uln2003 board and stepper motor 28BYJ-48

Projects Programming
1

I am trying to get one of these working.
It uses a ULN 2003a chip.

This simple programme

int Pin0 = 8; 
int Pin1 = 9; 
int Pin2 = 10; 
int Pin3 = 11; 
int _step = 0; 
boolean dir = false;
void setup() 
{ 
 pinMode(Pin0, OUTPUT);  
 pinMode(Pin1, OUTPUT);  
 pinMode(Pin2, OUTPUT);  
 pinMode(Pin3, OUTPUT);  
} 
 void loop() 
{ 
 switch(_step){ 
   case 0: 
     digitalWrite(Pin0, LOW);  
     digitalWrite(Pin1, LOW); 
     digitalWrite(Pin2, LOW); 
     digitalWrite(Pin3, HIGH); 
   break;  
   case 1: 
     digitalWrite(Pin0, LOW);  
     digitalWrite(Pin1, LOW); 
     digitalWrite(Pin2, HIGH); 
     digitalWrite(Pin3, HIGH); 
   break;  
   case 2: 
     digitalWrite(Pin0, LOW);  
     digitalWrite(Pin1, LOW); 
     digitalWrite(Pin2, HIGH); 
     digitalWrite(Pin3, LOW); 
   break;  
   case 3: 
     digitalWrite(Pin0, LOW);  
     digitalWrite(Pin1, HIGH); 
     digitalWrite(Pin2, HIGH); 
     digitalWrite(Pin3, LOW); 
   break;  
   case 4: 
     digitalWrite(Pin0, LOW);  
     digitalWrite(Pin1, HIGH); 
     digitalWrite(Pin2, LOW); 
     digitalWrite(Pin3, LOW); 
   break;  
   case 5: 
     digitalWrite(Pin0, HIGH);  
     digitalWrite(Pin1, HIGH); 
     digitalWrite(Pin2, LOW); 
     digitalWrite(Pin3, LOW); 
   break;  
     case 6: 
     digitalWrite(Pin0, HIGH);  
     digitalWrite(Pin1, LOW); 
     digitalWrite(Pin2, LOW); 
     digitalWrite(Pin3, LOW); 
   break;  
   case 7: 
     digitalWrite(Pin0, HIGH);  
     digitalWrite(Pin1, LOW); 
     digitalWrite(Pin2, LOW); 
     digitalWrite(Pin3, HIGH); 
   break;  
   default: 
     digitalWrite(Pin0, LOW);  
     digitalWrite(Pin1, LOW); 
     digitalWrite(Pin2, LOW); 
     digitalWrite(Pin3, LOW); 
   break;  
 } 
 if(dir){ 
   _step++; 
 }else{ 
   _step--; 
 } 
 if(_step>7){ 
   _step=0; 
 } 
 if(_step<0){ 
   _step=7; 
 } 
 delay(1); 
}

Seems to work fine. If I change the 'dir' to true the direction changes
It takes about 10 seconds to do a full circle.
If I open the 'stepper_oneRevolution' from the examples it seems to just hunt around the same spot as if it is not getting the right sequence of pulses.
The driver is plugged into the same arduino outputs for both sketches
Does anyone know what I am doing wrong?

2

See:
https://forum.arduino.cc/index.php?topic=364156.0

.

3

I think my problem was finding the URL?

4

How are you powering it?
ULN2003 has a lot of voltage drop across it, is not a great part for driving a motor from a low voltage source.

5

See this link:
https://arduino-info.wikispaces.com/SmallSteppers

.

6

Crossroads, when I saw your reply I went back and checked. I was running it from the usb supply but I have since changed it and added a 12v supply to the input of the arduino and the supply pin to the uln 2003a board from the vin socket next to the two gnd sockets on the arduino with no change.

I will take a look at the smallsteppers link.

7

At 31Ω per coil, that would be to hard on a USB power supply.

.

8

The simple program works better on the 12v supply .
The link you gave me makes reference to the fact that the sequence should be 8,10,9,11 so I changed the program to that and it has made a difference, it looks like it might be working now but the motor has such a large gear reduction ratio that it is hardy moving. I tried it with the program set to 2048 as suggested in the link but all I get is buzzing, maybe it can't handle them that quick. I am to my bed now but will take another look tomorrow.
Thanks for the replies.