As I had said in the first part, this post will be covering the frame of the robotic arm, the power source, the code, and any other miscellaneous items. I have been working with my partner on it, and we almost have a prototype built. We will finish it over winter break. Remember, the best arm in the world is useless if the drivers haven’t practiced using it.
So, the frame. The “backbone” of the arm needs to be very sturdy and stiff. Some people try using PVC piping, the piping used to carry water through a house, however that is a bad idea for several reasons. Number one, is that PVC piping is hard to attach flat things to. Since the servos are flat, attaching them to a rounded object is hard and less secure. Secondly, PVC is relatively heavy, compared to the alternatives. The material that I recommend is aluminium.
Aluminium is lightweight, flat, and best of all, cheap. The amount of aluminium that I need for my arm is about $10 from Home Depot. It is much stronger than PVC, and metals do not bend easily. You may be thinking, “Isn’t aluminium hard to cut and shape?”. The truth is, yes, but you can do it with a simple hacksaw. Cutting it isn’t very difficult, as aluminium is one of the softer metals. All you need are some screws, a drill, and you can mount the servos to it with ease.
Next, we need a power source. As you can imagine, it will be rather beefy and need enough power to run a micro-processor and several servos lifting each other. If you buy a shield, then the shield will tell you how many volts it requires. After you know that, search on a site like HobbyKing for that volt of a battery. Next click on a link that has the most amount of mA, or milliamps. More mA means you can run your arm longer.
One really important thing that you need is the claw. The claw that I am using is from an old toy, and it is shaped like a bowl, but can open and close easily. For anyone else perusing this project, I recommend that you buy something prebuilt from ebay, such as this arm.
Make sure to wrap the arm in some sort of rubbery material so that it has a good grip. I plan on using electrical tape, with the sticky side facing in.
Another thing to consider is the base of the robot. The base will have to have some sort of weight, to stop it from tipping, but it will also need to have the Arduino and the power source housed within. One nifty idea one can use is to simply use the power source as your weight. Most of them should be heavy enough to support the weight of the arm. As for the material, something like a wooden box should be fine, because the weight inside will stop it from tipping over. The wooden box will also be easy to mount things to, such as the power source and the servo to move the entire arm side to side.
In short, building a robotic arm can seem outrageous on paper, but if you spend some time understanding the concepts behind it, you can quickly develop a plan to build one. Part 3 will be coming soon!