A nerd snipe, in which I learn to read gerber files

So, I had the realisation last night that the biggest sunk cost with getting a PCB made in China is the shipping. The boards are about 50 cents each, and then its $25 for shipping (US dollars of course). I should therefore be packing as many boards into a single order as possible to reduce the shipping cost per board.

I have a couple of boards on the trot at the moment, my RFID attendance tracker project (called GangScan), and I’ve just decided to actually get my numitrons working and whipped up a quick break out board for those. You’ll see more about that one later I’m sure.

I decided to ask my friends in Canberra if they needed any boards made, and one friend presented with a set of Gerber CAM files and nothing else. That’s a pain because I need to know the dimensions of the board for the quoting system. Of course, I couldn’t find a tool to do extract that for me with a couple of minutes of Googling, so… I decided to just learn to read the file format.

Gerber is well specified, with a quite nice specification available online. So it wasn’t too hard to dig out the dimensions layer from the zipped gerber files and then do this:

Contents of file Meaning Dimensional impact
G04 DipTrace 3.3.1.2* Comment
G04 BoardOutline.gbr* Comment
%MOIN*% File is in inch units
G04 #@! TF.FileFunction,Profile* Comment
G04 #@! TF.Part,Single* Comment
%ADD11C,0.005512*% Defines an apperture. D11 is a circle with diameter 0.005512 inches
%FSLAX26Y26*% Resolution is 2.6, i.e. there are 2 integer places and 6 decimal places
G04* Comment
G70* Historic way of setting units to inches
G90* Historic way of setting coordinates to absolute notation
G75* Sets quadrant mode graphics state parameter to ‘multi quadrant’
G01* Sets interpolation mode graphics state parameter to ‘linear interpolation’
G04 BoardOutline* Comment
%LPD*% Sets the object polarity to dark
X394016Y394016D2* Set current point to 0.394016, 0.394016 (in inches) Top left is 0.394016, 0.394016 inches
D11* Draw the previously defined tiny circle
Y1194016D1* Draw a vertical line to 1.194016 inches Board is 1.194016 inches tall
X1931366Y1194358D1* Draw a line to 1.931366, 1.194358 inches
Board is 1.931366 inches wide (and not totally square)
Y394358D1* Draw a vertical line to 0.394358 inches
X394016Y394016D1* Draw a line to 0.394016, 0.394016 inches
M02* End of file

So this board is effectively 3cm by 5cm.

A nice little nerd snipe to get the morning going.

Gangscan 0.6 boards

So I’ve been pottering away for a while working on getting the next version of the gang scan boards working. These ones are much nicer: thicker tracks for signals, better labelling, support for a lipo battery charge circuit, a prototype audio circuit, and some LEDs to indicate status. I had them fabbed at the same place as last time, although the service was much faster this time around.

A gang scan 0.6 board

I haven’t got as far as assembling a board yet — I need to get some wire thin enough for the vias before I can do that. I’ll let you know how I go though.

Trail run: Tuggeranong Stone Wall loop

The Tuggeranong Stone wall is a 140 year old boundary between to former stations. Its also a nice downhill start to a trail run. This loop involves starting at the Hyperdome, following the wall down, and the continuing along to Pine Island before returning. Partially shaded, and with facilities at the Hyperdome and Pine Island. 6km, and 68m vertically.

Trail run: Lake Tuggeranong to Kambah Pool (return)

This wasn’t the run I’d planned for this day, but here we are. This runs along the Centenary Trail between Kambah Pool and Lake Tuggeranong. Partially shaded, but also on the quite side of the ridge line where you can’t tell that you’re near the city. Don’t take the tempting river ford, there is a bridge a little further downstream! 14.11km and 296 vertical ascent.

Be careful of mountain bikers on this popular piece of single track. You’re allowed to run here, but some cyclists don’t leave much time to notice other track users.

Trail run: Barnes and ridgeline

A first attempt at running to Barnes and Brett trigs, this didn’t work out quite as well as I’d expected (I ran out of time before I’d hit Brett trig). The area wasn’t as steep as I’d expected, being mostly rolling grazing land with fire trails. Lots of gates and now facilities, but stunning views of southern Canberra from the ridgeline. 11.11km and 421m of vertical ascent.

Trail run: Pine Island South to Point Hut with a Hill

This one is probably a little bit less useful to others, as the loop includes a bit more of the suburb than is normal. That said, you could turn this into a suburb avoiding loop quite easily. A nice 11.88km run with a hill climb at the end. A total ascent of 119 metres. There isn’t much shade along the run, but there is some in patches. There are bathrooms at Point Hut and Pine Island.

Be careful of mountain bikers on this popular piece of single track. You’re allowed to run here, but some cyclists don’t leave much time to notice other track users.

Trail running guide: Tuggeranong

I’ve been running on trails more recently (I’m super bored with roads and bike paths), but running on trails makes load management harder — often I’m looking for a run of approximately XX length with no more than YY vertical ascent. So I was thinking, maybe I should just write the runs that I do down so that over time I create a menu of options for when I need them.

This page documents my Tuggeranong runs.

NameDistance (km)Vertical Ascent (m)NotesPosts
Cooleman Ridge9.78264Cooleman and Arawang Trigs. Not a lot of shade and no facilities.25 April 2019
Pine Island South to Point Hut with a Hill11.88119A nice Point Hut and Pine Island loop with a hill climb at the end. Toilets at Point Hut and Pine Island. Not a lot of shade. Beware of mountain bikes!21 February 2019
Barnes and ridgeline11.11421Not a lot of shade and no facilities, but stunning views of southern Canberra.2 May 2019
Lake Tuggeranong to Kambah Pool (return)14.11296Partial shade and great views, but beware the mountain bikes!11 May 2019
Tuggeranong Stone Wall loop668Partial shade and facilities at the Hyperdome and Pine Island.27 April 2019

Trail run: Cooleman Ridge

This run includes Cooleman and Arawang trig points. Not a lot of shade, but a pleasant run. 9.86km and 264m of vertical ascent.