Let's Make Robots!

Yogy the Yoghurt Tub Robot

Roam around, play sounds, make noises, be controlled with a SNES controller

Again I give you a robot whose pre-existence was that of trash.

A yoghurt tub, given a second chance, salvaged from the recycling bin, I took him in, gave him a new purpose, a better life. This yoghurt tub was destined to be something far greater than a container to house food, he was to be a robot! A robot so cool kids would love him. A robot so cute the parents would watch in awe as he moved around the table. A robot so small, the space left inside of him is limited.

I present to you Yogy, a robot that is kid friendly and parent dazing.

As many of you have come to know me, you know that I love making robots out of trash and this is no exception. I saw this yoghurt tub and couldn’t help but see what it was capable of. The yoghurt tub was the perfect width to house two continuous rotation servos and the perfect height to fit an Arduino and Ultrasonic sensor. So as with everything else I do these days, I set off to work and turned on the web camera, capturing and documenting the whole process.

The parts I used to make him include:

Electrical Parts:

  • Arduino Uno
  • Prototyping Shield + Mini Breadboard
  • 2 * Continous Rotation Servos + 2 * Wheel Servo Horns
  • HC-SR04
  • 8 Ohm Speaker
  • Male and Female Breadboarding Jumper Cables
  • 4 * AA Batteries + Pack
  • 9V Battery
  • LED
  • Power Switch
  • 2 * APC220 RF modules

Construction Parts:

  • Yoghurt Tub
  • Acrylic or a CD (or any other material you can make a base from)
  • Small Square Bracket
  • Small Screws
  • Coke Bottle Lids

And the tools I used:

  • Coping Saw
  • Screwdriver
  • Stanley Knife
  • Hot Glue Gun + Glue Sticks
  • Wire Cutters
  • Wire Strippers
  • Double Sided Foam Tape

 

Now the first thing I needed to do was to make a base to put all the bits and bobs onto, the yoghurt tub would then need to be attached to this base with some screws.

I took a piece of acrylic out of my resource drawers and began to trace the outline of the yoghurt tub onto it. The yoghurt tub itself measures 12cm wide and 10cm high.

Next I had to work out where I was going to place the servos. It was important for this bot that it could turn around nearly on the spot, so its centre of rotation needed to be that of the bot. To accomplish this I aligned the servo shafts at the centreline of the circle and traced around them, this meant of course that there was going to be more room at the front of the robot than at the back, this will come in handy later. I marked where I wanted the servos to go because I needed to work out how big the wheel arches where going to have to be. I am only using the circular servo horns as wheels so the space they need is quite minimal.

Now to cut out the sections for the wheels to poke through I drilled two holes at either end of the arch with a drill bit the same diameter as that of the arch. I then connected these two holes together will a scroll saw, this gives the result below.

After checking that the servos and wheels fit nicely together into their spaces I noticed that it was a little tight, I disregarded it for the moment but later on I did make the arches bigger.

Once I was happy that the servos were definitely going to fit I removed the protective sheet of the acrylic and began the sticking process of the servos to the base. The idea was that I first join to the two servos together at their ‘bottoms’ (please don’t make a joke about that J ) and then connected them together as a singular object to the base, to help improve the bond.

Now I will be powering the servos off a 4.8V rechargeable battery pack, so after I made sure that was going to fit also, I attached that behind the servos, again using double sided foam tape.

I then attached the Arduino Uno on top of the servos again using some double sided foam tape. Because I know the tape can leave a nasty stick residue I made sure to stick it to the clear underside of the Arduino (right underneath the digital pins).

And then I was left with this, looking pretty cool, but still needs a little more work.

 

 

 

 

Now because I wanted to mount the ultrasonic sensor on the yoghurt tub I first needed to mark where it needed to go. Because the yoghurt tub is rounded it made it difficult to mark where the holes needed to go. To combat this problem I made a cardboard template of the sensor so I could stick this onto the tub and mark the holes from there. I did this by tracing the ‘eyes’ of the ultrasonic sensor onto a piece of cardboard.

Cutting that template out.

