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ATTINY85 ALARM (Custom PCB protoboard Alarm)

Developed by C.A Torino, TECHRAD Radical Technology

Links to TECHRAD ZA.

Setup

A simple Attiny85 alarm system with a siren, buzzer and a magnetic reed switch. The system has reverse voltage and a battery protection circuit. Below is the simple but effective firmware code:

Compiled and updated in the Arduino IDE.

/************************************
 * ATTINY85 PIR+REED SWITCH ALARM
 * C.A TORINO 31/10/2020
 * V1.3
*************************************/

#define keyswitch 3
#define reedswitch 4
#define led 2
#define alarmsiren 1
#define buzzer 0

int reed;
int key;

void setup() 
{
  pinMode(reedswitch, INPUT);
  pinMode(keyswitch, INPUT);
  pinMode(buzzer, OUTPUT);
  pinMode(led, OUTPUT);
  pinMode(alarmsiren, OUTPUT);
  digitalWrite(alarmsiren,LOW);
  digitalWrite(led, LOW);
  digitalWrite(buzzer, LOW);
  Startup();

}

void Startup() 
{  
for (int j=1; j<=10; j=j+1) 
{
      digitalWrite(led, HIGH);
      digitalWrite(buzzer, HIGH);
      delay(1000);
      digitalWrite(led, LOW );
      digitalWrite(buzzer, LOW);
      delay(1000);
}
      digitalWrite(buzzer, HIGH);
      delay(250);
      digitalWrite(buzzer, LOW);
      delay(250);
      digitalWrite(buzzer, HIGH);
      delay(250);
      digitalWrite(buzzer, LOW);
      delay(250);
}

void loop() {
 reed=digitalRead(reedswitch);
 key=digitalRead(keyswitch);
  
 //high reed
 if(reed==HIGH){
   if(key==HIGH)
   { 
    digitalWrite(led, HIGH);
    digitalWrite(alarmsiren,LOW);
    } 
   if(key==LOW){;}
   digitalWrite(led, LOW);
   digitalWrite(alarmsiren, LOW);
   }
 //low reed
 if(reed==LOW){
   if(key==HIGH)
   {
    digitalWrite(led, HIGH);
    digitalWrite(alarmsiren,LOW);
    }
   if(key==LOW)
   {
    digitalWrite(alarmsiren, HIGH);
    digitalWrite(led, LOW);
    delay(60000);
    digitalWrite(alarmsiren, LOW);
    }
   }
}

1. Full board

2. Reverse voltage protection circuit components

3. Low voltage battery cut-off circuit components

4. 5v DC regulator circuit components

Development History

Version v1.4.0 (01-November-2020)

Bugs

Siren sound to soft when activated via 2N2222A transistor switching GDN
Solution Resistor issue. remove 1K resistor between Attiny85 pin and transistor.
2N2222A transistor is getting too hot. Look for alternative high current transistor.

Version v1.3.0 (31-October-2020)

Firmware improved led changed to green led with 1K resistor. Notification buzzer added.

PCB Design as follows:
- Reverse voltage circuit.
- low voltage protection circuit.
- 5v regulated circuit.
- Attiny85 + transistor + buzzer + siren circuit.

PCB soldered and tested. 2 prototypes made and both work effectively.

Version v1.2 (30-October-2020)

Breadbord testing of Attiny85 and A2N2222A NPN switching transistor.

Firmware version 1.0 and 1.2 used and improved
Holes drilled into PCB for large 1N5822 Schottky Diode.
PCB divided into 2 since the components take up a lot less space.

Initial version v1.0 (28-October-2020)

Schematic for reverse voltage and battery low voltage acquired. Reasearch on components.

Useful links