Serial interface module for emergency power off

This page is kept for historical interest. It may document projects or methods that are obsolete and/or no longer relevant. The information here is not kept up-to-date.

This module was part of the rack box project — which was terminated when I moved out of my first apartment.

DEIM installed in the Rack status panel

RS232 interface module, with voltage measurement. Used to communicate with emergency stop unit in the Rack box project. Installed inside Rack status panel. Uses an AVR ATmega8 microcontroller.

Details

With DEIM it's possible to trigger and reset the emergency shutdown from Serial Client, the voltage on the 12V emergency supply is also measured and shown in Serial Client. The module also registers if the emergency shutdown is triggered and gives the option of disabling the emergency strobe. DEIM has three LEDs and one two way switch on the Rack status panel, a yellow LED flashes when there is serial activity. Two LEDs are dual colored (green/red), the color can be controlled from the computer. The switch can be set up using triggers in Serial Server.

Commands

• Inputs
  1. Value from emergency supply 12V
  2. Emergency shutdown status
  3. Status on switch 1
  4. Status on switch 2
• Outputs
  1. Trigger emergency shutdown (1 sec auto off)
  2. Reset emergency shutdown (10 sec auto off)
  3. Deactivate strobe (on/off)
  4. LED 1
     • 0 Off
     • 1 Green
     • 2 Red
  5. LED 2
     • 0 Off
     • 1 Green
     • 2 Red

I/O

Inputs

1. PC0 - Emergency supply 12V voltage for volt meter
2. PC1 - Emergency shutdown active (Emergency shutdown unit)
3. PC2 - Switch 1
4. PC3 - Switch 2

Calculations

Voltage

$(ADC\cdot 5)\cdot 0.006\approx V\pm 0.03$

Outputs

1. PB0 - Trigger emergency shutdown (Emergency shutdown unit)
2. PB1 - Reset emergency shutdown (Emergency shutdown unit)
3. PB2 - Deactivate strobe
4. PB3 - LED 1 Green
5. PB4 - LED 1 Red
6. PB5 - LED 2 Green
7. PD6 - LED 2 Red
8. PD7 - Activity LED
9. PD5 - Lifesignal (to Module stability monitoring unit 2) (optoisolator)

D-Sub connector

See Rack status panel for D-Sub connector.

Communication

Interfacing is done with RS-232, using MAX232 or MAX202.

Serial settings

Baud

9600

Data bits

8

Parity

None

Stop bits

1

Start command

*

Module ID

004

Source code

Bascom-AVR source is available in a git repository:
https://github.com/thomasjsn/AVR-Emergency-serial-interface-module

Gallery

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  DEIM

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  DEIM

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  DEIM

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  DEIM

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  DEIM installed in the Rack status panel

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Schematic drawing