Introduction: BOBBY the Bear - Arduino Halloween Decoration

This project is made with Arduino and it consists of a spooky teddy bear.

This mysterious little bear may seem all nice and cute at first sight, but as soon as you approach it, its head turns around and the side you start seeing shows a tiny bear coming out of its head and it looks eerier and scarier. Also, his eyes light on thanks to a couple of RGB LEDs and a startling sound starts coming out of it. This can be a great decorative item for this Halloween season, as it will definitely creep out all of your guests and you will surprise them with innovation and originality with this unusual decoration.


Electronic supplies needed:

  • Arduino UNO (x1)
  • Protoboard (x1)
  • Jumpers Resistor RGB LED (x2)
  • Servomotor (x1)
  • Ultrasonic sensor (x1)
  • DF player (x1)
  • Speaker (x1)

Supplies and tools needed:

  • Teddy bear (x2)
  • Box (x1)
  • Cuter (x1)
  • Wires
  • Red nail polish (x1)
  • Vegetal paper (x1 DIN A4)
  • Sewing thread (x1)
  • Needle (x1)
  • Soldering iron (x1)
  • Soldering wire pond (1m)
  • Wood (42 x 42 cm surface)
  • Mechanical saw
  • Mechanical drill


Circuit mounted on the software TinkerCad to check beforehand the proper operation of the connected components.


Creating a diagrammatic representation of an algorithm through a flowchart, allows us to make a step-by-step approach to solve the desired task before getting hands-on with the actual code needed for Arduino.


Once we have all the components connected on the protoboard the way it is shown above in the schematic section, we can connect the Arduino UNO to our computer and upload it on a sketch in the Arduino software.

Code needed for this project:


1. Before starting what will be the more artistic part of the project, we recommend handling the electrical part of assembling all the components needed the same way it is shown in the scheme above on the electrical connections section. This way, you can make sure that everything works alright and you will start having an idea of how much available space you are going to need inside the bears to fit everything.

We did not weld all the elements to the typical bakelite plate, as this kind of project did not require it. However, we decided that it would be better if we welded certain elements with its respective jumper, through cables from which we first stripped the ends. This way, we can work with larger distances between all certain components.

2. Once all the electrical elements are set, we can start the exterior part of the project, make what people are going to see.

Here, everyone will have a certain degree of freedom, as each person carrying out this project can prepare their own bear according to their own taste and design its appearance however they like best.

3. First of all, we will be doing everything related to the big and main bear.

First, we need to cut the bigger bear’s neck around and empty out the mid-lower part of its body a little bit so we have it ready for when we have to put all the components later on.

On the other hand, we need to cut a hole on the back of its head, which will be the space from where the smaller bear is going to be coming out, and paint a little bit around that hole with red nail polish, to make it look like it’s bleeding.

Be careful with the size of the hole. Don’t make it too big because then, some empty space will be left and the little bear can fall out. Don’t make it too small because the little bear will not fit in.

4. Then, as we emptied out the bear’s head, we needed to create a simple structure in order to keep it looking straight. We can achieve that by putting together some wires, the way it is shown in the picture, and then putting all the structure inside the head.

Be careful with the wires, do not hurt yourself with the cutted tips.

5. Next, we take care of the little bear that will be coming out of the big bear’s head. First, we need to cut its legs so it can enter easily in the hole made before.

6. Now, let’s take care of his look, let’s make him look scarier.

First, we need to make a couple of diffusers, one for each eye, so they can scatter the light out and create a softer light from the LEDs.

We made a cylinder with film paper and left one side opened so we could insert the LED.

As the bear we got was all tiny, cute and with a big smile, we decided that we also needed to cover that up a little bit. That is why we decided to put a couple of big-white teeth with some more nail polish, so it would look like blood.

We did them using FIMO, some kind of clay, that when you have modeled it, you bake it for half an hour and it gets hard. Then we painted them with white and red paint. We sew them to stick the teeth in the little bear’s smile.

We also sewed a little scar in the little bear’s forehead and we painted it around a little bit.

Once all of that is finished, just add some nail polish to those areas that you think that may need another artistic touch and add the details that you think are necessary to both bears.

7. At this point, we can see that we may have placed too much weight on the upper-side part of the bear, which can be dangerous as it could mean that the heads won’t turn around properly so, before putting the arduino and make it functional, we decided to add a heavy structure to the bottom part.

To get this structure, we cut some thick squares (7 x 7 cm) of wood and piled them together. But, in the last piece, we added a central cut with the shape of the servomotor. This way, we achieve that the motor doesn’t move when it turns around, allowing that only the head turns smoothly.

8. Finally, we just need to put all the Arduino components inside the big bear’s belly and once we have our code uploaded to the Arduino app, everything is ready to run.


Fear is triggered by those things that we do not expect that are about to happen.

This is why this bear is great for this Halloween season, as the only thing that you see at first sight is a small and cute bear and you just do not expect anything to happen and it will for sure be different from what your neighbors set up as their own decoration.

As we have explained, it is not difficult to carry out this project, as the only things that you need are an Arduino kit, all the materials shown above and your willingness to have some fun during this whole process.

On a more personal level, the results obtained are satisfactory, but due to the crazy circumstances that we are living in right now, we have not been able to work in the whole process together and some of the parts have been difficult to carry them out the way we would have liked. Nonetheless, we have had a lot of fun during this whole journey and we have achieved positive and gratifying results.


Project made by: Gemma Carbonell, Judit Gisbert, Yana Gusyeva

Halloween Contest

Participated in the
Halloween Contest