Step 5: P.1, Plan: Frame and Mechanics

If you're more electrically than mechanically-inclined like me, then assembling a frame for your robot will probably be the most daunting part of this project. Even though I do have some machine shop skills and access, with the competition's time constraint, I decided it would be best to focus on what I'm best at, electronics and code, and find an easy way to get the actual arm together.

Luckily for us, lynxmotion exists!

Their servo erector set parts include everything we need to put together a simple, straightforward mechanical backbone to out arm. Note that the servo brackets and metal horns will only fit Hitec servos, but this can be changed with a little bit of machining to suit almost anything you find on Hobbyking.

Take a look at the bill of materials I've included in the last step to see which parts we bought, and adjust according to your needs. The main types of parts you'll be buying are servo brackets, C brackets, aluminum tubes, tube end connectors, and metal servo horns.

The result looks something like (Picture 1).

As for the gripper, two options exist - I say got for both!

i. Electromagnet

An electromagnet uses an electric current (see: Biot-Savart Law) to induce a megnetic field that can then be used to pick up metal objects, such as the nails and batteries in the competition area. It is generally easier to get working than the mechanical gripper, but needs to be wound by hand on a laminated core from something like an AC induction motor from a microwave fan in order to work effectively. Sloppily winding an electromagnet on an iron nail might work for picking up the nails, but won't do for something as heavy as the batteries.

ii. Mechanical Gripper

A mechanical gripper usually uses another servo motor to open and close a set of jaws that pick up an object. The lynxmotion little gripper is good for our arm, and is compatible with the rest of the lynxmotion erector set.

Where to buy: Lynxmotion Robotics (http://www.lynxmotion.com/)
Servo Erector Set Parts (See BOM)
Little Grip Set

Also get (for the electromagnet):
AC Induction Motor from Microwave Oven
28 Gauge Enameled Wire

<p>For the current science olympiad competition I have constructed a robot arm by modifying the lynxmotion al5d. I am currently utilizing the master-slave system with an arduino uno as the microprocessor. However, I have been stumped on how to power the robot arm. I have been using 2 energizer brand alkaline lantern batteries (6v) in parallel for all of my servos and 1 9v alkaline energizer battery for the arduino. I was wondering how exactly you powered your arm (using what battery) and if you powered it all off the arduino or not. Should I individually power each servo or just collectively and should the servos be wired in parallel or series? Also for some reason, my arm often shakes, twitches, becomes out of control, or simply just shuts off and on repeatedly. </p>
<p>Here is my code for the master slave. There are 2 bases (2 base servos) because each servo only rotates 180 degrees and some of the objects need a larger range of motion to be picked up during the competition. </p>
<p>For the lynxmotion parts, this looks like the cheapest option (incl. servos) :</p><p><a href="http://www.lynxmotion.com/p-1035-lynxmotion-al5d-4-degrees-of-freedom-robotic-arm-combo-kit-no-software-w-ssc-32u.aspx" rel="nofollow">http://www.lynxmotion.com/p-1035-lynxmotion-al5d-4...</a></p>
<p>how well does this unit work for the compatition?</p>
<p>I CANNOT access the BOM, can you help out pls</p>
<p>can you do it with 2 servos and a motor shield?</p><p>if you can that would be great! just leave a link under this?</p>
Hey! Thank you so much for telling us this information. I was wondring why i wasn't able to poen the robotic arm compponents.docx? It says i have to have certain administrative privilges? What does that mean and how do i open it?
hey, my friend and i just joined science olympiad and we're in robot arm... we have no clue what we're doing. <br>where do we even start ? <br>
Read the instructable, then come back with more specific questions :P<br><br>I'd suggest picking a control scheme, figuring out what tools you have access to (can you get power tools, machine tools, CNC machine tools? - your school's shop is often a good place to start), and then putting in a Hobbyking/McMaster order for parts (get a microcontroller, some servos, metal servo horns, and some batteries/chargers at least). My biggest suggestion is to get started asap, as learning to work with the electronics can take quite a while!
yeah our school is willing to buy whatever, we just need to know where to even start when it comes to buying and what we even need. :)
Hi brian
Who is brian?
Well, done, well done indeed! I too am very impressed. Would it be possible for you to post more pictures of the arm itself? I would be very interested to see side, worm's-eye, and bird's eye views. Also, did you cut the aluminum tubing, and if so, to what lengths? Great job again!
As a NSHS alumnus, I have to say I'm very proud and impressed. You've done a great job not only on the project, but on the Instructable. It's amazing what some high school students are accomplishing these days. <br> <br>Back when I was at NSHS, we only had three computer terminals (two ASR-33s and one DECwriter II) hooked up to a PDP-11 minicomputer housed at NNHS (boo, hiss) and we learned to program it in BASIC Plus. In the snow. Uphill both ways. :-) <br> <br>Congratulations! <br> <br>

About This Instructable




Bio: My name is Daniel Kramnik - I like building Tesla coils, quadrotors, and robots!
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