And tracing the holes onto the tub. I then cut them out with a drill on high speed.

The good thing about the holes was that they were very snug meaning I didn’t need to screw it into position, the plastic held it in place.

Now was the wiring process of the servos. The sad thing I see with a lot of Arduino tutorials is that they power the servos directly off the 5V rail. This is a big no no for me. Power your servos from anything but the 5V rail and just connect the ground of everything up together, like so.

Now Yogy was really starting to look like a robot.

 

Now you’ll remember when I was placing the servos I mentioned the extra free space at the front of the robot, this will be where the 9V will go. I measured up the space that was there and cut a 90 degree bracket of aluminium to shape to act as a guide rail, to allow easy battery change. I hot glued the bracket to the acrylic on a slight angle so that the attachment bracket of the servo behind it would act as an end stop to keep the 9V battery from sliding out.

I made a hole in the yoghurt tub to place a power switch and simply screwed it into place. Connecting the 9V battery up to this switch, with the leads going to the Vin and GND pins of the Arduino.

 

Next I attached the circular servo horns as wheels. Now of course because it was a 2WD bot it was going to need castors. I always have the problem of not knowing what to use as castors, so I spent some time thinking about it. I came to the conclusion that coke bottle lids would be perfect! After holding them up alongside the robot though I realised they were much too big, so I marked and cut them to size using wire cutters.

 

Then after they were cut to size I attached them to the underside of Yogy using some more hot glue, sorry Markus J.

Now I just drilled three small holes around the perimeter of the tub and screwed in some small screws to hold the yoghurt tub into place.

And that’s it! He was finished!

As with most of my other robots however I had to make him better. You can see in the provided videos the extra little features I added.

My 3yo sister absolutely loves him, and my parents think I am onto a real winner. He will be taken to the robotics class on Friday to show the kids and play with.

Once I get a 3D printer I would like to design something similar so that others can make him.

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This robot is adorable! A real Droid! Nicely done, I'm sure the kids will love to build one in your class!

Thank you! :) Well my sister absolutely loves it, so heres hoping the kids at school do too!

You just gave me an idea. Maybe I'll get another yoghurt tub and give it a real droid like paint job, then I can change the bodies around if need be!

Looks like a great first bot project for my 9-year-old and me to tackle with our Arduino. Do you remember which servos you picked, and why?

I'm sure your 9yo will love making a robot with you!

If you would like to make this little robot in particular you can find an instructable for him here.

The servos I used are model sm-s4306r. I choose these because they are high quality factory made continous rotation servos. They are a little expensive however, another option is you can modify normal hobby servos into continous rotation ones. A nice guide for which is here.

Those servos do look expensive, but I'll keep my eyes open for something similar. After watching your video last night, I dug out a 2Cup/473ML plastic container that looks well-suited to the job. The lid seems rigid enough to use as a base, and I might even be able to mount the servos on the underside (the top of the lid), to free up more room inside.

Make sure you post it up here or even make a video response to him atleast so I can check it out when you are done!

Have fun! :D

Hey CP, good project and write up there.

Looks like a nice platform for anyone who wants to jump into DIY robotics quickly, but still build a bot that can be customised and expanded easily.

Thanks TeleFox.

That was exactly what I was hoping for. I would like to take some measurements and try to come up with something similar that can be 3D printed. I like covering my robots with something and I'm not sure how 3D printing something like that would go.

From my experiences at 3D printing on a small printer I can say one thing: printing large parts is hard!

Don't be tempted to attempt printing the largest parts your printer can handle, instead try to think of good ways to break the design down into modular parts. Things will go especially smoothly if you can make several of the parts as identical repeated units.

On that note, I'd consider making a skeleton frame that would both support the internal hardware and also provide mounting points for some external panels... the good thing about using a 3D printer is that you can design the parts so that they snap or slot together without the need for many bolts/screw/hot glue blobs =D

Thanks for that info!

I'm in the process of saving up for a 3D printer now so I am trying to learn as much as possible!

Maybe I'll think of a way for the body section to be printed in pieces that can snap together. If I get something happening I'll post it up here so the feasibility of the design can be scrutinised :).