Digital output extender with multiplexer

From uCtrl
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.
4EXM installed in the Rack box

Information

4EXM gives four extra outputs to the Parallel I/O module. Only one output can be active at any time, this means that 4EXM can only send signal pulses. The module contains a multiplexer and three pull-up resistors. The output is synced by the multiplexer. Green LED shows system in standby, while the blue LED is server time-out alarm. 4EXM quite simple takes three inputs and divides it binary, and out you get eight outputs. Since one output is active while all the inputs are low this is used for the standby LED. Totally we gain an extra four outputs.

Binary values

4EXM Parallel 1 Parallel 2 Parallel 3 Binary value
1 32 0 0 32
2 0 64 0 64
3 32 64 0 96
4 0 0 128 128
5 32 0 128 160
6 0 64 128 192
7 32 64 128 224

D-Sub 15-pin

  1. 0V
  2. 5V
  3. Input 1
  4. Input 2
  5. Input 3
  6. Output 1
  7. Output 2
  8. Output 3
  9. N/A
  10. Server time-out alarm LED (Main monitoring unit)
  11. Status-LED +
  12. Output 7
  13. Output 6
  14. Output 5
  15. Output 4

Images

Parts list

Qty. Part
1 D-Sub soldering cups, 15 pin male
1 Demultiplexer, 3 -> 8, 74HC138
1 DIL socket, 16-pin, 7.62mm
1 Enclosure, plastic (1551), 50x50x20mm
1 LED 5mm clear, Blue, 4.9V, 20mA, 350mcd, 12°
1 LED 5mm coloured clear, Green, 2.1V, 20mA, 30mcd, 10°
1 LED holder 5mm, RTC51, black plastic
1 LED lens 5mm, CLF 280, Blue
5 Resistor, carbon film, 0.25W, 330 Ω, 5%
3 Resistor, carbon film, 0.25W, 10 kΩ, 5%