Let's Make Robots!

Yellow Drum Machine

Drives around and finds stuff to play drums on. Samples what it plays, and play to the samples.

How to make a Yellow Drum Machine



Audiofile Engineering asked me to make a robot like this for them, to be won in a promotional contest. Yellow Drum Machine II is done now, and it can be found here.

.. There is always more fun to do with this robot, but for now I will just mark it "complete" in the current version, hope you enjoy it.

Notice how the robot first plays on the object it finds (or is forced to find by the angry cameraman), plays a small beat, and records the beat it plays on it. Then this recorded beat is played again, and it starts to play on the object (an belt tracks and everything else it has),and also playing this sampled beat :)

Also some videos from construction and tuning-time..

What it does? Basically:

  • Navigate around, collect some data, avoid obstacles, until it
  • Finds something "worth playing on" (a single isolated object or a wide flat surface that it can find an angle onto)
  • Snakes into place
  • Plays some beats on what it have found, and samples this, checking it has a "good sound"
  • Based on data collected in the area, and sample just made, then compose a little rhythm, and plays this along with the sample

Why? Well.. I was sitting thinking what I should do for my next robot, what it should do.. Listening to music.. making a rythm with some robot-parts.. Thought; "Hey, I will make a robot that drives around and plays on stuff"

It is just made with sticks mounted very fast with a melt glue gun. But it is really solid still.


Under neath is speaker and a microphone.

The speaker is used for beeps from the microcontroller, and to make click-sounds to the beat. The click-sounds are simply made by setting a pin high and then low straight after each oter. This way I can have the Microcontroller make sound to the music it is also playing, without using any time / causing delay.


The microphone (located on the stick between the two motors) is used to sample sounds and take input, measuring if the sticks are hitting anything or not.

Also it can be used to detect a foot stumping on the floor or someone clapping, and so the robot can find the speed of this after four beats, and play along / fall in to your clapping or stumping.

And.. It can be used when there are kids playing with the robot; Signals "Record", the kids shout, and the robot then plays music / a beat with their shouting as a part of "the music" :)


This robot is made interely without servos. The drumsticks (The "Bass Drum" on the picture) are just these litle geared motors that I am quite fond of.


At the top there is another speaker. It is quite too large, I know, but I thought it looked cool :D Also because it is so torn and twisted, as I could not get it out of it´s old cabinet. On the top-speaker there is a red LED. It lights when the robot is recording, and gives a small blink when it is playing back a sample.


As said above, there is no servo on this robot. The head is also using the little motors from solarbotics. It was, however necessary to use some very thin wire to connect the SRF05, as it otherwise would sort of jam the head now and then if I was using my standard blue wire.

It was quite a fun challenge to make the rather complicated navigation and not having a servo, but only left /right/front to place the head, and then do the rest with the body.

The navigation is complicated because it is not just a matter of navigating around obstacles - that was the easy part. Second the robot has to find good places to drum; A single, isolated object, or a flat wall. Then the robot has to place itself on a good angle to the wall, or straight infront of the object.. All with only L/R/F with the head ;) But it does it quite well now! I am usually amazed of what it finds to play on, when I just let it drive around.


The robot runs for ever on just 4 cells. It must be because the belt-tracks are so geared that there is no strain on the motors.. And no servos, and the sampler takes nothing either.. I dont know, I just know that it runs for hours, more than my wife can stand to listen to - on one charge :D


In the center of this image is a L293D Motor driver. It is just used to enable the head to turn both ways.

Notice how easy it is to mount stuff with this glue; I just thought it would look good there on the side. Put some glue on, and stick it there. Hey, the cables are dangling.. Well.. press then onto the wood, and add a line of glue, bingo!

There is a blue print sticking out behind the wood from a cheese-container ;) That is "the sampler". It is actually this


- And it is just hacked; I took off the switches, and now the microcontroller can record and playback sounds.


- As almost always; Picaxe 28X1 mounted on a standard board. So fast, so effective!!


I think the biggest advantege with building fast as I do (instead of measuring and drawing) - is that you get cooler designs! Lot more soul in this one, than a robot I would make if I was to draw it first..


