Fernvale is a modular open hardware development platform for the Mediatek MT6260 SoC, featuring a keypad, screen and SIM socket etc. — all the basic things you'd expect with a mobile phone — plus plenty of debugging interfaces.
The case we've developed is laser cut from 3mm glass look and 5mm grey acrylic, and provides a neat solution to securing the various components once connected, offering some degree of physical protection while retaining all import access to headers.
Design for laser cutting is a pleasant introduction to CAD for a number of reasons. There are many software packages that can be used to generate the correct type of design files including some that may be familiar - such as Adobe Illustrator or Inkscape - from other design practice. Modern desktop laser cutters tend to use vector files containing paths that are simple to generate and edit with lots of tutorials available online. It is possible to be designing and making physical things within hours.
When designing for laser cutting one tends not to take the width of the laser beam into account - meaning that a relatively complicated step used in more traditional CNC machining - toolpath generation - can be ignored. The toolpath of a job is the path through space that the tip of a cutting tool follows to produce the desired workpiece.
Imagine a CNC milling machine: it uses cutting tools similar to drill bits to cut away material. These tools have a diameter that must be taken into account when calculating the toolpath. Say we want to cut out a circle of 50mm diameter from a sheet of MDF using a 6mm milling bit. If we draw a 50mm circle in our design software and export that as our toolpath the milling machine will follow the toolpath and cut out a 44mm circle.
If a 6mm milling bit follows a path it will cut out a 6mm groove along said path. This results in 3mm extra cut from the inside and outside of the path. See Figure 1 below.
Figure 1 - cutting with a 6mm milling bit
By generating a toolpath we can resolve this problem and cut out a workpiece of desired size. See Figure 2.
Figure 2 - following a toolpath with a 6mm milling bit
Milling bits need to be substantial enough to cut through material - it is possible to buy bits with a very small diameter but these have drawbacks: they are delicate, break easily and cannot cut material very quickly. Laser cutters cut sheet material with a focused laser beam rather than a milling bit. This beam can be very small (high quality machines down to 0.1mm or smaller, cheaper machines up to 0.5mm or larger).
Figure 3 - cutting with a focussed laser beam
Comparing Figure 1 and Figure 3 highlights the difference between the outputs from a laser cutter and milling machine without extra toolpath generation. For much of the design work we currently do (cases for electronics projects, jigs, tool holders, tools for our workshop, signs etc) we do not need 100% accuracy to within thousandths of a mm. If we were building engines or rockets with very high tolerances we would need a much higher level of accuracy, generating toolpaths from design files and we would hope to be using very expensive tools and machines!
The width of the laser beam in a relatively low cost desktop machine is not negligible - in fact we can use it to our advantage as shown in Figure 4 below.
Figure 4 - using the width of the laser beam to our advantage
The above is often overlooked when designing for laser cutting and simply taken for granted. Some may argue that not generating toolpaths is poor engineering. Ignoring the above information and not wanting to understand may indeed be poor engineering practice but this is up to the individual maker, engineer or designer to decide.
For our needs we can continue to use our design files as toolpaths and produce good usable results for both rapid prototyping and manufacturing physical things. If we wanted to mill out the above parts using a CNC milling machine we would have to use a more complicated work flow with additional steps - something we will cover in later posts.
References + further reading
- laser information: http://www.parallax-tech.com/faq.htm
- toolpath definition: https://www.wordnik.com/words/toolpath
We found that when using our Novena all-in-one desktop with computationally intensive workloads, the Freescale SoC would quickly heat up and the CPU governor would then kick in and throttle back the clock speed. This isn't so much of an issue with tasks such as compiling software, however, it can pose a major problem when running software-defined radio (SDR) applications that simply will not work at reduced processor speeds.
Thankfully we managed to source an ultra-slim micro fan that can be affixed above the SoC and powered via the front panel PCB. We've made a small batch of kits that comprise of the fan mounted in a laser cut acrylic holder and with a power cable terminating in the appropriate JST connector. This assembly is secured in place via two M2.5 hex standoffs, which are themselves fastened to the enclosure via two conveniently placed threaded inserts.
Once these are sold it's not clear that we will produce any more, as the fans are not easy to source — some sold as the same part are almost identical but half the power and do not move sufficient air — and for something that is very simple, assembly ended up being quite time consuming.
Those who follow Boldport on Twitter will know that the correct answer to the question, "which particular type of tea powers Boldport's design work with PCBmodeE?", is of course Russian caravan!
Thanks to all those who entered the competition, a correct entry was selected at random and congratulations go to Lily Madar, who is the winner and a package will be heading her way this week.
It's no secret that we're huge fans of Boldport's work and it turns out that their excellent taste extends beyond the design of beautiful, functional circuits, to that very best of beverages, tea.
Which brings us to the subject of this competition: can you tell us which particular type of tea powers Boldport's design work with PCBmodeE? If you think you have the answer drop us a line via email@example.com. You have until 22nd May 2015 to enter, a single correct entry will be selected at random and the winner will be announced on 29th May 2015.
And the prize? A selection of Boldport designed open source hardware goodness, of course. Shipped to anywhere in the world at our cost.
The prize package will include a Cuttlefish kit. A minimal Arduino-compatible board inspired by the Shrimp, the Cuttlefish is a simple but fun design that was commissioned by Embecosm for use in outreach workshops. A CP2102 USB UART will also be included for programming.
We'll also include a couple of very special limited edition kits that were put together for Open Source Hardware Camp 2013 and 2014, and packaged by our friends at Oomlout.
The first of these is the Wuther board, a Bordport redesign of Ihsan Kehribar's excellent USB multi-tool, littleWire. The second is the Nutclough, a portable audio amplifier with a design that was commissioned by Calrec Audio — makers of breathtakingly beautiful and blisteringly high performance broadcast audio consoles — to celebrate their 50th anniversary.
The Wuther board is not available to buy and the only other chance you have of getting your hands on a Nutclough kit is if you bump into Calrec at a trade show and speak nicely to them. Of course, both designs are open source and so you're free (and encouraged!) to make your own PCBs.
Finally, we will include a Pease board — Boldport's tribute to the late, great Bob Pease. This is the PCB only and no components are included, but the board does also double as a key ring and what engineer wouldn't be proud to carry this around in their pocket.
Terms and conditions
Please see the Terms and Conditions page.
We've just added a new case kit to the store which is designed to accommodate the Novena open hardware computing platform mainboard together with the companion Myriad-RF SDR module. Features include:
- U.FL to panel mounted SMA connector cables for TX and RX
- Cut-outs for access to FPGA JTAG and UART headers
- Array of M3 mounting holes with "Peek" compatible spacing
- High quality ebm-papst DC fan with additional decoupling
- Mountings for a 2.5" HDD/SSD
- FPGA heatsink
- Labelled ports
A full bill of materials, together with assembly instructions and the design files, can be found on GitHub.
Note that we also have a limited number of Novena-RF modules available.
Detail of Harrison L5A Gap Bed Lathe
Welcome to the Ground Electronics blog, which we will be using to provide details of new products and sneak previews of some of those in development, along with notes on workshop techniques and insights into our adventures in manufacturing!