Introduction: Heartcrab: a Lambada-Walking Robot in Your Pocket!

About: I'm Mario Caicedo Langer (M.C. for short), a Colombian STEAM educator living in Azerbaijan, BSc in Naval Sciences and former Navy officer. I am a CAD and 3D Printing enthusiast and an artist specialized in jun…

This is one of these projects with multiple meanings: is this the cheesy relative of the "headcrabs" from the Half-Life video games? Maybe a walking robot in love with a ladybug? Or is the ladybug piloting her own mech?

Whatever the answer, one thing is for sure: this robot is happy with its ladybug and walks in a very curious and rhythmic way. Maybe it looks erratic at the beginning, but if you watch it carefully, you will see this little bot has Sabor Latino. This robot walks almost like dancing... LAMBADA!

I wish I could say this is the result of a strict engineering design process and meticulous calculations. The reality is, this is an unintended consequence from a failed project (I was trying to make a mini-submarine, go figure). But some of the best things of life come by accident. And I'm happy with that! At the end, you can bend the legs of this bug, so you can keep it in your pocket and give it later to your significant one.

OK, let me show you how I built this little guy. I cannot assure you will obtain the same results with your available resources, but I maybe you can make your robot to dance "Despacito."

Step 1: Materials

Like most of my projects, I used recycled materials. If you cannot find the exact ones, try with substitutes:

  • 1 x plastic heart: you can get it from thousands of products, like pencil sharpeners, jewel boxes, toys and so on. Or you can 3D print your own one.
  • 1 x micro motor with gear box: you can find it inside 3D pens, or buy it online.
  • 3 x 3D glasses (you know, like the ones you are not supposed to take out of the cinema...)
  • 1 x 3.7V lithium polymer battery: from a broken 3Doodler 3D pen.
  • 1x 330 ohm resistor (orange/orange/brown/gold)
  • 1 x LED
  • 1 x Switch
  • 1 hard plastic piece (white): for the crank. I got mine from a broken printer.
  • 1 plastic small case (orange): to house the micro motor in the heart. I got mine from a toy.
  • 1 plastic small stick (red).
  • 2 long bolts, with nuts and washers
  • 7 small bolts with nuts: like the ones for small electronic and robotics projects.
  • wires: black and red
  • Soldering tin
  • Superglue

Also, you will require the following tools:

  • Dremel rotary tool
  • Heat gun
  • Soldering iron
  • Hot glue gun
  • Screwdrivers
  • Pliers

Also, probably you will need a charger for your battery. You can find it online, or create your own one.

Step 2: Crank

Using the Dremel, I cut a piece of plastic and adapted it to the gear box. It will work as the crank to move the legs of the robot.

Step 3: The Centre of the Heart

I drilled holes in the center of the small plastic case and the center of the heart.The holes had to be tight enough to keep the motor in place. I added a little of superglue to attach both cases, being careful to avoid contact with the gears. Then I put together the three pieces.

Step 4: Nuts, Bolts and Washers

I drilled two holes in the heart, one in front, one in back. I inserted the long bolts through them, then I fixed them firmly using washers and nuts. These bolts will become the axles for the legs.

After that, I added one more nut on each screw, a little bit under the level of the crank. Those nuts will keep the legs in place. I added a drop of superglue to keep the nuts in position.

Step 5: Electrical Circuit

Here you will find the basic electronic schematics of the robot. Its basically a motor in parallel with a LED, with a 330 ohm resistor to avoid an overcharge,

I must recognize that I use Tinkercad almost every week, but this is the first time I dare to use the circuits designer. It's pretty great! I only needed it to illustrate this simple circuit (I used to paint it by hand or in a PowerPoint slide), but probably in the near future I will start playing more with this tool.

Step 6: Battery

My broken 3D pen came with a double-pack battery. To distribute weight, I placed each pack on each side of the heart, passing they connection cable through the small space between the orange case and the heart.

After I found the best place for each battery, I used hot glue to keep them attached to the heart.

Step 7: Switch

I cut the plug out of the micro motor, so I could have its wires free for the next steps.

Using the Dremel, I drilled a rectangular hole on the heart, where I could attach the switch. I soldered one wire from the motor to one of the pins of the switch. Then I soldered another black wire to the center pin.

I attached the switch to the heart, using two small screws.

Step 8: Sockets

To charge this robot, the battery must be unplugged from the motor and connected to the charger. That means we need a mini socket compatible with the battery plug. Luckily, I could extract one from the board of the broken 3D pen from where I got the batteries. I soldered one pin of the socket to the red wire coming from the motor, and the other pin to the black wire coming from the center pin of the switch. Before soldering, I placed some heat-shrinkable tube on the wires, so later I could cover the soldered points and avoid short circuits.

Step 9: LED

I drilled an extra hole on the heart and soldered a red and a black wire to the motor pins, so I could connect the LED. Then I drilled a new hole, opposite to the switch, where I could insert the LED.

I soldered the resistor to the LED's anode, and then I soldered to it the red wire. I soldered the black wire to the cathode. Then I proceeded to test the circuit: the motor was rotating and the LED was glowing!

Step 10: Hips (part 1)

I removed the temples from a pair of 3D glasses. Using the cutting disk of the Dremel, I transformed them in two flat sticks. Then, I drilled a hole in the middle on each one.

Step 11: Legs

Following a similar process, I took the other two 3D glasses and transformed the temples in 2 pairs of legs. Then I drilled a small hole on top of each one, so I could attach them later to the "hips".

Step 12: Hips (part 2)

Using the hot air gun and a piece of wood, I heated and bent both ends of each hip. Then I drilled a hole on each end, to attach the legs.

Step 13: Integrating Hips and Legs

I used the small nuts and bolts to attach each leg to the angles of the hips. I checked they were tight enough to keep the legs immobile during walking, but at the same time, the joints were tested to check the legs were foldable.

Step 14: Integrating Legs Set With the Crank

I took the little red flat stick, cut it in half and drilled a hole on each end. Then I drilled a small hole on one side of each hip. I attached the flat sticks to each hip, a little bit loose to allow articulation. I drilled a hole in the crank, then I inserted the hips through the long bolts. To keep the hips in position, I added a washer and a nut on each bolt, and attached the available end of each flat stick to the hole in the crank, using another small bolt.

The nuts and bolts in this step must allow the free articulation of the mechanism, without being too loose. I added a little drop of glue in the union between nuts and bolts, to avoid disassembly caused by the movement.

Step 15: Last Details

I cut the remaining segments of the long screws and put some shrinkable tube on each feet to improve traction. I placed a little crafting ladybug on top of the motor.

And now... my Heart will go on!

I wish happy life and happy making for everybody! :-)

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