Multiplo Open Source Robots Arrive
When I heard that Multiplo planned to release an open source robots kit I was very excited by the possibilities. I was excited because for once, anyone with an interest in robotics would have access to the tools they need to get involved. Most existing robotics kits use proprietary parts and the user can’t add new parts they designed. With open access to all the design files, builders can custom-make their own components or modify an existing design to fit their needs.
Another reason I was excited was because the Multiplo robots use Minibloq Graphical programming Environment for Arduino. Minibloq allows the user to use the Duinobot, Arduino compatible Brain without knowing how to write code.
What’s in the box?
Multiplo Robots (http://multiplo.org) come in 3 different levels, starter kit, building kit and Monster kit. Each kit has roughly double the amount of equipment supplied. I used the builders kit.
The Multiplo Builders kit comes in a plastic tackle box with two fold out trays. Each compartment of the tray is filled with goodies. My kit included two geared DC Motors, Duinobot controller, 2 r/c servos, infrared remote, five different kinds of sensors, cables, wheels and lots of building blocks and hardware. There is enough equipment to build a fairly complex robot.
Building with Multiplo
Building with the Multiplo robot system is very fast and easy. Making things with Multiplo is not like making things with Lego, it’s more like making things with an erector set. There are a series of plastic pop rivets (PPR) to hold the building blocks together. Each building block has a series of holes evenly spaced 9mm apart on them. You insert the plastic pop rivets through the holes and then push down on the head of the PPR to close them. By combining aluminum brackets with the plastic building blocks and PPRs you are able to create a variety of platforms. If you make a mistake just flip that part over and pushed downward on the PPR to open it up again. The PPR are reusable and quickly replaceable. The PPRs are color coded for size and ease of identification.
Building with the Multiplo systems is not hard, but it does take attention to detail. You have to pay attention to where you place the plastic pop rivets in relation to the aluminum brackets and other components. If you make a mistake it’s very easy and quick to disassemble and correct your errors.
ROBOT PROJECT ASSEMBLY GUIDES
There are several robot project assembly guides available online. These projects include detailed drawings and pictures that show each step of the construction. Detailed drawings shows how to assemble the building blocks. The drawings show a red dot wherever a plastic pop rivets goes. The assembly drawings are color coded to show you which length of PPR to use.
When you use the assembly guides, use the drawing on the left side to see where to insert the plastic pop rivets into the bottom of the building block. Then place the second building block over the first one using the red dots on the right hand drawing to tell you how to align it. The drawings on the right side are for one side of the vehicle. Everything on the left side is for the other side of the vehicle. This could be confusing at first because there is no text in the instructions.
WHAT TO BUILD?
I decided to build the Three Wheeled Robot project to become familiar with the Multiplo system. I followed the instructions on the included CD but you should check the website for the latest updates before you get started.
There are several online robot building guides to choose from. You can use the designs as the basis for your own design work or simply build them as designed. I wanted to quickly become familiar with the building process so I just used one of the existing designs.
I began to mount components to the plastic building blocks using the plastic pop rivets, metal brackets and metric screws. Small components quickly build into larger assemblies.
One really neat feature of this robot is the flip top battery pack. I constructed a little arm from some brackets and building blocks. The arm pivots in a hole in the side of a building block. It makes maintenance of the batteries and Brain convenient.
The kit included two planetary gear drives attached to 12 V DC motors. The two motors are used to propel the robot across the floor and for steering. The motors attach to the included knobby tires and hubs (similar to an off-road R/C car tire). The wheel hubs are little complicated to build but work well.
Building the gripper claw is probably the most complex part of the build and the one that takes the most attention to detail. I found that I had to disassemble the parts a couple of times to get the assembly right. I didn’t look closely enough at the picture so I missed some things that weren’t evident like flat washer and lock washers in certain assemblies. I eventually got it right.
TIPS FOR BUILDING THE CLAW
• The Claw gear box uses three aluminum standoffs, a 40 mm screw, washers and a wheel collar to hold it in place. Also the secondary gear is not centered in gear box rectangle.
• Another thing I missed while building the gripper claw was that you need to stack two gears together to make the free-floating side of the claw. If you don’t use two gears then things won’t line up correctly.
• When you make the claw arm use the black plastic pop rivets instead of the gray ones. They will close better. I also used the black PPRs to mount the claw arm to the sides of the chassis. The gray ones are not quite long enough to make it easy to mount. Another thing to watch out for is when you’re mounting the steel rods for the gripper claw. It’s easier to slide the entire bar through all the holes with the appropriate wheel collars in place. If you try to spread the arms out to fit over the chassis sides it just doesn’t work very easily.
• When you mount the pressure sensors and sonar, it’s a good idea to plug in the cables before you bolted them to the building blocks.
RUNNING OF THE BOTS
Once I finished the 3 wheeled bot it was time to program it. Or was it? You see the Multiplo Builders kit comes with a pre-programmed Duinobot brain. All I had to do was install all the cables to the correct ports, put batteries in the Remote control unit and begin.
The program loaded on the Duinobot will not control the claw unit but it will control the e motors and steer the robot around. If you want to control the claw you can download a program from the forum to do it or write your own program.
Steering the robot is done with the numeric keypad of the remote. To go forward, press the 2 button. To go backwards, press the 8 button. Pressing the 4 and 5 buttons will make the bot rotate left or right. To stop, just press 5. Within minutes anyone can learn to steer this robot.
Multiplo delivered on their promise to bring an Open Source Robot building system to the market. The system is well thought out and well executed. The one area that could use some more attention is the documentation. There needs to be a step by step guide for the absolute beginner. Once this is created the Multiplo system could take on any comers.
If you would like to know more about the Multiplo building system, go to http://multiplo.org/ If you would like to download a free copy of the Minibloq Graphical Programming Environment, or sign up for the Minibloq updates newsletter.
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