ATTiny85 pin pulling input down

i've got project breadboarded using attiny85. input attiny output pir sensor. i've tried couple of sensors of 2 types have. standalone, senors work expected i.e. few millivolts low , apprx. 3.7v high. when pir output connected physical pin 3 (ide pin 4) high output of pir pulled low approx. 68 millivolts. i've tried 3  attinys; results same. i've swapped 1 of sensors didn't work attiny 1 working in project using nano , works fine in nano project. jumpering attiny input pin 3 5v while pir still connected same pin results in project working if pir output did go high , reading on pin 3 approx. 4.7v. can't understand why attiny pin pullng down output of pir. ideas? - scotty  

code: [select]

int ldr_val = 0;
byte ldr_pin = a3;
byte led_pin = 2;
byte pir_pin = 4;
int ledpin[] = {
  0, 1,
};         // pwm pins only
int ledstate[2];               // last state of each led
long randnumber;
boolean sense_dark = false;
unsigned long sense_dark_start = 0;
boolean dark = false;
boolean pir_detect = false;




void setup() {
  pinmode (led_pin, output);
  pinmode (pir_pin, input);
  digitalwrite (led_pin, high);
  delay(500);
  digitalwrite (led_pin, low);
  delay(500);
  digitalwrite (led_pin, high);
  delay(500);
  digitalwrite (led_pin, low);
  delay(500);
  digitalwrite (led_pin, high);
  delay(500);
  digitalwrite (led_pin, low);
  delay(500);
  (int = 0; <= 2; i++) { // set each led pin output
    pinmode(ledpin[i], output);
  }
  randomseed(analogread(0));     // seed rnd generator noise unused pin
  (int = 0; <= 2; i++) { // init. each led random value
    ledstate[i] = random(20, 201);
  }
  // put setup code here, run once:
  //serial.begin(9600);
  //serial.begin(9600);
}

void loop() {
  dark_detect();
  report();
  pir_detect();
  illuminate();

  if (dark) {
    (int = 0; < 2; i++) {             // each led
      analogwrite(ledpin[i], ledstate[i]);     // set pwm value of pin determined previously
      randnumber = random(-40, 41);            // generate new random number , add current value
      ledstate[i] += randnumber;               // range can tweaked change intensity of flickering
      if (ledstate[i] > 200) {                 // clamp limits of pwm values remains within
        ledstate[i] = 200;                     // pleasing range pwm range
      }
      if (ledstate[i] < 10) {
        ledstate[i] = 10;
      }
    }
    delay(100);    // delay between changes
  }
  else {
    analogwrite(ledpin[0], 0);
    analogwrite(ledpin[1], 0);
  }
}

void dark_detect() {
  ldr_val = analogread(ldr_pin);
  if (ldr_val < 450) {
    if (sense_dark == false) {
      sense_dark_start = millis();
    }
    sense_dark = true;
  }
  else {
    sense_dark = false;
    sense_dark_start = 0;
  }
  if (sense_dark & ((millis() - sense_dark_start) > 10000)) {
    dark = true;
    //digitalwrite (led_pin, dark);
  }
  else {
    dark = false;
    //digitalwrite (led_pin, dark);
  }

}

void illuminate() {
  if (dark && pir_detect) {
    digitalwrite(led_pin, high);
  }
  else {
    digitalwrite(led_pin, low);
  }
}

void pir_detect() {
  pir_detect = digitalread (pir_pin);
  //digitalwrite (led_pin, pir_detect);
}

void report(){
  //serial.print("pot value = ");
 //serial.println(pot_val);
 
  //serial.print("dark adjustment = ");
 //serial.println(dark_adjustment);
 
 //serial.print("ldr value = ");
 //serial.println(ldr_val);
 
 //serial.print("sense dark start = ");
//serial.println(sense_dark_start);

//serial.print("sense dark= ");
//serial.println(sense_dark);

//serial.print("                                           dark= ");
//serial.println(dark);
 
 //serial.print("millis = ");
 //serial.println (millis());
}


try using

code: [select]

pinmode (pir_pin, input_pullup);

or use external 1k - 10k pullup resistor if stronger signal needed



https://learn.adafruit.com/pir-passive-infrared-proximity-motion-sensor/connecting-to-a-pir

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