Author Archives: Darkstar

3D Printers – The Home Inventors New Best Tool

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Late in 2009 a friend at work told me about a new kit that they bought on-line. It was called a Makerbot cupcake and it was a 3D printer. “What?” I asked, “Do you mean like the very expensive ones we have here at work that cost over half a million dollars?”. My work has for a long time had an Objet 3D printer which we use to create prototypes at work to test our mechanical design before creating production tooling (a ‘tool‘ is a machined steel block used to create plastic parts via the manufacturing process of Injection Moulding). The Objet machine is one of the main reasons the lead time of development projects has shortened as you can see, feel and review a computer design before you spend large amounts of money in creating physical parts.

From that conversation onward I was hooked. The possibility that I could create my own design parts at home just by printing them out was amazing. So I got on-line and began looking for 3D printers. At the time Makerbot was just up to their latest prototype version which I then bought. Several months and many hours of assembly and trouble shooting later I was the proud owner of my own Thing-O-Matic.

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Thing-O-Matic

My 3D printer has allowed me to design, create and prototype components ever since I put it together. It has been a remarkable tool that these days I am almost unable to do without.

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My first 3D Printed Robot

In just a few short years home 3D printers have gone a long way and are now no longer just hobby kits but real plug and play devices. If you are into home robotics this is definitely a tool you should consider purchasing.

 


Max’s Mask – The Eye

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Robots perceive the world around them using sensors, think and plan their next move based on the information using a brain (micro-controller or computer) then finally react using actuators or another output (such as an LED). This is a basic concept of robotics.

I want Max to understand the way in which a robot sees the world and can respond to it. The mask I am making uses an Infrared (IR) LED to produce IR light like a torch that humans cannot see and a detector IR photo-transistor (which looks like an LED) to sense objects in front of the mask. IR light bounces off an object ahead and returns and activates the IR transistor. This is essentially a robot eye that can see a single spot and determine how far away that spot is.

The sensor works by using the voltage divider rule. As IR light from the LEDs is reflected off a surface back onto the Infrared Photo-transistor the resistance of the circuit changes as the transistor is switched on and current is allowed to flow to ground (GND). The varying changes in resistance cause changes in voltage measured on the signal wire. You can then use a micro-controller to measure the analogue voltage signal. You can then use this to approximate a distance.

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Infrared Eye Circuit

I prototyped the circuit using an Arduino microcontroller to test the Eye. Arduino is a great platform for prototyping electronics with software and is cheap and very easy to learn. There are so many resources on-line which will help you develop electronics using the Arduino.

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Prototype IR Eye using Arduino

Once I was happy with the performance of the eye, I soldered it to a small piece of Vero board and created the circuit for the Eye.

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Final IR Eye

I will provide the full design for the sensor in the final tutorial guide.

Great Expectations

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My nephew Max is 7 and over his very few years he has managed to become intrigued with Robots (go cool uncle Luke). Seeing his great granddad and I fix and make electronics and robots he now wants his own personal robotic armada to play with. So he asks me to make him robots.

He has become very good at drawing and gives me pictures of his robot “orders” so that I may build them for him. His drawings are of robots he invents in his mind and sees on the TV, so his expectations are quite great (one of his requests was an Iron man suit).

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Magnet Man

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Max’s Mask

When I see him at his grandparent’s place he always asks me to build a robot with him. That’s fine for me as we pull out the Lego, however he wants a real one not Lego. Also he does not yet have the patience to understand that it takes weeks and months to build a robot.

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A very impressive robot arm

Although I am older, I still manage to give myself great expectations for what I would like to build. It takes time working on a project to realise that adding wonderful features and big ideas are not always feasible due to time, cost or technical difficulty. Building small and learning as you go is always the best way to learn robotics. Don’t fall into the trap of trying to build a robot that does everything all at once, but start small and add to one or build many in a steady progression.

A while ago Max asked me to build him a mask with robot arms off the side and can help him fight baddies. So instead I have decided to start small and build him a mask that uses some basic principals of robotics. More details to come soon.

Robot Chassis – The Skeleton

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I still remember the first robot I built at home. Although I have no photos of it I still remember the mess I made putting it together. I spent hours cutting and carving Styrofoam to make an oddly bullet shaped pancake that was about the size of an A4 sheet of paper. Tiny foam balls flew everywhere and statically stuck to everything as I tried to insert my Basic stamp education board by squashing it into the square “like” hole I cut into my robot chassis. My 2 modified servomotors (for continuous rotation) were positioned awkwardly at different angles and heights, held in by screws even though sticky tape would probably have sufficed.

Wires hung and dangled on the floor and in the air connecting the micro, sensors, power and actuators with extreme complexity so that no-one (not even I at times) could determine where they were connected to. While putting it on the ground a small and gratefully unused chunk of the robot chassis broke off. My robot maiden run was not going so well. However I had managed to scrape together some decent code off the internet so my PING sensor managed to keep my robot from bumping into obstacles and loosing any more pieces of itself.

