Hi guys! Here's a spider robot that we had made for the 2016 science fair which was held at our school. Well, you can't technically call it a "spider robot" as spiders have 8 legs, but we atleast tried to make it look like a spider (or maybe spider like) . Our robot has four legs, so the correct term would be a quadruped. Well guys say hello to "Quattro", a non lethal, arduino quadruped!

Here is an instructable on how we made her, taking you through the building process, getting to the programming and finally admiring the robot come to life once its finally done :) . Watch the video to get an idea of what it will finally look like, the problems we encountered and how we solved it and improved it.

Before going to the next step please note that a laser cutter has been used in the making of this robot. A laser cutter can be avoided if you are very skillful with your hands, as precision is key to completing the project!


thanks for your support.

Step 1: How It Works?

The robot has 4 legs, with 3 servo motors in each leg, which give the legs a freedom of three degrees. We use a simple gait to get the robot to walk which is known as the creep gait .

We used a creep gait as its one of the simplest, slowest and yet smoothest of all gaits. At first we just get the robot to walk forward, back, left, and right and then we add cooler features such as obstacle avoiding and Bluetooth control to take it to the next level.

Step 2: Parts Needed...

The body:

  • 2 mm thick clear acrylic

Bare minimum electronics:

  • 12 servo motors (quite a lot )
  • arduino nano (any other will do as well)
  • a servo shield will surely help (we made one ourselves with some pcb and pin-headers, will explain the process of building the shield in a later step)
  • a power supply (5v at 4a will work great, that's what worked for us) we used a simple wall adapter

Extra electronics:

  • ultrasonic sensor (for obstacle avoiding)
  • hc 05 bluetooth module (for smartphone control)

For the shield:

  • pcb (preferably the ones with common lines for ground and power)
  • female headers
  • male headers
  • wire


  • laser cutter (or skilled hands)
  • super-glue
  • hot glue

Step 3: Laser Cutting the Parts

Using a graphic design software (inkscape, link to this free software below) we designed the parts we would need to make the robot's legs and body.

Then we took the design to a nearby workshop to get the parts laser cut. Attachment below for the designs. After laser cutting be sure to have 30 individual pieces.

Link to download inkscape: link to download inkscape

Step 4: Assembling Quattro

The first thing you need to do after laser cutting is actually the hardest and most time taking thing to do: peeling the paper covering off the acrylic, painfully one by one. At this point I would advise you to catch a friend and ask him/her to help you out. My mom helped me here.

Next assemble the legs. The slots are already made and all you have to do is fit them together. The joints are tight but just for safety you could put a drop of superglue or acrylic glue to really join them together.

To be able to proceed to the next step you need to modify your motors a bit. Glue a bolt symmetrically opposite to the motor's shaft. This gives your motor a dual axis pivot, which helps in making the robot more stable (have a look at the picture above).

Please note you need to do this with just 8 motors, as four will be attached directly to the body.

Next attach the servo motors!Finally attach the legs to the center link joint (the curved piece) and attach the link to the servo on the body (keep referring to the picture on top as the servo orientation will make a difference).

Step 5: Making the Shield

To make the shield for all the servo connections you'll need:

  • some pcb(preferably the ones with common lines for ground and power)
  • female headers (30 no.)
  • male headers (36 no.)
  • some wire

Making the board is quite straightforward follow the picture above to make your shield. Or you could just buy one...

We will be making a separate instructables to show you how its made in detail, please share any doubts or questions in the comments section down below

Step 6: Electronics

Now its time to attach all the servo pins onto the arduino. Connecting them using jumper cables would be really messy and confusing, so use the diy shield, which we made in the previous step . The servo wires need to be connected in the right sequence, this is key to make it work!

Carefully follow the picture.

Step 7: Programming

Now this is the time when your robot comes alive. First upload the legs_init program and make sure the robot is at a position similar to the first picture above. Next upload the quattro_test.ino to check whether your robot is managing to do the basic movements such as walking forward, back, left and right.

IMPORTANT: You need to add an extra library to your arduino IDE now. Link to this library below :


If you don't know how to install libraries to your arduino ide here is a good tutorial on how to do so:

Now she should go forward 5 steps, back 5 steps, turn left 90 degrees then turn right 90 degrees. If she's doing everything right you're on the right track. If not, there might be several reasons it's not working out, explaining all of them here wouldn't make sense, so i'd suggest you drop a comment down below mentioning your problem.

P.S: put a cup as a stand to start with so that Quattro doesn't go all over the place. Once tested and working fine, you could proceed to leave her on the ground.

