Reviews – Mindsensors MotorMux

After building my original DominoBotNXT I was not happy with the need for it to backup each time a domnio was placed. (see link for details on this). The stanard NXT system provides only 3 motor ports. On DominoBotNXT, 2 were used for the drive wheels and 1 for the domino placement gate. This resulted in the need to tied the domino conveyor that carries each domino to the gate to be driven directly from the left drive wheel. When placing a domino, the distance between each was too wide, so it would have to back up each time one was placed. To fix this, I needed a 4th motor and a means to drive one. So, how do you do this with only 3 motor ports you ask??? Good question, I’m glad you asked as that is what this page is for….

The Motor Multiplexer from Mindsensors attaches to a single sensor port and allows the NXT to drive an additional 4 motors. In my case, I only needed 1. Using RobotC, I was abled to write (with some help from Dick Swan and Nitin Patil – thx guys) code that would allow communication with the IC2 interface on the sensor to control the 4th motor. So, in the programming environment, I simply had another motor port and use it in a similar way to the 3 core ports on the NXT. It only took a little bit of code to get this working. Now, DominoBotNXT can continue to drive forward while placing domino’s – making it much faster at its task. For info and a video on this, visit my DominoBotNXT2 page.

I am happy with the way this sensor works. I was working with a pre-production beta version that had some glitches (one port did not work), but I have been assured that the production units have this addressed.

The sensor uses a standard NXT cable plug to interface the unit with the NXT. It is not encased in any plastic or bricks. Instead, it provides standard width Lego mounting holes to integrate with studded or studless beams and connectors.

Have a sensor or add-on that you want reviewed? Drop me a line.

DominoBotNXT w/MotorMux

This page is dedicated to the further enhancements that I have done to DominoBotNXT. For more info on the original DominoBotNXT, have a look here.

One of the drawbacks of the original was that due to the 3 motor limit, it had to backup to properly place dominos. This was because the domino-placing component was tied directly to the drive wheels. So, as it drove forward, a domino would make its way to being placed in the holder mechanism. Doing this caused the robot to move forward approx. 4 inches. Since this is too far for domino’s to actually cause any chain reaction, the robot had to move each newly placed domino back to be within 1″ of the last placed one.



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