• redo all internal wiring and logic, except the refrigeration parts
  • make the machine more safe by doing things properly and reducing the voltage of exposed components
  • keep the software interface as simple or more simple than before
  • make the buttons on the front of the machine work for dispense
  • make it extensible so things can be added on
  • give the machine a general service where necessary (seals, rust protection, oil)

Draft Bill of Materials





Unit Cost


7 (./)


front button switches, 2.21N



20 (./)


each slot has double microswitches, there are 10 slots, 0.15N



7 (./)

5mm round white LED's

replace empty slot globes

Standard 5mm LEDs, White? Or red for empty, green for non-empty?





empty slot LED protection

< $0.05


stripboard or veroboard

mount LED resistors

10 (./)

4 pin connectors

one for each slot actuator unit

Molex mini-fit jr series 4way connectors Also compatible


1 (./)

9 pin connector

interface with distribution box

recycle old connector


1 (./)

manual drop button

reuse old button new button bought from altronics

1 (./)



FMD88-10 starter kit, i-STK88-10, (including , software, data cable)

$475 kit

1 (./)

PLC expansion card

additional IO



1 (./)


kinda need a power supply


1 (./)


led power and future expansion power

INA Solutions



42m (./)

4 core wire, 1mm minimum diameter (to carry 2A), 18AWG

actuator and empty switch wiring



11m (./)

9 core wire

front buttons and lights wiring



5m (./)

2 core wire

refrigeration fan power




reuseable cable ties


10m (./)

cable loom

cable loom for fans and actuators




terminal blocks

Altronics (see below)

3 (./)

galvanising paint

recoating everything

Dy-Mark Zinc Gal from Bunnings



1 (./)

pack 100 female quick connectors 4.8mm

attach to microswitches



1 (./)

pack 100 bullet male connectors

cable loom



1 (./)

pack 100 bullet female connectors

cable loom



1 (./)

pack 100 terminal pin connectors

terminal block



1 (./)

pack 10 male quick connectors 4.8mm

fridge fans



3 (./)

Fans to replace refrigeration fans

24V Altronics



3 (./)

Finger guards

base refrigeration fan covers



12 (./)

sheet metal screws

attach fans to cooler cover

60 (./)

2mm spacers (washers?)

otherwise fans will jam on lip of cover

1 (./)

electrical tape (white)



1 (./)


put in corners so water can't sit there and cause rust


Internal PLC IO Requirements

  • 10x24V DC input for can sensing
  • 7x24V DC input for front door buttons
  • 1x24V DC input for manual dispense mode button
  • 10x110V AC relay outputs
  • 7x 5V DC outputs for empty slot display


  • empty the machine and bring it into the clubroom. This means everything won't have to be packed up at the end of the day while we're working on it
  • remove one of the stacks and test a slot actuator to see what it runs off. This determines what hardware we use to drive everything, so we need to know.
  • purchase all required hardware (PLC, wiring, connectors, switches, etc.)
  • write software (state machine based programming implemented in ladder logic, should be quite trivial)

  • wire up on the bench and test
  • service the machine. A can of zinc spraypaint wouldn't go astray on some of the rust spots I think. Check all the seals. Oil what needs oiling. Clean what needs cleaning.
  • install everything into the machine and test

Wiring it up

  • Terminal Blocks
    • Earth (green/yellow) doubles as end clamp
    • End cap
    • 3 red - 24V power distribution positive (bridged)
    • 3 black - 24V power distribution ground (bridged)
    • Partition
    • 10 red - slot microswitches positive
    • 10 black - slot microswitch ground (bridged)
    • Partition
    • 10 grey - solenoid active
    • 10 blue - solenoid neutral (bridged)
    • Partition
    • 4 grey - 110V power distribution active (bridged)
    • 4 blue - 100V power distribution neutral (bridged)
    • 2 earth (green/yellow) doubles as end clamp
  • Commoning bars/shorting links (come in strips of ten that you can cut to length)
    • 8 (7 plus one spare)
  • Din rail
    • 2m
  • Slotted duct 3 metres

Total Order:

  • 13 red
  • 13 black
  • 14 grey
  • 14 blue
  • 3 green/yellow
  • 2 end caps
  • 2 end clamps
  • 4 partitions
  • 8 shorting links (2 of each colour)
  • 2m din rail
  • 1 Label set numbers 1 to 50
  • Network cable connection
    • Panduit CFPHS2IW Faceplate or similar
    • Panduit Cat 6 Mech and cable

Measured things

  • Can drop process: 400ms on, 500ms off, 660ms on, 300VAC peak-to-peak, 1.8A
  • Wire lengths:
    • Actuator units 0,1,2,3: 80cm actuator to wire harness, 210cm harness to corner of machine door, 40cm up door, 45cm across, 40cm up to terminal block (4-core minimum) (16.6m)
    • Actuator units 4,5: 80cm actuator to wire harness, 170cm harness to corner of machine door, 40cm up door, 45cm across, 40cm up to terminal block (4-core minimum) (7.5m)
    • Actuator units 6,7,8,9: 80cm actuator to wire harness, 140cm harness to corner of machine door, 40cm up door, 45cm across, 40cm up to terminal block (4-core minimum) (13.8m)
    • Buttons: 75cm across front of door, 60cm down edge of door, 45cm across, 40cm up to terminal block (8-core minimum) (2.2m)
    • Lights: 75cm across front of door, 60cm down edge of door, 45cm across, 40cm up to terminal block (8-core minimum) (2.2m)
  • The fans suck air through the fridge unit, they don't blow it
  • Plug coming from the back of the distrubution box (red 9 way):
    • Brown/White 110V
    • Blue/White Neutral
    • Red/White 100V

Extra Things To Consider

Stuff to fix in future

  • The 5x1mm washers acting as spacers for the bottom refigeration fans should be replaced with a 5mm spacer or piece of pipe instead - the washers will be impossible to put back on if the fans ever need to be removed
  • small can support Done! A small bracket has been made which can fit on any of the front slots. Ask BobAdamson how to use it.

  • coin return magic
  • coin counter
  • more LEDs, not blue
  • redo fan wiring (again)
  • front perspex lights
  • screens
  • button screens
  • snack machine keypad, 3 key needs more debouncing Sortof done. BobAdamson pulled it apart and cleaned the contacts. It could probably do with some small capacitors across each button if it keeps happening.

  • documentation and all code up-to-date in ~coke