Step 8: Inverse Kinematics

Inverse kinematics is what's actually driving her. ( if you are not interested in the math behind this project and you are hurrying to finish this project you could actually skip this step, but knowing what's happening "behind the robot" is always helpful.)

In simple words inverse kinematics, for short ik, is a bunch of trigonometric equations that determine the position of the tip of the leg, the angle of each motor, and other values when given a couple of presets that you need to determine. For example, the length of each step that you want your robot to take and the height at which you want your robots body to be at. Using this pre-determined (data) it will derive how much it should move each servo to be able to manage to perform the given task.

The picture above shows the trigonometric equations, developed by a friend of ours in the college, Suman Pal ,who then transferred the mathematics into a program.

The code attached bellow is just the raw formulas that you could fiddle around with to experiment upon, improve and try out better methods.

Step 9: Getting Fancy

Once you see that your robot is managing all the basic movements, you can start to make it fancy. We decided to add an ultrasonic sensor so that it can avoid obstacles on its way. You can also try Bluetooth control or voice control. To do the movements you need to just call a function.

The following list says what function you need to call for what movement :

  • to move forward - step_forward()
  • to move backward - step_back()
  • to turn left - turn_left()
  • to turn right - turn_right()
  • to stand - stand()
  • to sit - sit()

In the brackets you can put an integer value to define the number of steps that you want the robot to move by.

With this added feature Quattro will never touch anything if left in a room. Almost as though she has a mind of her own! Please do share if you add any other interesting features...


And there you have it your very own robot companion! This project gave us a lot of experience and we developed several skills. We would encourage you to make one as its easy to make yet very impressive. The future looks towards robotics and we with quattro have taken our first steps!

We hope you enjoyed this instructables, do leave a comment below!

lastly, we would be grateful if you could vote for quattro in the contest and subscribe to our channel both on instructables and youtube. Thank you for your support!


