Introduction: Servo Controlled Marble Maze

About: A Maker since childhood with all the classic symptoms, a robot builder, and an Internet software CTO/Tech Product Manager.

This is version of the classic marble maze (there are choices in the path), where the pan and tilt are controlled by hobby servos. With the servos, you can work the maze with an R/C controller or a PC etc.

We built this one to be used with TeleToyland, and you can try it out live at the TeleToyland Marble Maze, and a second bigger one, the TeleToyland Marble Maze 2.

To make setting up and changing the maze easy, we used a Lego plate and bricks.

This Instructable has an easier and nicer build of this Marble Maze.

Step 1: Materials

The materials for this one are pretty easy - should all be available at your local home store (except the servos).

Metal - for the following, we used about 5 feet of each:
1" wide x 1/8" thick aluminum bar for the X axis
1 1/2" wide 1/8" thick aluminum bar for the Y axis
1 1/2" wide by 1/16" Aluminum angle

1x4 pine for the base - need about 34"

#6 nuts/bolts - a few lengths, a couple 1" ones, and the rest 3/4 and 0.5 inches long
#6 washers and #6 split lock washers

We used Hitec HS-625MG servos. Even though the mechanism is well balanced, standard hobby servos tended to jitter a bit. Note that for TeleToyland, we also turn the servos off when they are not moving.

The right size marble for two Lego studs is 9/16" (14mm), which is common on board games. Land of Marbles has many colors and styles available in this size.

Step 2: X Axis

We are calling the inner ring the "X Axis".

We basically man-handled this together on the bench vise. If you have a bending brake, then we are envious :-)

The X axis needs to be the size of the Lego plate you will be using, so for the Lego Large Green Baseplate (item #626), it should be 10 inches x 10 inches. For the Lego X-Large Gray Baseplate (Item #628), it should be 15 inches by 15 inches. For the rest of this Instructable, we'll use the green baseplate measurements.

We cut the 1" aluminum bar it to length, then marked where the bends should go. Then we clamped the bar in a bench vise to bend it. Note the connection is in the middle of one side rather than the corner. This made sense to us since we get the extra thickness for the axle, and it seemed like it would be easier to join it on a side rather than a corner.

Once it was bent into shape, we used a smaller piece to join the ends, and used 4 #6 bolts to hold it with nuts and split lock washers.

In the middle where we used the small plate to join the ends, we placed a 1" #6 bolt pointing out of the ring. This will be the pivot for the X Axis.

On the opposite side, we placed a servo horn. We drilled a large hole to fit the plastic ridge around the center (on the other side of where the servo attaches), then used a couple #6 screws to mount the servo horn. the horn is mounted on the outside of the ring. The large hole in the center allows the servo set screw to be tightened from the inside.

Step 3: Y Axis

We are calling the middle ring the "Y Axis".

The width is the most critical dimension - needs to fit the X Axis with just enough clearance for the servo and for the axle. The length needs to leave enough clearance for the X Axis to move freely as it rotates. Ours is about 11 1/4 inches x 12 inches.

As with the X Axis, we used a small plate to join the YAxis, added an axle, and a servo horn.

The main difference is that we need to mount the servo that actuates the Z Axis, and we inset it at the point that centered the X Axis inside the Y Axis. Once we lined that up, we also drilled the hole for the X Axis axle/pivot to fit in to.

Step 4: The Maze

The outer ring just needs to hold the Y Axis servo and the pivot hole. We chose to use some 1 1/2 inch angle aluminum around it, but you could do this a lot of ways - now that we look at it, maybe even with just a wood frame and a couple brackets.

The construction was as before, though we needed to cut the angle aluminum to bend it at the corners (see picture). We used some 1x4 inch pine to get it off the ground.

Ours is about 14 1/2 inches x 13 1/2 inches. Again, the width is critical, and the length needed to allow for the X Axis servo to swing freely.

The Lego plate was taped on to the inner ring with some packing tape. For the bigger Marble Maze, we added two 1x3 inch boards across the X Axis to help support the Lego plate.

The marble size is key - we tried a few to find the right size, and even found some UV reactive ones.

Step 5: Comments

- There are several marble maze projects out there. Some use servos on the traditional game. We chose to do one without the holes to avoid building a ball return system

- RoboRealm did an automatic vision based solver for the 2008 Maker Faire.

- On the large one, we ended up adding some counterweights to keep it more balanced when being used.

- Check out this separate Instructable on how the Marble Maze was setup for local control at a show using just an Arduino and some push buttons.