Aims

• 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

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

Process

• 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

• Snubber circuit for solenoids

  • Something like http://jnf.indiansecurityproducts.info/downloads/Oct06_Vending%20mc.pdf

• RC snubber component/circuit with 0.1uF (approx 400V rating) and 150 Ohm resistance in parallel with the load should do
  • Need to test this on a breadboard before looking for a permanent way of implementing it

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