I know nothing is straight or even or level etc.. But who gives? It is made to play the drums, not to have straight lines :) And trust me; it IS actually quite solid. I will not try, but I am sure it could withstand to be dropped from a table without any harm done.. And if not, it is REALLY fast to fix it again!


Basic construction-materials..


Thanks for listening!

Any questions? If not, then let´s get funky :D





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Hey, Frits. I was looking through my robots parts bin, and I realized that I've actually got almost all of the same parts as you used to build YDM -- I've got some Solarbotics GM3 and GM10 motors, and the Solarbotics tank treads, and even one of those little sampling devices with the microphone and speaker that I bought a while back and never did anything with. So I decided that I really want to build a YDM of my own :) I was just curious if you have any problem with that. Also, if you're fine with it, would you mind sharing your YDM code with me? I think I can handle building the hardware to work similar to yours (thanks to your very clear pictures) but it would take me forever to replicate the behavior from scratch. What do you think? I'd love to have a little YDM of my own running around and bashing on stuff :)


That is really much! I am feeling sorry for you. I can help you make one?

/ Frits


... I'm crying because I don't have a little drumming robot of my own :( 

Hi and welcome :)

I am sure we manage the coding!

It is absolutely possible to make a "homing robot" that finds it way back to the base and re-charges. I know so because they are out there. Though I have no clue how to make such a thing I am sure there are others who can help us :)

/ Frits


its my first time on the site, read every part of it!.. i have never built a robot, but after watching this thing, im giving a try.. i am sure i can get ur help when it come to coding since i havent even done it..

im also into rc racing, so parts and stuff shouldn t be a problem..

i was wondering if anyone has done a robot that knows when it needs power and goes to get power from a specified source? i mean it has a fixed point where is gets energy and when it needs it finds it by is own.. i hope im not being unrealistic..

see you guys,, and keep up the god robots!



This is absolutely fantastic, I love it! I think it's the first time I've ever seen a truly 'fun' robot, and you have inspired me to try to make my own.

Having never made a robot though, nor knowing anything regarding coding, it may be a bit of an uphill struggle, but I'm sure your fantastic blog will help me get there.

Otherwise, where can I buy one of these little fella's? jk, but you should seriously consider approaching a toy manufacturer with your design, I think these would be incredibly popular. Also, if no-one has made anything similar before the Yellow Drum Machine, I think you should definitely patent it. I wouldn't be surprised if one of the big toy manufacturers is stealing your idea as I type!

Keep up the good work, and if I do ever get around to making one, I'll e-mail you the results.

Oh, and also, I love the silhouette photo's, they make me think of Johnny 5.

Thank you so very much for all the "support" and very kind words :)

I really do hope that you try to build your own; It is fun and easy! - And yes, make sure to share your progress and problems with the rest of us!

You are one of a million that tells me to go to toy-manufacturers etc with the robots (specially YDM). But as allways I must say that I have spend much time in my life trying to sell "my great ideas" to such companies, and they just have a wall of defence. Every day they get calls from people who think they have made the next wonder..

Patent - well, been there, done that. I have a patent in China and the US - on some software - but I have found out that apart from being really expansive and time-consuming to get, it does not sell your product any more, so you are back to square one, now you just paid for it ;)

So I am just a happy inventor in general. Robots are just one of _many_ hobbies. Happy because I know that I can just go on and invent, it does not have to be a complicated problem, even if I make some great stuff.. I just throw it up on a web-page or something, give it to somebody, and it makes people happy, and that is fine by me. I just love inventing stuff, and if I can even make someone happy then.. :)

Of course - as allways; Should there be anyone with a rich uncle, or someone in the toy-industry or anybody else with a bag of money who likes what I do, well.. Let's talk :)

Till that happens; Let's have fun, Let's just make robots, I think it is much more fun that way, and we only live once, so let's do it :)

Thanks again. 

/ Frits

You should team up with evilmadscientist and release a kit.
Your playful, positive attitude toward your robot obviously rubbed off into it. It has more spunk and spirit than any of the more technically-able robots I've seen (sure there are ones that can play the trumpet, but can they do it creatively?). It's robots like yours, the various sumo bipedal robot kits and such that give me hope for robotics as something fun :-)

Are you building something?

/ Frits