State Machine Controls Garage Door Over The Internet

January 10, 2019 by 11 Comments

Home automation has been a hot-button topic time and again since the dawn of the personal computer age. These days, thanks to modern communications technology, it’s possible to do some pretty cool stuff. [Brad Harbert] decided to automate his garage door, controlling it over the Internet.

The build relies on a Particle Photon to do the heavy lifting of connecting the door to the Internet. Particle offer a cloud service that makes setting up such a project easy for the first timer, and [Brad] was able to get things working quickly. A relay is used to activate the garage door remote button, as it was desired to leave the main control board of the garage door opener untouched. Reed switches are used to sense the position of the door, and [Brad] coded a state machine to ensure the door’s current state is always known.

It’s a simple project, but [Brad]’s use of state machine techniques and position sensing mean it’s less likely he’ll get home to find his garage open and his possessions missing. If you’re new to programming simple physical devices, you could take a page out of his logbook. Of course we’ve seen similar builds before, like this one from parts from the scrapbin.

State Your Intentions More Clearly With State Machines

April 6, 2018 by 18 Comments

To the uninitiated the words ‘State machine’ sound like something scarily big and complex. They aren’t (necessarily) and can be quite useful. In fact, state machines are no physical machines but a model of processes. They link the states a system can be in with allowed transitions. For example a media player when stopped can change to play or open another file. While playing, it can go to pause, stop, reverse, fast forward and so on. A state machine creates a map of all states and how they are connected. It is an abstract tool hat offers a graphical approach to organizing your code before actually programming.

In his video [Chris Guichet] uses a state machine to debounce a switch for a beginner friendly introduction of the concept. He then shows how to turn the hand drawn map to actual code, including a section on debugging state machines.

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The Collatz-O-Matic: A State Machine With Style!

October 10, 2016 by 2 Comments

If you have ever thought that working out a Collatz sequence by hand was alright but lacked buttons and lights, the Collatz-o-matic by [mechatronicsguy] has you covered!

collatz-o-matic-closeupThe device is a type of Tag system calculator. [mechatronicsguy] explains that a Tag system is a method of computing similar to a Turing machine; it consists of a read & write FIFO array (or tape or queue) of indeterminate length, and at every step the system reads the symbol at the “head”, deletes a fixed number of symbols from the “head”, and depending on what that first symbol was, appends one or more symbols to the “tail”. Then the process repeats with whatever new symbol is at the head.

The Collatz-o-Matic uses an RGB LED string to represent the queue, and is set up in the following way:

  1. Delete two symbols (tags) from the front of the queue.
  2. If the first symbol deleted was:
    1. A – then write BC to the rear of the queue
    2. B – then write A to the rear of the queue
    3. C – then write AAA to the rear of the queue

Numbers are as easily represented as any other symbol, and the Collatz conjecture is that no matter what integer you start with, the system (probably) always eventually reaches state 1. There is video of the device demonstrating exactly that embedded below. Continue reading “The Collatz-O-Matic: A State Machine With Style!” →

Object Oriented State Machine Operating System Goes Open Source

November 14, 2015 by 19 Comments

On a desktop computer, you think of an operating system as a big piece of complex software. For small systems (like an Arduino) you might want something a lot simpler. Object Oriented State Machine Operating System (OOSMOS) is a single-file and highly portable operating system, and it recently went open source.

OOSMOS has a unique approach because it is threadless, which makes it easy to use in memory constrained systems because there is no stack required for threads that don’t exist. The unit of execution is a C++ object (although you can use C) that contains a state machine.

You can read the API documentation online. Just remember that this is not an end user OS like Windows or Linux, but an operating environment for managing multiple tasks. You can, though, use OOSMOS under Windows or Linux as well as many other host systems.

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Embed With Elliot: Practical State Machines

September 4, 2015 by 41 Comments

Raindrops on roses, and whiskers on kittens. They’re ok, but state machines are absolutely on our short list of favorite things.

There are probably as many ways to implement a state machine as there are programmers. These range from the terribly complex, one-size-fits-all frameworks down to simply writing a single switch...case block. The frameworks end up being a little bit of a black box, especially if you’re just starting out, while the switch...case versions are very easy to grok, but they don’t really help you write clear, structured code.

In this extra-long edition of Embed with Elliot, we’ll try to bridge the middle ground, demonstrating a couple of state machines with an emphasis on practical coding. We’ll work through a couple of examples of the different ways that they can be implemented in code. Along the way, we’ll Goldilocks solution for a particular application I had, controlling a popcorn popper that had been hacked into a coffee roaster. Hope you enjoy.

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Becoming A State Machine Design Mastermind

August 13, 2015 by 23 Comments

Imagine a robot with an all-around bump sensor. The response to the bump sensor activating depends on the previous state of the robot. If it had been going forward, a bump will send it backwards and vice versa. This robot exhibits behavior that is easy to model as a state machine. That is, the outputs of the machine (motor drive) depend not only on the inputs (the bump sensor) but also on the current state of the machine (going forward or backward).

As state machines go, that’s not an especially complicated one. Many state machines have lots of states with complex conditions. For example, consider a phone switchboard. The reaction to a phone going off hook depends on the state of the line. If the state is ringing, picking up the phone makes a connection. If the state is idle, the phone gets a dial tone. The switchboard also has to have states for timeouts, connection failures, three way calling, and more.

If you master state machines your design and debug cycles will both move along faster. Part of this is understanding and part is knowing about the tools you can choose to use. I’ll cover both below.

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Using State Machines In Your Projects

May 27, 2014 by 21 Comments

arduino, 16 button keypad and LCD display

 

[Tony] has developed a method of using a state machine to validate keypad inputs. His method checks the commands character by character as they are entered in by a 16 button keypad. State machines are often used to break down complex problems into sequential tasks, making code development easier. While [Tony’s] example uses the keypad, Arduino Uno, and a character LCD, the theory can be applied to numerous projects, such as this Dahlander motor switch.

As you see, state machines can be very versatile. Stick around after the break as we take a look at [Tony’s] state machine and provide a brief explanation of how it all works.  Continue reading “Using State Machines In Your Projects” →