<p>Hi, how did you connect the sensor to the board?</p>
<p>Hello,</p><p>I am in the processing of this build and trying to look at the code. I have the additional library downloaded and installed but the legs_init file comes up as &quot;sketch can't be created&quot;. Quattro_test opens just fine. Anybody else experience this issue?</p>
<p>having trouble with verifying scetch</p>
<p>Make sure to recheck step 7 and don't forget to install the additional library. </p>
<p>i was wondering if Math.h is something i am missing to get this to work.</p>
It could be, could you tell us whats not working we could try to help you out
Thanks for your enthousiasm
We would be glad to try and help mail us the problem at : technovationrobot@gmail.com
<p>Hello I had a question about the PDF and the laser cut pieces. I had taken the PDF to a local make space and used their cutter to make the parts, however, the scale from the PDF,as is, was too small and could not be harnessed around the servos at all. I like what everything about this for sure, just what scale in inkscape or even Corel Draw does this need to be in?</p>
<p>We don't quite understand the problem as it is supposed to be a 1 : 1 ratio. Any further questions email us at technovationrobot@gmail.com</p>
<p>Hi,great project! very detailed! I am also building a quadruped robot, i 3D printed my parts but i am not good with coding, so i uploaded your test codes and it kinda works. I think i need to change a few parameters. I just want to ask if you set your motors at an initial angle? and where on the robot is length a, b and c and side? And how do you go about calculating z-absolute? </p><p>Thank you</p>
<p>hey, thank you for the support. The motors do need to be set at an initial position, this can be done by uploading the legs_init code in step 7 and making sure the robot looks like the picture in step 7. For the inverse kinematics algorithms the lengths a, b, c are drawn in the little diagram in the 3rd picture in step 8. And for the value of z-absolute, you choose the value depending on how big of steps you want the robot to take. I hope this clears your doubts.</p>
We are very grateful for all the votes we got to put us through to the finalists! A big thanks for your suppoet! Stay tuned for more of our projects...
Go go go !!!
Thank you so much for the support!
<p>Seriously AMAZING work. I've been looking for something like this for my own project, and you've executed it beautifully. Thank you for sharing. :)</p>
Thanks for that wonderful feedback! We would be very happy to help you out :)
<p>Amazing job! Nice work with the inverse kinematics.</p>
<p>Thanks for the positive feedback!</p>
<p>Nice detailed build, with a fantastic outcome. You've got my vote!</p>
<p>Adorable and awesome!</p>
Haha thanks for your support!
<p>Hi,</p><p>I tried to download the pdf file (twice) and nothing came. I tried to download some other pdf file and I had no problem getting them. I am using Macintosh with OS 10.12.2. Any suggestion as to what else I can try?</p><p>BTW, this is a fascinating post for which I thank you!</p><p>Tena Sakai, sakaitena@yahoo.com</p>
<p>Hi tenasakai,</p><p>You could also look at Doug's comment above it might help you.</p>
Hi, I tried just now (which is nothing different from what I had tried before) and I got the initial pdf file (24 pages), as well as ino files that were &quot;imbeded&quot; in the (24-page) pdf files. I am far from having digested material you presented, but at least I am over the first hurdle. I don't understand what I did wrong before, however. In any event, thank you for your posts! tenasakai
Okay! I'm glad it worked...Would be glad to help you with any other problems!
<p>Thank you, Technovation! I appreciate your kindness and enthusiasm, not to mntion being thorough.</p><p>Tena</p>
Always welcomed!
<p>We are not sure of the problem you are facing while downloading the PDF file, will mail them to you right away!</p><p>Thanks for your appreciation.</p>
<p>Hi,</p><p>Thanks for your fast response! The pdf file you mailed me was only one- pager and it is the one called hexy_legs_all.pdf. Would you mind sending me the entire pdf file? Thank you!</p>
<p>Yup sure!</p>
Nice job. Could you post a link to the video mentiones in the article?
<p>thank you. The video is linked right at the beginning after the first 2 pictures, i think you might've missed it by mistake...</p>
<p>Thank you. It appears that for some reason my browser did not render the video. I see it now. Do you know if the motors/legs are strong enough to get the Quadruped to stand up and not drag its 'belly'?</p>
<p>it doesnt depend too much on the motors actually, yes the motors do play a role but what need to be good are the joints from the legs to the motors.</p>
<p>Nice Instructable! Looks like a good future project. Is there a link somewhere to the InkScape file that someone might use to cut the pieces with a CNC router?</p>
Won't it work with the same laser cutting files?
<p>in other words if u wanna use inkscape to upload the file to you laser cutter, import the file as a pdf (the file is in step 3)</p>
<p>Thanks, but no luck so far importing PDF, ungrouping and trying to trace.</p>
<p>If all you want is a different file format (for ex. SVG), use &quot;save as&quot; in Inkscape. If you need a gcode file, use a Inkscape gcode addin. A search of &quot;Inkscape gcode add-ins&quot; will pop up several. </p><p>I also find <a href="http://www.makercam.com/" rel="nofollow">http://www.makercam.com/ </a> to be a very useful tool. It will accept SVG files from Inkscape and outputs gcode.</p><p>If you want to adjust the parts of the robot (for ex. different thickness of plastic, different servos, etc...), the procedure below may help you:</p><p>Select one of the parts do copy/paste to new instance of Inkscape, ungroup and select the two or more parts that make the perimeter. Perform Path-&gt;Combine on the selection. Change the part as you need. Select all the portions of the part and Group.</p><p>Make Clone Array of eight new parts and delete the initial part (there will be the initial part and a clone on top of it). Do it to all the parts of the robot. </p><p>There are only two parts that are not single paths.</p><p>If you want to adjust the single path parts, perform a Path-&gt;Break Apart to access the internal objects. Group the part after you have broken it apart as you desired.</p><p>I usually change the stroke color of the internal geometries of a part while i'm at it.</p><p>Save the new file after you have all the parts.</p><p>Hope this helps</p>
<p>Thanks for your support!</p>
<p>Thanks Doug, very helpful!</p>
Just saw Quattro great work! Thinking this would be a great cross course study project for our Computing and Engineering students to learn together and experiance working with people in other fields from your own. I used to work in the Computing Dept but I still stay in touch; I think the Engineering Dept have a lasercutter. I do know that computing has a 3D Printer. Have you tried making the parts in 3D instead of Laser? Let me know what you think. I am going to pass your project to my colleges at Tresham College here in the UK. Thank you.
<p>We are very pleased that you've found our project interesting and useful for a class study project. We will be glad to share information that you or your colleagues may require.</p><p>Regarding your question on 3d printed parts, it is surely possible, but in our case we chose to laser cut them because it was simpler and cheaper.</p><p>Look forward to hearing from you.</p>
Great built. Nice job. Voted for u :)
<p>Ahh,very well built my friend.A remote one next time??voted as well</p>

About This Instructable




Bio: We are two young inventors, Kousheek Chakraborty and Satya Schiavina, with the dream of becoming the craziest scientists. We like making robots and bringing inanimate ... More »
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