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Tuesday, December 21, 2010

LEGO robot lays dominoes not eggs - Hack a Day

LEGO robot lays dominoes not eggs

posted Jan 11th 2010 11:00am by Mike Szczys
filed under: robots hacks, toy hacks

[Mattias] brings the awesome once more with his LEGO robot that sets up dominoes. You’ll remember his work from the wooden keyboard case and the mechanical binary adder. This time around he’s still exercising those woodworking skills by making his own domino tiles, but it’s the robot that makes this interesting. In the must-see video after the break the device lays perfectly straight, perfectly spaced dominoes just begging to be upset by a spoiled toddler. The robot is nothing more than handful of LEGO parts powered by a tape deck motor. The parts may be meager, but there’s an abundance of ingenuity tied up in the design.

[Thanks Sion via The Awesomer]

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Lego domino row building machine

Way back in 1985, I built my original domino row building machine out of Lego. I thought it would be neat to have some video of it to post on YouTube, but of course, the original machine was long disassembled. So this gave me reason to pull out the old Lego again and build a new domino row building machine. The set at my parent's hadn't been played with since building the Lego marble machine in 1996!

The new machine is an improvement on the original one. Primarily, it's more compact. The first machine from way back was an experiment and I never went back to optimize it. With this machine I already knew that the concept worked so I focused on trying to make it as compact as possible.

The machine works by having a magazine of dominoes that is dragged along the table and a slider that moves back and forth sliding one domino out of the magazine at a time. All along, the machine is driving forward, which causes the released dominoes to be spaced out.

The key idea that makes the machine work is that the magazine is just a row of dominoes dragged along the table. This avoids the problem of having to somehow lower the dominoes onto the table. My first unsuccessful attempts back in 1985 involved dropping the dominoes out of the magazine onto the table. But the impact of dropping the dominoes would often cause them to tip over, with ruinous consequences.

I used an old tape deck motor for the drive. I'm powering it off of a long wire to a home made benchtop power supply. A Lego motor would have been more elegant but I didn't have one handy. All Lego motors have some built in reduction gearing, so the first belt and pulley would have been unnecessary.

The tape deck motor is fairly heavy, which helps give the machine enough traction. Putting the batteries on board the machine would have been a sensible thing to do, not just to add weight but also avoid the nuisance of having to worry about what the wire dragged by the machine might knock over. But I didn't have batteries or a battery holder handy.


Lego domino row building machine
LEGO robot lays dominoes not eggs - Hack a Day
Lego domino row building machine
Creating wooden enclosures - Hack a Day
Binary adder will give you slivers - Hack a Day
YouTube - Lego domino row building machine

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