This post is part of the Rack Box Project series.

Emergency stop controller for the rack box project. Uses two 555 timers.

Table of contents

Details

This module will cut the main power to the Rack box if emergency power off is activated. The module is powered by a separate 12V supply; the emergency supply.

Main fuses are located on the module front, a green LED shows that voltage is present. If one of the fuses should burn out Main monitoring unit will signal a supply error.

Two big red LEDs flash when the emergency power off is activated. An alarm output, used for a strobe, is also activated, but this can be disabled with a switch.

From the module front one can trigger and reset the emergency power off, this can also be done from the Rack status panel. Or with Serial I/O system, using the Digital emergency interface module.

The module uses two 555 timers, one makes the big red LEDs to flash when triggered. The other is used as a reset delay, requiring the reset button to be pressed for five seconds.

Layout sketch, with labels in Norwegian

Video

Quick demo showing the operation of the emergency power off controller. First triggering, then resetting the emergency power off.

At 2:00 the rack box emergency power off is triggered and everything shuts down — then reset.

D-Sub 9-pin

  1. 12v+ in
  2. 12v- in
  3. 12v+ out
  4. 12v- out
  5. Reset switch input
  6. Trigger emergency input
  7. Emergency relay output
  8. Emergency LED output
  9. Emergency strobe output

Photos

Emergency power off relay in the rack box
Module installed in the rack box (to the right)
LEDs and switches on the emergency power off controller
Emergency power off controller
Inside module
Inside module

Schematic drawing

Schematics for the emergency power off controller

Parts list

  • 2 × Capacitor, aluminium electrolytic, 47 µF, 25V
  • 2 × Capacitor, metallized polyester foil, 10 nF, (0.01 µF)
  • 1 × D-sub soldering cups, 9 pin male
  • 2 × DIL socket, 8-pin, 7.62mm
  • 2 × Diode, rectifier, 1 A, 400V, 1N4004
  • 2 × Diode, small signal, 1N4148/Ph
  • 1 × Enclosure, plastic (1591), 112x62x31mm
  • 2 × Fuse 5x20 mm, 2 A, fast-acting
  • 2 × Fuse holder, open, PCB, 5x20mm
  • 2 × Fuse holder, open, PCB, Protective cover
  • 2 × LED 10mm, Red, 2.0V, 20mA
  • 1 × LED 5mm coloured clear, Green, 2.1V, 20mA, 30mcd, 10°
  • 2 × LED 5mm, Red/Green, 2.0 2.1V, 10mA, 100 63mcd, 30°
  • 3 × LED holder 5mm, RTC51, black plastic
  • 2 × Mounting bracket, DIN rail, Plastic
  • 32 cm2 PCB, stripboard, 100x160mm, 160cm2
  • 2 × Relay, 2 CO, HJR1-2C, 12 VDC, 1A 120V, PCB
  • 4 × Resistor, carbon film, 0.25W, 4.7 kΩ, 5%
  • 1 × Resistor, carbon film, 0.25W, 100 kΩ, 5%
  • 5 × Resistor, metal film, 0.6W, 1 kΩ, 1%
  • 1 × Switch, push-button, 1-pole, 1A, 50VAC, off-(on)
  • 2 × Switch, toggle, 1-pole, micro, on-(on)
  • 1 × Switch, toggle, 1-pole, micro, on-on
  • 2 × Timer IC, NE 555, 0/+70 °C, DIL8
  • 2 × Transistor, NPN, 100 mA, 45V, 0.5W, BC547B

Last commit 2023-02-05, with message: Add series for the rack box project.

Rack Box Project series

  1. Parallel port I/O module
  2. Power supply and fuse monitoring module, AVR
  3. Monitored fuse box, 6 channels
  4. Stack lights and horn controller — with AVR
  5. Mute and light controller for the Rack box — AVR module
  6. Monitored fuse box, 4 channels
  7. Module heartbeat monitor, 6 inputs — AVR
  8. Controller for lights and relays — AVR driven
  9. Emergency power off controller — controlled by 555 timers
  10. Fan controller with LCD — AVR powered
  11. Sound alarm control unit — AVR module
  12. Multiplexer output extender
  13. Multi-purpose AVR module
  14. Electric heater and timer controller — AVR
  15. Module heartbeat monitor, 15 inputs — LCD and AVR
  16. Serial port I/O module with 11 inputs — AVR
  17. Serial port I/O module with 9 in and outputs — AVR
  18. Serial interface for emergency power off — AVR
  19. Status panel for the Rack box project
  20. Intruder alarm system controller — AVR
  21. Serial port I/O module with 15 inputs — AVR
  22. Serial interface module, with analog and digital I/O — AVR
  23. The rack box project — an overview