As soon as we started the day, things seemed to be going well.  At last our code and Bluetooth had decided to cooperate for Station One, and the chocolate dispenser consistently lowered and applied pressure for the given amount of time.  We were elated with our immediate success, and then proceeded onto the next station: our old nemesis, the Whipped Creamer.

Station Two has a nasty habit of running forever and ever, regardless of the code we write or the commands we give it.  We’d tried restarting the code from scratch, changing the Bluetooth messaging method, and swapping out motors.  However, today will be different, we’re sure of it!  Our first idea was to display all messages and in use mailboxes to the screen of the NXT, to see exactly where the error originated.  Immediately something seemed strange; while the NXT in Station Two was supposed to receive two messages (one signaling the bowl-bot’s arrival and another containing the amount of whipped cream to dispense), only one was being recognized at the station.  Even after messing around with the code and swapping mailboxes, the first message was still the only one being transmitted.  Rather than working against Bluetooth and its mystifying properties, we decided it would be better to conform to its will, and only use one message.  This proved to be quite easy, but even after this simple change the improvement was remarkable.  The second station worked!

Lastly on the docket was the sprinkles/cherry station.  This station suffered from the same problems as Station Two; it tended to try and dispense sprinkles forever.  Luckily for us, we left the cap on for any and all tests, but something had to be done.  Having recently discovered the nature of Bluetooth messages and their tendency to ignore anything that wasn’t the first transmission, we immediately tried to condense all three of our messages (arrival, sprinkle shakes, cherries) into one message.  Using some simple multiplication code and division/remainder functions, we accomplished this quite easily.

At this point we just had to give ourselves high fives and fist bumps all around.

We had gone from an absolute quagmire of Bluetooth and unresponsive robots to a fully functioning system in a matter of hours.  We even tried running with condiments (but no ice cream) and it was entirely successful.  Without ice cream in the bowl, unfortunately, the sprinkles proved to be bouncier than anticipated, and we knew we were going to have a mess on our hands very soon.

Only one problem still reared its ugly head: the cherry dispenser.  After initial construction we believed the device to work well enough for final use, but now we see that we need improvements.  With any more than one cherry loaded, the paddles simply smash the queued cherries, getting juice everywhere and jamming up the system.  We need to rework the whole apparatus for a more useable and consistent approach.

Right now we are working on a hopper type of loader that opens up temporarily to allow cherries through.  We used a water bottle top and a plastic square to contain the cherries, and rotated the square in order to let out cherries.

The problem right now is that there isn’t enough force above the cherries to force them downwards through the aperture.  We are working right now to remodel, trying to combine the paddle idea and the rotating plate idea into a waterwheel type of dispenser.  Hopefully the idea will work!

3:27 PM:

Once again we’ve decided to change our game plan.  We think a conveyor belt + hopper might work the best, as long as the conveyor belt can somehow grab cherries out of the hopper.  We might have to use a glue gun and attach prongs of some sort along the belt.

4:51 PM:

After many failed attempts, we finally have a cherry dispenser design that we are sure will work.  It combines all the best elements of our previous ideas: 1) it holds many cherries so we don’t have to manually load them so often; 2) it dispenses only one at a time–consistently; and 3) it looks cool.

Basically it involves a vertical tube of cherries with a round knob at the bottom.  But the knob is shaped like pac-man–when the triangular cutout is facing up (aka, into the bottom of the tube) one cherry will fall into it.  As the knob continues to rotate, the cherry will be dumped into the sundae.  Yes.  We are extremely hopeful that tomorrow will bring sundaes!!

Day 10 Conclusions:

  • Bluetooth life is finally good! After many trials and tribulations, we’ve finally created what we hope is a foolproof code.
  • Cherries are an obscure item that requires a dispensing mechanism different than almost anything in existence.  However, many existing systems can be combined to make a great, customized dispenser.

To-Do for Day 11:

  • Finish cherry dispenser.
  • Make sundaes.
  • YES.

One Response to “Day 10: So Close”

really great!! i think the cherry dispenser is how the m&m and other candy dispensers work….make sure to post a video of the sundae in action when you actually get ice cream and load up the bowl-bot.

June 27th, 2011