digital write HIGH/LOW does the opposite

Other Hardware Motors, Mechanics, Power and CNC
1

Hi All,

Hopefully an easy one... when my code writes HIGH, the motor turns off, when LOW is written in turns on, the opposite should happen (& I swear was happening before). The HIGH/LOW is supposed to be controlling the PNP transistor on/off.

Any ideas I can try to fix?

int ledPina=3;

void setup()
{
 pinMode(ledPina, OUTPUT);
}

void loop(){
    digitalWrite(ledPina, HIGH);
    delay(2500);    
    digitalWrite(ledPina, LOW);
    delay(5000);
   
}

Screen Shot 2017-02-25 at 11.48.48 PM.png
Screen Shot 2017-02-25 at 11.48.48 PM.png1032×1246 65.1 KB

2

You could post a schematic

3

Hi, If that's a PNP transistor then it's a "high side" switch, and the inverted operation is normal. Pulling the PNP base towards ground turns it on.

A schematic would make this clearer..

4

No fix needed, its functioning correctly. Perhaps your code would benefit from

#define ON LOW
#define OFF HIGH

to make things clearer.

5

Hi guys,

Thanks for the help, all working now. Yes, I hadn't understood how a PNP transistor works (my mistake).

& @MarkT, I input your code as the only change to get it working - now OFF = HIGH & the code is easy to follow & understand.

Thanks!