on your motor it is likely to want to run at between 5A and 15A, possibly more since you're also running it at twice its rated voltage.

See the problem? You need a much better motor driver. I'd look for one with at least 20A rating, maybe 30A.

Steve