Enhanced Spider Robot

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About: My goal is to captivate, inspire and engage young engineers through intriguing robotics projects. I use Arduino at my robotics workshops since it is the most cost-effective way to build a robot using commod...

I’m always looking for a new project to do at my robotics workshop for kids. While spider robots are intriguing, almost all of them are either too complex involving 10+ servos or way over-budget for my workshop. In search for cheaper alternatives, I found this project: http://letsmakerobots.com/node/38744. Since this project appears to fit my budget range of $40-$60 and not too difficult (I think) for kids to work on, I decided to build a prototype. My version will have two operating modes:

  1. Remote control using bluetooth module (HC-06) and an Android phone app. This is the default start-up mode.
  2. Autonomous line-following. This mode is selected through an Android phone app.

Let’s start building.

Step 1: Parts and Tools

  • 2 x Spider robot kit. (Buy two kits from robotshop.com (http://www.robotshop.com/en/dfrobot-spider-robot-frame-kit.html), Amazon, Ebay, or Aliexpress)
  • 4 x Ni-MH battery/charger combo and AA battery holder
  • On-Off Switch
  • Mini breadboard
  • Arduino Nano (cheaper compatible works fine)
  • Motor driver (Using TB6612FNG breakout but L298x based driver should work just as well)
  • Bluetooth HC-06 module (mine is model fc-114)
  • 2 x IR line tracker sensor module
  • 9v step-up booster (4 x Ni-MH is only 4.8v. While motors will use 4.8v, I need to boost voltage to 9V to power Nano through Vin)
  • Dupont cables (male to male)
  • Approx 4” x 4” cardboard used as a platform. (This is just a prototype. Who cares how it looks.)
  • Wireties

Usual tools such as a wire cutter, soldering iron, and glue gun were used in this project.

Step 2: Chassis

See http://letsmakerobots.com/node/38744 for building the base chassis. While 8 leg linkages are obtained from a single kit, you’ll need to use following parts from another kit to complete the chassis:

  • Motor and body
  • Axle
  • Leg linkage case without gears (This is used for joining two independent leg linkages)
  • Cross beam

Since the built-in battery housing on the body pieces are not needed in my design, cut off about 3mm from the height and glue the platform cardboard on top. Use leftover plastic pieces to build a truss to support the platform above motors and build mounting beams for IR line tracking sensors between two motors.

As for the on-off switch location, I put that on next to the battery pack. This required cutting the plastic underneath the platform. I think the better location would be between the cardboard and the plastic body underneath the cardboard and use a glue gun to secure it.

Step 3: Electronics

Wire all the components according to the diagram. You’ll notice that I use 9v step-up boost converter to power Nano through Vin pin. This eliminates having another 9V battery for the logic. Motors are still powered by 6V or 4.8V if using Ni-MH rechargeable batteries.

Step 4: Android Mobile App

While I could have built my own app using MIT App Inventor, why reinvent the wheel when there are numerous already written apps that fit for this purpose? I downloaded few from Google Play to evaluate them and eventually decided to use Arduino Bluetooth Controller. In Controller Mode, I customized following buttons to send specific characters that are recognized by the code.

  • Left = “l” (turn left)
  • Right = “r” (turn right)
  • Up = “u” (go forward)
  • Down = “d” (go reverse)
  • X = “s” (stop)
  • Select = “t” (toggle between RC and Line Following Mode)

See the video on the Intro page to see how the app works.

Step 5: Code

Download the attached Arduino IDE code. Comments in the code should explain what’s going on in the code. It was written for Nano but it should work on other Arduino boards with no or little mods.

Step 6: ​Future Improvements

The kit comes with a motor that is designed for low voltage/high current environment. When using an H bridge driver such as TB6612FNG, it’s better to use high voltage/low current motors. This may explain why, with heavier alkaline batteries, it couldn’t lift the body up to take a step. If you run into this problem, perhaps get a different set of motors such as this: https://www.pololu.com/product/1117. On my other tank project, I eventually had to switch out the motors that came with Tamiya twin-motor gearbox with this one to increase torque.

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    18 Discussions

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    DanaRKelley

    3 months ago

    I made this robot as well... I found the stock motors to work fine. Also I think lithium batters would be better for this robot. I didn't do bluetooth or the optical sensors. My goal is a bit different.

    I added the MPU6050 Gyroscope to use the Z Axis for directional correction and guidance. It does take a lot more time to do this. Not for anyone with limited time. Not for the novice either. Using Z axis and time it will walk a 3 foot square and return to within 4 inches of the starting point on a smooth floor. A word of warning. The motor noise really messes with the MPU6050. So much so it looses all tracking and will hang up. Toroid per motor leads helped. But when batteries are fully charge it still messes the gyro up. I'll need to wrap the leads a few more times to reduce the electrical noise.

    I tried using the accelerometer on the MPU6050 for displacement calculations. It is way to noisy and not sure it would ever work for slow moving robots. Plus the processing to filter the noise is a fair amount of math and requires a software fifo. That would eat up Arduino resource pretty quick.

    Currently researching other methods to track displacement. The goal is to return to the origin after walking around quite awhile. Currently investigating using an optical mouse internals

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    EnesA18

    Question 6 months ago

    You have given the circuit diagram correctly and the cable will be assembled in the same way. as you have given in the picture
    Screenshot_20181222-233350.jpg
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    wkwongss1

    11 months ago

    Hi sir

    The coming academic year I ask student to try out this project

    May you more me more details about how to modify this spider and how to assembly the uno?

    thanks so much

    wkwongss@gmail.com

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    Iffat Bin Islam

    1 year ago

    Awesome project botdemy..... but is there any alternative of "9v step-up booster"?

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    GumdropGary364

    3 years ago

    Nice project Botdemy! One thing though, what is the torque and rpm of the motors? I'd really like to make this fantastic project so please reply quickly! If possible, could you include some links of where you got those motors.

    Thanks

    GumdropGary

    4 replies
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    botdemyGumdropGary364

    Reply 3 years ago

    Thanks. These motors came with the spider robot kit. See the part list above for the link to the robot kit. The kit is really designed for 1.5V single alkaline battery. Once I joined the two kits together and added extra weight of the breadboard, I couldn't move it with a single 1.5V. I tested with 2 and still no go. Same with 3 x 1.5v. Once I hook up 4 x AA, it started to move but the battery ran out too quickly. That's when I switched to 4 x Mi-NH batteries. I don't think battery is an issue so I ordered 6V 12500rpm motors from Aliexpress. Once I get them, I'll do more testing and post my results.

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    botdemytroylanier

    Reply 1 year ago

    The above video is made with 6V motors.

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    troylanier

    1 year ago

    Did you get a chance to put in the 6v motors? Also, assuming that when you used the NiMH batteries you wired them in parallel to keep the voltage at 1.5v for the motors that shipped originally? Thx!

    2 replies
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    troylaniertroylanier

    Reply 1 year ago

    I re-read your post. You were driving the motors at 4.8v and then stepped up the voltage to power the board. So how did the supplied motors do at 4.8v? Thx!

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    botdemytroylanier

    Reply 1 year ago

    See the video with 4xAA NiMH cells. It is walking. :)

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    blic19933

    3 years ago

    I love it. We did a similar spiderbot last year. You are a west coast version of myself. I have been the volunteer instructor for our club at the local library here in Delaware for about a year. We do arduino, coding, 3D design and printing and other engineering stuff. Check out our Instructables. Keep up the good work.

    sp.jpg
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    botdemyblic19933

    Reply 3 years ago

    Thanks! I've been following you on Facebook as well to see what kinds of cool projects you're doing at the club. Keep up the great work!