The robot had many flaws. It would not drive straight (due to the positions of the servos in the chassis not being aligned), it would break apart and leave foam all over the place (due to the chassis material being too brittle) and wires would come loose shut down the robot and I could not work out quickly where to put them back (due to poor wiring and messy prototyping). All of these issues could have been solved with some forward planning and measurement rather than just trying to cobble some “stuff” together. My first robot was not just a failure in building and construction, it was a failure in planning.

A robot chassis is the skeleton of a robot and good working robot requires that its skeleton be robust and precise to ensure its correct functioning. A robot will never work properly if it is not created with its intent, environment and construction planned out before you design it. Whenever you begin to design mechanical parts I have found it best to ask the following questions:

  1. What do I want this robot to do?
  2. What will be its operating environment/conditions?
  3. What method/process will I use for construction?

The first question will highlight the critical aspects of your chassis design. For my first robot I wanted it to drive around and avoid obstacles therefore it needed to have equal motor drive balance. So making my robot symmetrical with both motors balanced was critical, something I definitely did not do. What your robot is intended to do will form its skeleton.

The second question will help you to determine what your robot chassis and rest of the body should be made from. Is your robot going to be operating outside on the grass, underwater, on tiles or wooden floors or will it be on carpet inside the house.The environment in which your robot operates will give you the requirements of what it must handle in its life, so you should design accordingly. My robot needed to be robust enough to handle just being handled, to that criteria it failed. I cut the foam for its chassis too thinly and it could barely hold the weight of all components when handled without cracking and breaking. Some 10mm perspex sheet would at least provided some rigidity to hold the robot together and not fall apart.

The final question is a must for designing anything. How will this be made? With your materials selected from the last question you can now see how to make parts using that material. All processes have their strengths and weaknesses. You may be limited to what tools you have access to so that may also limit your construction abilities and techniques. You MUST design with the way it will be made in mind, my robot was carved out of foam using a knife and a short battery powered wire cutter. My first intricate and dimensioned drawings of the robot had no chance in reality of being produced by hand with those basic tools. I was not able to make the proper measured and accurate cuts that a machine could do without issue. Rigid materials for robot chassis’ require power tools to cutout with speed and accuracy.

I have completed the build instructions for the Prototype robot chassis/shell. I do not have as many photos as I would have liked, but I did not think of writing this blog until half-way though finishing. The method used for this shell is the same used for fiber-glassing boats and making models. It provides a very strong structure and can be finished with paints. I hope to use this method in the future to complete a robot, but that is for another time.

Building Robots in Apartments

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Living in an apartment in Sydney has its advantages. Rent is cheaper, I can live close to the city, not a big area to clean, etc… There is however one big draw-back  for any Maker, Inventor or Engineer, the lack of working space. I do not have a garage, shed or workshop space. Anything that requires mess (sawdust, plastic or foam) from sanding, cutting or spraying must be done in one of the rooms or on the balcony and will likely go everywhere. Building robots did not seem to be compatible with living in an apartment.

I found this out the hard-way when creating the Prototype chassis. Sanded foam, shards of cut fiberglass cloth, sanded putty and epoxy resin was all over my apartment and in the air which did not impress my wife at all. The whole process made me really think whether or not I could build anymore robot chassis in the future at home and whether I needed to move my work to a better, however less convenient environment.

Using the trusty Google, I looked up as many ideas as I could regarding apartment working or apartment workshops but did not find much. After much searching a chanced upon an Instructable (which is a great place to find ideas and plans for makers) for a DIY Anaerobic Chamber. The concept was great for what I wanted. So I created a version for myself that would allow me to keep contained all the dust and mess that I had been creating in making a chassis.

I have documented my build in the Projects section under Apartment Work Space Box.

Has anyone else had issues making or inventing in apartments? How did you overcome these issues?

Unusual Robots

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I like my robots unusual. The weirder the better. Stargate Replicators (bugs – not the human looking ones) are my favorite. They always gave me the impression of robotics and nature meeting, the robotic ants that take over worlds. In current robotics they would be categorised as Swarm Robots which has always been a particular fascination of mine. Simple robots with simple behaviors and abilities that work together with the results being emergent behavior that gives the impression of a higher intelligence.

I have always wanted to build robots such as these, but this is a very far off goal as anyone who has started a robot project would know very well. So to start I want to build a robot that is simple and work towards my goals into the future.

First things first. Whenever I have built a robot I have started very well, bought all the electronics and mechanical pieces and started to put things together with limited success and finally ending up procrastinating and abandoning the project or starting something new. Also when I show my wife, friends or family what I have built I am usually greeted with funny looks and the usual “what is it?” and “what does it do?” question. I feel that I am missing the WOW factor in my robot building.

I am usually WOWed while watching Sci-fi shows and the robots they create. Another favorite of mine is the Farscape DRD which is a very cute driving robot. I will begin my robot making by building the outside shell first to give the WOW factor that I hope will keep me motivated to continue the project to the end. I want an unusual robot to give me the WOW but I need to learn how to do this. In the next few weeks I will look toward making a great model for my robot to fit in.