Printing a handheld PC

robertojones - 2019-01-04 12:42 AM

Quick update on my 3D printed 'HPC'

I've started printing the parts. The CAD design is essentially complete, barring any minor changes I make during the printing / assembly process. Internal components are ready, as are all cables and fasteners and I've reduced the amount of soldering and modification of parts to the minimum possible (I think). I expect to have it built and working within the next few weeks, certainly within a month.

Basic Specs:
- Raspberry Pi 3 B+ 'brain'
- Waveshare 7 inch capacitative touchscreen (1024 x 600 resolution)
- Stereo speakers
- 4 x 18650 batteries (3000mAh, 44Wh total capacity) and off-the-shelf battery management board
- External connections - Micro USB (for charging), 1 x USB2 Host, 1 x 3.5mm audio
- Dimensions - 230 x 130 x 40mm (approx 9.05 x 5.1 x 1.6 in.)

I'm aware that at 40mm thick it's firmly on the 'chunky' side but I'm treating this one as a prototype. I'm keen to get something in my hands (and hopefully a few other peoples' hands) so I can sort out any ergonomic issues for the next version.

The idea I already have in the works is to use a Raspberry Pi 3 Model A (which is a lot less 'tall' than the 'B' and a relatively thin LiPo battery in place of my 18650s. This would allow me to reduce the thickness by around 10mm. Only problem with this is the reduced RAM (512MB vs. 1GB for the 'B' and I would have to do some tests to see what the real-world effect of this and how much it can be mitigated. I expect this to depend heavily on what the machine is used for.

See below for a crude render, apologies for my laziness in modelling the keyboard as a flat 'block', my emphasis has been on ensuring the internals fit and my parts are printable. This is also slightly out of date as it doesn't contain the apertures for the ports or the speaker grilles. I'll try and upload an updated version this evening.

smb_gaiden - 2019-01-04 4:01 PM

Very cool!

Some ideas and questions.

robertojones - 2019-01-05 5:28 PM

Wow, those are seriously small! I particularly like the 'fixed' one with the screen and keyboard parallel, looks like it would be really handy to just pick up for some quick command-line work (as is mentioned on the page you linked).

robertojones - 2019-01-11 7:28 AM

At risk of spamming this thread (please let me know if this is getting too much) I have another brief update, with photos:

robertojones - 2019-01-14 4:06 PM

Thanks Jake!

Dimensions are as follows:

Length (front to back) - 130mm (5.2 in.)
Width - 230mm (9.05 in.)
Height /Thickness (excluding 'hump' for ports on back of screen) - 40mm (1.6 in.)

Weight 970g (2.14lb)

Screen 7 in. diagonal

So probably closest to a Mobilepro 900 in size. I've worked out I can take 10mm (0.4 in.) off the thickness and still use a Raspberry Pi 3 as the 'brain' for the Mk 2 version, should make for a somewhat sleeker machine.

robertojones - 2019-01-14 11:54 AM

I finished assembling the machine over the weekend, just a few fit and finish issues to sort and the power management to work out (a bit of Python programming).

I've typed this post on my new device. Photo below, as you can see it could use some tidying up but so far I'm reasonably happy with it. Already working on the design for Mk 2 ( slimmed down version), though I think I'll sort out the usability gremlins with this one before I start building anything.