Simple alarm circuit to monitor up to eight inputs, from e.g. production equipment. If any inputs are triggered an alarm is sounded. Uses the AVR AT90S2313 microcontroller.

Table of contents

Details

This module was built for a production line at my previous workplace, its purpose was to serve as a single alarm system controller for an entire production line. It monitored up to eight machines, each with its own alarm timer. If an alarm was triggered; a one second signal was given with the horn. That input would then be muted, and not give any more alarm until the current alarm situation had been cleared for a minimum of seven seconds.

I/O

All inputs was electrically isolated from the production equipment with opto-isolator.

Inputs

  1. PB.0 Equipment #1 alarm signal (pin 12)
  2. PB.1 Equipment #2 alarm signal (pin 13)
  3. PB.2 Equipment #3 alarm signal (pin 14)
  4. PB.3 Equipment #4 alarm signal (pin 15)
  5. PB.4 Equipment #5 alarm signal (pin 16)
  6. PB.5 Equipment #6 alarm signal (pin 17)
  7. PB.6 Equipment #7 alarm signal (pin 18)
  8. PB.7 Equipment #8 alarm signal (pin 19)

Outputs

  1. PD.4 Siren/horn (pin 8)

Source code

Schematic drawing

Production stop alarm schematics

Parts list

  • 1 × AVR AT90S2313-10PI, DIL-20, 10 MHz, 15 I/Os
  • 1 × Capacitor, aluminium electrolytic, 10 µF, 25V
  • 2 × Capacitor, aluminium electrolytic, 47 µF, 25V
  • 2 × Capacitor, ceramic, 22 pF, 100V
  • 1 × Capacitor, ceramic, 1 nF, 100V
  • 1 × DIL socket, 20-pin, 7.62mm
  • 8 × Optocoupler, single, CNY17F-3, DIL-6
  • 64 cm2 PCB, stripboard, 100x160mm, 160cm2
  • 1 × Quartz crystal oscillator, 4 MHz
  • 8 × Resistor, carbon film, 0.25W, 330 Ω, 5%
  • 2 × Resistor, carbon film, 0.25W, 4.7 kΩ, 5%
  • 8 × Resistor, carbon film, 0.25W, 10 kΩ, 5%
  • 8 × Resistor, metal film, 0.6W, 2.2 kΩ, 1%
  • 1 × Switch, push-button, PCB, 1-pole, H4.3mm, vertical, black
  • 1 × Transistor, NPN, 100 mA, 45V, 0.5W, BC547B
  • 1 × Voltage regulator +5V, 2 A, L78S05CV