2009-05-31
May 2009 Trash and Treasure
Various other commitments have kept me from the last few ARNSW meetings, it was nice to visit again. Peter was nice enough to provide transport to the Dural site. The weather was unfortunately appalling, cold and rainy the entire day, and I had dressed inappropriately for the conditions but a good time was still had.
The most obvious change at the site is the new shed. After so long it is great to see it finally erected. The inspection certifying it for public access hasn't occurred yet, so the meeting was held under its veranda. The sound of the rainwater falling from the top-level roof down-spout to the veranda awning was at times quite deafening, and had that annoying "chaotic attractor" cadence where interval and amplitude are related but still random enough to really drive you up the wall... I found it quite maddening truth be told, especially combined with the frigid temperatures, but the quality of the PCB lecture made it worthwhile.
The trash and treasure was unfortunately familiar. All the same junque that you've seen over and over again... I think I've picked clean just about all sources of interesting stuff. Same goes for suppliers, Rockby, Vanbar, even eBay is looking pretty grim of late. I hope this is just an indication of my current phase of geeky jadedness, not a true reflection of the future state of affairs on the surplus market! I tend to go through phases of loosing my mojo for building stuff, this is just yet another I suspect. On the ferry ride to work I often sketch ideas for projects, but of late nothing but the horror of the blank page has been my commute companion. Is this burn-out? In my opinion desire deprivation is the root of most depression, affective or creative in nature... Maybe its just the weather, seasonal muse holidays?
BBQed sausage sandwitches and geeky chatter filled the time until the Homebrew Meeting started in earnest.
As usual we began with Show and Tell. (I presented Charles Wenzel's nuclear war detector.) Stephen showed us a very nice transceiver built into an old commercial radio case.
Peter showed us a prototype enclosure for a large project made using MDF as a template for a later Aluminium version. He also passed around his new "filing irons" made to Drew Diamond's specs.
Graham showed us his new stainless steel rope dipole with centre insulator/balun assembly.
The meeting then moved onto the lecture of the day; various methods of PCB fabrication. John began with a demonstration of how he makes his quick prototype boards.
Then Peter continued with a discussion of etching methods; Ferric Chloride vrs Ammonium Persulfate, temperature control, agitation, etc. He also passed around some sample boards, including one very interesting example of a milled board made using an engraving machine.
Mike finished with an excellent step-by-step presentation on photo-lithographic techniques to make very high quality boards suitable for modern high density surface-mount designs. He discussed mask registration techniques, exposure control, resist development, etching, resist stripping and tinning the resulting board. His exposure box using UV LEDs was quite interesting, he regulates the current to control the exposure for optimal masking.
Other very practical ideas from Mike included little stand-offs made from notched PCB scrap and an L-shaped square of PCB material used to assist with registration. I was very impressed with the quality of the lecture. It is always a treat to see people talk passionately and practically about something they have real-world experience with.
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