"Chum Dispenser" solution with picaxe - advice needed by noob

hippy said:

I think it would help to produce a clear specification of what is needed and to start with it seems to split between two parts; the primary part which flings fish and a secondary part, an alarm which sounds when a fish hasn't been flung. We can deal with the first without worrying about the second, bolt that on later.

There is a three way switch, a speed pot and a motor. That motor is constant speed, only on or off, so no need for motor speed control; the speed pot controls the rate of delivery not the speed of motor.

Switch position 1: Motor stopped. Easy.

Switch position 2: Motor always on. Also easy.

Switch position 3: The more complicated part. Motor runs until a fish has been flung. Once flung the motor stops for a period set by the pot, then starts again. An additional requirement will probably be that it is responsive to pot changes; if set for a minute then switched to 10 seconds one does not want to wait for the rest of that minute to pass before it changes to a 10 second interval.

That gives us a basic framework for a single task, linear program which could be as follows -

Code:

MainLoop:
  Do
    Gosub DetermineSwitchPosition
    If switchPosition = 1 Then Stopped
    If switchPosition = 2 Then AlwaysOn
    If switchPosition = 3 Then IntervalTiming
  Loop

Stopped:
  Gosub TurnMotorOff
  Do
    Gosub DetermineSwitchPosition
    If switchPosition <> 1 Then MainLoop
  Loop
  
AlwaysOn:
  Gosub TurnMotorOn
  Do
    Gosub DetermineSwitchPosition
    If switchPosition <> 2 Then MainLoop
  Loop

IntervalTiming:
  fishFlung = 0
  Gosub TurnMotorOn
  Do
    Gosub DetermineSwitchPosition
    If switchPosition <> 3 Then MainLoop
  Loop Until fishFlung <> 0
  Gosub TurnMotorOff
  elapsedTime = 0
  Do
    Gosub DetermineSwitchPosition
    If switchPosition <> 3 Then MainLoop
    Pause 10
    elapsedTime = elapsedTime + 10
    Gosub DeterminePotTime
  Loop Until elapsedTime >= potTime    
  Goto IntervalTiming

TurnMotorOn:
  ; Some code here
  Return

TurnMotorOff
  ; Some code here
  Return

DetermineSwitchPosition:
  ; Some code here which sets 'switchPosition' variable
  Return

DeterminePotTime:
  ; Return potTime as 1000ms to 60000ms
  Symbol MAX_SECONDS = 60
  Symbol MIN_SECONDS = 1
  ReadAdc POT_PIN, potTime
  potTime = MAX_SECONDS - MIN_SECONDS * potTime / 255 + MIN_SECONDS * 1000
  Return

The one thing missing in that is there is nothing which sets the 'fishFlung' variable. An interrupt when the opto detector activates as a fish passes through the beam and sets 'fishFlung=1' will solve that.

To add an alarm one needs to add some elapsed timer counting when the motor is on and we are waiting for the fish to be flung, something like ...

Code:

IntervalTiming:
  fishFlung = 0
  [b]elapsedTime = 0[/b]
  Gosub TurnMotorOn
  Do
    Gosub DeterineSwitchPosition
    If switchPosition <> 3 Then MainLoop
    [b]Pause 10
    elapsedTime = elapsedTime + 10
    If elapsedTime >= 60000 Then SoundAlarm[/b]
  Loop Until fishFlung <> 0

All timing is done with millisecond units and 16-bit word variables hold time as millisecond values. That limits things to 65 seconds which is okay here.

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