求助各位大佬我想用4个npn晶体管改变电流方向

代码图片链接如下，请问我怎么改才可以通过这四个能起到改变电流方向的目的，虽然我也想用h桥:(
int temp = 0;
int Tempstatus;
int right=3;
int left=2;
float voltage;
float TempCelcius;
void setup ()
{
  Serial.begin(9600);
    pinMode (temp,INPUT);
  pinMode (right,OUTPUT);
  pinMode (left,OUTPUT);
}
void loop ()
{
  Tempstatus = analogRead (temp);//Math functions to converse analog signal to voltage signal
  voltage = (Tempstatus/1023.0)*5.0;
  TempCelcius = (voltage-0.5)*100.0;
  if  (TempCelcius >= 10 && TempCelcius <40)
  {digitalWrite(3,LOW);
   digitalWrite(2,LOW);
  }
  if (TempCelcius >= 41 && TempCelcius <=49)
  {digitalWrite(3,LOW);
   digitalWrite(2,LOW);
  }
  if(TempCelcius >= 50)
  {digitalWrite(3,LOW);
   digitalWrite(2,HIGH);
  }
   if (TempCelcius < 10)
  {digitalWrite(3,HIGH);
   digitalWrite(2,LOW);
  }
}

https://www.tinkercad.com/things/3IixNxH9IzG-surprising-jaagub-habbi/editel?sharecode=O9vJ7ZEk-tq1WB35KuQ_Zosx4q6UO-S0ahi5dae2UoA

呃，不知道