Fuse box with 4 monitored channels

From uCtrl
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This module was part of the rack box project — which was terminated when I moved out of my first apartment.
FB2 installed in the Rack box


FB1 has three 12V and 5V circuits, every circuit has fuses on both polarities and is monitored. Every pair of fuses supplies a optoisolator with positive and negative voltage. When both polarities are present the optoisolator will trigger the inverter. When the input of the inverter is triggered, the output will be inactive. If a fuse should break the optoisolator will cut the signal to the inverter, causing the output to be activated and a LED indicates which circuit is broken. All inverter outputs is connected to a OR gates that sends an alarm signal to Main monitoring unit. FB2 also monitors and external fuse.

D-Sub 25-pin

  1. 5V fuse 1 +
  2. 5V fuse 1 -
  3. 5V fuse 2 +
  4. 5V fuse 2 -
  5. 5V fuse 3 +
  6. 5V fuse 3 -
  7. 5V fuse 4 +
  8. 5V fuse 4 -
  9. From LED power supply
  10. Alarm signal to Main monitoring unit
  11. Signal from external fuse


Schematic drawing


Parts list

Qty. Part
1 Capacitor, aluminium electrolytic, 10 µF, 25V
1 Capacitor, ceramic, 1 nF, 100V
1 D-Sub soldering cups, 25 pin female
2 DIL socket, 16-pin, 7.62mm
1 DIL socket, 6-pin, 7.62mm
8 Diode, rectifier, 1 A, 400V, 1N4004
5 Diode, small signal, 1N4148/Ph
1 Enclosure, plastic (1591), 120x80x59mm
1 Fuse 5x20 mm, 315 mA, time-delay
9 Fuse holder, open, PCB, 5x20mm
8 Fuse holder, open, PCB, Protective cover
1 Hex inverter buffer, 4049, 6 channels, DIL16
1 LED 5mm coloured clear, Green, 2.1V, 20mA, 30mcd, 10°
1 LED 5mm, Orange, 2.0V, 20mA
1 LED 5mm, Red, 2.0V, 20mA
4 LED 5mm, Yellow, 2.0V, 25mA
2 Mounting bracket, DIN rail, Plastic
1 Optocoupler, 4-channels, PC817
1 Optocoupler, single, CNY17F-3, DIL-6
32 cm2 PCB, stripboard, 100x160mm, 160cm2
15 Resistor, carbon film, 0.25W, 330 Ω, 5%
5 Resistor, carbon film, 0.25W, 4.7 kΩ, 5%
6 Resistor, carbon film, 0.25W, 10 kΩ, 5%
2 Resistor, metal film, 0.6W, 1 kΩ, 1%
2 Terminal block, screw, 2.5 mm
5 Transistor, NPN, 100 mA, 45V, 0.5W, BC547B