EOMA68 Computing Devices

An Earth-friendly way to easily upgrade and fix your own computer

Aug 15, 2017

A20 2.7.5 HDMI Design Review, 3D Printing Underway

by Luke Kenneth Casson Leighton

This update will be short: it’s been heavy going for the past couple of months: a lot of focus on very detailed work, for very long hours. Thank you very much to Richard for the extremely detailed and comprehensive help on the HDMI signal design. Pretty much every single message in the archives this month (about 50 messages so far) is about differential pairs. We’ll go ahead with the 2.7.5 pre-production prototypes when a full review and audit has been carried out… and not before.

The 3D printer design is an ongoing dual approach: sorting out the Taobao clone, and designing a new printer. Both are part of the strategy of targetting "maximisation of millimetres per second per dollar" in order to be ready for the massive batch of 3D printing for the laptop. Both printers will be made available when they’re reasonably ready on a planned crowdfunding campaign, for which there are at least three people committed to buying them in order to help out: one of whom is a friend who is brave enough to trust me to get one already.

And about that: when I ordered the kit on Taobao (the equivalent of eBay) it arrived fine, no styrofoam protection whatsoever, bits clunking around inside the box, no damage done. When my friend ordered the exact same kit a whopping fifteen part types out of the sixty listed on the attached BOM were completely missing. No drive gear, no bearings, no microswitches - nothing. If he had been in Europe that would be a three-week shipping delay and he probably wouldn’t have gotten any response. It just illustrates precisely why it’s necessary to source components yourself from China, and actually have someone that can be trusted to verify them.

Anyway here is the discussion about the Riki200 - the first design concept was a bust. In order to get up and running, I’m trying out the "Etch-a-Sketch" concept, and, once that’s working and I can print out PETG and PolyCarbonate (PC) successfully in order to get reliable parts, I will redesign it to the Ultimaker-2 style belt layout: drive rods and twin belts per axis. Photos, videos and so on are being posted on the reprap forum.


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