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.

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

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

• 2mm piano wire, length 25mm (e.g.: https://www.hobbydirect.dk/shop/modelskibe-af-trae/tilbehoer/piano-traad-pianotraad.htm).

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

• Savox SA-1230SG https://savox-servo.com/en/product/SA-1230SGplus/savox-servo-sa-1230sg-digital-coreless-motor-steel-gear