Robobot hardware

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Hardware

All 3D-printed parts are designed in Onshape and are public. They can be accessed at https://cad.onshape.com/documents/fef8699fcafb8aea780c8981/w/ce38e7fdd6cf8533b65e2c3c/e/eefdcf481faf2a4b03f5058c A browser-only CAD tool.

For students, a free account can be created at https://www.onshape.com/en/education/

All items can be exported (in e.g. step format) for import in other CAD tools.

Screws

Mounting holes

The hardware is 3D-printed plastic (except for the electronics and screws)

All 3D printed parts have holes for mounting additional parts. These holes have:

  • Individual hole distance of 1cm.
  • Hole diameter of 2.5mm, intended for 3mm plastic screws.
  • Plastic thickness is 6mm in most cases.

Screws for plastic (PT screws)

Mounting items on the 3D-printed thermoplastic should use plastic (PT) screws.

Plastic (PT) screws:

  • Cut into the plastic with a sharp thread.
  • Gets locked into the plastic.

Plastic (PT) screw selection:

  • Pan-head 2.5mm for PCB mounting, length 8mm, Torx 8IP/TX8.
  • Countersunk 3mm length 10mm, TX8, for the most plastic-plastic mount, where head height is important.
  • Pan head 3mm, length 10mm, TX10, for the most plastic-plastic mount, with space for the head.
  • Pan head 3mm, length 16mm, TX10, for servo arm 'axle'.
  • Countersunk 3mm, length 25mm, TX8, box lit 'bearing' and camera mount.

A typical pan head screw for thermoplastic.

Screws for metal

Mounting of motors and other metal parts should use screws for metal.

Metal screw selection:

  • M3 pan head (For servo horn, 16mm, Torx TX10)
  • M3 countersunk (For motor mount, 12mm, Torx TX10)
  • M5 bolt (For the main wheel fastener, 16mm, Hex/Umbraco 4mm)
  • M5 nut (For the main wheel fastener).
  • M6 bolt (Castor axles, length 50mm, Hex/Umbraco 5mm)

Axles

Castor wheel axles are made from

NB! This is hardened steel and can not be cut by normal cutting tools, use e.g. a Dremel cutting disk.

  • 6mm bearing flange for castor, IGUS iglidur M250 flange bearing MFM­0610­10

Camera

The used camera is a 'Jieli Technology' camera of type 'USB PHY 2.0' (packed by Sandberg as 'USB Webcam 1080P').

The camera has limited control capabilities but supports the following data formats.

  • MJPG coded 640 x 320 pixels at 25 or 30 FPS
  • MJPG coded 1280 x 720 pixels at 25 or 30 FPS
  • MJPG coded 1920 x 1080 pixels at 25 or 30 FPS
  • MJPG coded 640 x 480 pixels at 25 or 30 FPS; this mode cuts parts of the image width to fit the format

It also supports "raw" format as YUYV 4:2:2, but it seems like data loss occurs (fragmented images), so do not use this format.

Servo

The used servo is

Distance sensor

For distance measurement is used

Motor

The motor is CHP-36GP-555 from https://www.airsoftmotor.com/encoder-motor/planetary-reducer-with-encoder/micro-dc-planetary-gear-motor-with-encoder.html

12V with gearing 19:1

Encoder with 17 magnets, i.e. 68 pulses per revolution.

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