Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

Hull Pixel Bot

by RobMiles, published

Hull Pixel Bot by RobMiles May 5, 2016
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Hull Pixel Bot by RobMiles is licensed under the Creative Commons - Attribution license.

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Hull Pixelbot

Welcome to Hull PixelBot. A slow moving, easy to make, Arduino powered, tiny robot

.I'm using very cheap stepper motors which seem to work fine. They are a bit slow, but they provide a precision of movement which you just can't get with standard DC motors. I'm also using catapult ammunition (really) for the caster and four AA batteries provide the power.

There are holes you can use to attach sensors and I'm going to work on remixes that can be used to move pens and, eventually, making a moving pixel display (if I can get enough of them together).

More detailed build instructions along with programs will be going up here.

Construction Details

You can make the Hull Pixelbot in stages. The files have been ordered to make this simpler. There are separate files for left, right, front and back elements. At the moment these are identical, but that may change in future.

You can use M3 bolts to hold the robot together. The holes are the right size for the bolts to engage with the filament and hold the robot together. You'll need 6mm, 10mm and 16mm ones. You can find a list of the other components you'll need here.

Basic Chassis

To make the basic chassis you'll need a base, top, motorTowerLeft, motorTowerRight, skidFront, skidBack, wheelLeft and wheelRight. If you fancy adding style, you can use alloyWheel. It's quicker to print too.

If you want to mount a power switch on the rear you can print out powerSwitchHolder. If you want to add a distance sensor and three light sensors to the front you can print out distanceSensorHolder.


You can add either a single pixel on the top, or a ring of pixels. Either way you'll need to print out ledSupportLeft and ledSupport right. When you mount them, make sure that the square holes in each face inwards.

If you want to add a single neopixel you can print out the ledCrossSuport and shade elements. If you want to add a ring of neopixels (much more impressive) you can print out ringCrossSupport and ringShade. I've been playing with shades that contain light pipes, you can too if you print out ledPipeShade. The shades should be printed out in white or clear filament. All the shades are push fit.

If you want to add a pixel to the back of your robot, print out shadeBase. The shade will fit on this.

Adding a Breadboard

You can add a breadboard, mounted on top of the Arduino Uno. The breadboardShelf is bolted over the Arduino using the same screws.

Carrying Cheese

If you want to carry cheese, or other small comestables, you can print the cheesePlate. That fits around the large pixel and has a brim to stop your camenbert hitting the carpet.

Version 3 Upgrade

We are now up to version 3.0 which has quite a few improvements and extra bits.

  • There is a new wheel type (alloy?) which has a specially designed edge profile to hold an elastic band as a tyre. It also has bolt holes each side so that you can tighten against another bolt if required. The size of the slot has also been tweaked to provide a tighter fit on the stepper motor.

  • We now have fittings for a 12 pixel ring as well as a single led. This looks really good. There are two shades for the large ring. One just covers the entire ring, the other contains 'light pipes' that make it possible to discern individual pixels on the shade surface.

  • The led supports have been increased in length to make it easier to fit higher circuit boards underneath.

  • I've added a tray that you can mount on top of the Arduino. This can take a tiny breadboard to make it easier to add additional components.

  • There's also a cheese tray that fits over the pixel, should you ever want to use your robot to move cheese around.

Thanks for building folks, and keep the comments coming. And pictures. Want pictures.

Update: Made a tiny change to the distance sensor and the rear light supports to stop them from fouling the bolt that holds on the front skid.

Print Settings

Printer Brand:




Doesn't Matter


Doesn't Matter






I used a brim to stop the edges from lifting, apart from that it prints absolutely fine.

I printed the shade for the lights using the "spiralise outline" feature of Cura to make the layer as thin as possible. The neoplixels I'm using are so bright that this actually worked rather well. See the website for details of the pixels I used.

How I Designed This

Designed with Python

The entire robot was built using a Python program running inside the FreeCad design tool.

It turns out that I can't do 3D design, but I can do programming.

Three HullPixelBots on the rampage

Pixelbots being controlled over MQTT using an Azure IOT Hub.

Displaying patterns usign massed Hull Pixelbots

The original platforms, doing the Hull Pixelbot dance.

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There's three shade.stl files. And some other duplicates. Are they all needed, are they different versions ? Can you prune to a minimum set of V3 or explain what to do ?

Sorry about the confusion. I've pruned the files and added a description of each build phase.

Hi Rob
I tried to download the files of which I was mostly successful with .. unfortunately I am unable to open the "files" folder due to a "Certificate Trust List" error ... any ideas?



Ah. I think that is because STL files (the designs for Hull Pixelbot) have the same language extension as certificate files on Windows. If you open the files using your slicing program (for example Cura) then they'll work fine.

Thanks Rob. I worked it out after I sent the email. I downloaded solid works and opened them via eDrawings 2014. Most parts ordered via eBay.. hopefully I will gave them before next meeting