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
- 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
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.
