Garage Gateway Controller FSM

Discussion in 'Homework Help' started by fiendslyr, Apr 13, 2011.

  1. fiendslyr

    Thread Starter New Member

    Mar 22, 2011
    Alright, so I have a homework problem I am working on. Here is the description:
    Construct a garage gateway controller implemented as a Finite State Machine (FSM). The gateway system
    (Figure 1) has the following features.
    • An electric motor (M) that allows the gateway to be moved upwards or downwards. The FSM has to
    generate the control signals (M1 and M2) to indicate when there should be motion and in which
    direction. These would correspond to actuator signals in a real system.
    • Two sensors that indicate if the gateway is in the topmost (ST) or bottommost (SB) position, respectively.
    • A switch (S) for users to open (close) the gateway when it is fully closed (open). For simplicity, once the
    gateway is moving (up or down) it cannot be stopped or the direction of the movement reversed until
    the corresponding sensor (SB or ST, respectively) is activated.

    So in a nutshell, I have no idea where to start with this. I just need help designing a FSM diagram and from there I know how to build it. I know there will intermediate states that the machine will go to from Topmost to Bottom most and vice versa. If someone can help me get started, I would really appreciate it.

    Edit: Here is the figure
    Last edited: Apr 13, 2011
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    Try constructing a flow chart. Actually two - one from open to closed, and the other from closed to open.
  3. fiendslyr

    Thread Starter New Member

    Mar 22, 2011
    Ok, so if i make a flow chart for lets say closed to open... How would I know how many states it would go through? So if I start at close, the bottom sensor will read "1" then do I just go to halfway open, then all the way open? Or a third of the way open and so on? I don't really understand how the intermediate states work (between close and open).
  4. Georacer


    Nov 25, 2009
    Consider the following:

    I think that you must build one and only one state diagram.
    You have 3 inputs (user button, ST and SB) and at least 2 FFs, so you 're looking at a 5 input state table. That's to know what you 're looking at.

    As for the intermediate states, I suggest making a "moving up waiting for ST" state and a "moving down and waiting for SB" state.
    Take a look here for a quick FSM tutorial:

    At any rate, post your work and we 'll talk more then.
  5. fiendslyr

    Thread Starter New Member

    Mar 22, 2011
    I've got a state diagram table (I went to my TAs office hours to get some help). So at this point, I don't think I need anymore help. Thanks for your initial help guys!