Parts specifications


This thread will be used to present the drawings (both fusion and laser-ready DXF files) for the five parts of the chassis.

As the choice and location of the sensors you choose is one of the “free variables” the drawings will not include any openings for sensors etc. Be reminded that everything you use/attach must be within the footprint of the bot itself, with the exception that you can place something on top - as long as it does not fundamentally alter the design. ( e.g. a rotating scanner of some kind mounted on a micro servo would be OK to fit on top).

Updates :

  1. Spec and order link provided for wheels
  2. Spec and order link provided for Servos and trimpots

Notes :

While links may be provided, feel free to buy your parts anywhere (noting that common, low cost hardware is part of the competition spec). Provision of a link does not infer any endorsement of that supplier, it just means that I got it from there.

There might be an update to the drawings for the chassis to accommodate the revised wheels - I’ll make any necessary changes and post the drawings once final (also DXF files that are Sophia-ready )

The price list (assuming you use the same suppliers as I did)

Wheels : £2.90

Servos : £7.40

Controller - £ down to you but keep it simple !

Sensors : £ - down to you ! (see below for line some line follow sensors as examples)

Battery box : 50p

Switch : 50p

Chassis : £4 (two of the 3mm ply sheets under Sophia are required )

Line follow and edge-detect sensors : 70p each (min 3 required)

Running total : £34.79


Wheels !

Well, it turns out that the 60mm wheels were only good for the smaller spline found on 9g servos, and the 9g servos were unlikely to be up to the job.

Specification change is therefore in order, 70mm wheels to be used.

I have just ordered these for the prototype :slight_smile:



Servos !

As stated above, the micro servos felt too flimsy so I have moved to the full-sized item. The servos below are fast and metal-geared so should be fully up to the job. They are not available modified but to rig a pair of these for continuous rotation should only take about 20 minutes - additional parts are required however !

The servos :

Two 5k trimpots required for the CR modification :

I’ll provide advice on how to do the mod on maker nights (or any other time I’m about) .

** * STOP PRESS * ** I just got a job lot of these on ebay - £2.95 each, should arrive in 2 weeks



Sensors :

I got 20 of these (only 19 arrived :frowning: ) from Banggood, they seem perfect.

I’ll not need them all so if you want some, 70p each first-come.

You could also consider using an array ?



The microbit uses 3.3V (max) for power and logic levels - but the servos will require 6V for full performance and that is what 4xAA batteries will provide.

The easiest way to power the bit is to use either a voltage regulator or buck-converter - both options are cheap and simple as very little power is required.

For logic level conversion a resistor divider is the simplest - connect your 5V logic level output from a sensor as below :

<5V output>—33k----66k----Gnd

connect the microbit between the two resistors to get 2/3 of 5V when “high” = 3.3V


Having now assembled the pieces I cut on 18th Jan, I can confirm that this is the final set of drawings.

Assumptions :

  1. You use the same servos and wheels as in the specification
  2. The servos are fixed using screws only, directly into the openings (none of the regular shock mounting hardware used)
  3. You will need to add some openings for sensors / arrays before cutting.

The archive contains both f3d files that can be edited in fusion and “corrected” DXF files that can be imported on Sophia and cut from birch plywood.

Please note that if you edit the drawings in Fusion, you will need to export the final sketch as a DXF, then open that DXF in Inkscape and save it as a DXF (you can overwrite the original) again in order for it to open properly in the laser software.


And here they are:

brace.dxf (12.1 KB)
Disc.dxf (37.4 KB)
upright.dxf (49.2 KB)
DoESbot brace piece.f3d (39.2 KB)
DoESbot disc with no sensors.f3d (58.9 KB)
DoESbot upright piece .f3d (77.2 KB)

OrDoESbot final.rar (179.8 KB)
an Archive with them all:

The bot requires two discs, two uprights and one brace. Plus, four 3mm screws with nuts


This looks fun too


By popular demand, these are the cheapest ADJUSTABLE SENSITIVITY IR retroreflectors I could find.