Sunday, October 11, 2009


Here are some pictures and information about the DominoBot.

DominoBot lays dominoes in a pattern to spell out a message. The basic premise is the same as a very very slow dot matix printer.

DominoBot uses one NXT, two servos to drive, one servo to open and close the gate, and eight medium PF motors controlled with the HiTechnic IRLink to push dominoes out of the magazine. The code is written in RobotC and the pattern and array are created in MS Excel.

Inspiration for this project, as I mentioned was Chalkbot. I considered several different mediums to spell out the message including spray paint, bricks, water and finger paint. I chose dominoes because I have two very large sets of dominoes (272 dominoes total), and it would be easy to pick up and reload.

The robot weighs over 25 lbs., so I had to carefully build the structure and drive train to be able to support that much weight. It will only work on level, flat surfaces. I once pulled it across the table and broke a gear, so when I move it I have to completely pick it up and place it, even very small distances.

DominoBot needed to be able steer and the wheels have to be extremely robust. I devised two pivoting trucks with four wheels each connected by a differential gear. The differential gear allowed a very wide base for each driving motor while still allowing it to turn.

The PF motors are used basically the same way a pneumatic cylinder would be used. I cycle the motors forward for 1.5 seconds to push out a domino and reverse for 1.5 seconds to retract the pusher. A clutch gear is used to “bottom out” the pusher on both movements, so a cycle actually takes less than 1.5 seconds.

The gate at the domino exit chute is an afterthought. I found that when the dominoes slide out, they tended to slide four to eight inches and made the message incomprehensible. The gate stops them at the bottom of the chute and releases them at the same time.

I used MS Excel to create the pattern. This worked great because I could size and fill in the cells to see exactly what the pattern would look like. Then I used a couple of Excel formulas and created the actual code that I could copy and paste over to my RobotC program.

Each magazine slot can hold 32 dominoes, which allows for about 10-12 characters to be created. The message programmed right now is “LEGO RULES.” Originally I made the magazine so that it would be filled from the top, then I figured out that it would be much easier to fill from the back.


  1. very cool, my first reaction was oh well another dominobot! oh no i was wrong this is a domino printer bot !wow! and based on your design it would appear to be pretty quick at it too... how long did LEGO RULES take ? 9min?

  2. Nine minutes is a good guess and probably pretty close, but I didn't actually time it. It's not fast because it is so heavy and I had to really gear the motors down to handle the weight.

    I just finished shooting some video. I just need to edit it and put it out, which may take a day or two.