Videos: I forgot which way I soldered the chip!

I was soldering a QFN-25 in flip-chip configuration and forgot which way round I soldered it… Here’s how I figured it out.

HP2VGA: PCB Design with a BGA

This PCB represents two firsts for me – first 4 layer board and first BGA package. The former isn’t really a big deal and is really just necessary because of the latter. Due to my memory requirements, I was forced to use the Lattice iCE40HX8k which has more RAM than the smaller variant, iCE40HX4k, and also only comes in BGA packages.

Continue reading “HP2VGA: PCB Design with a BGA”

Project: PCB Mill CNC – Built

It’s been a long time since I last posted. The last couple of months have consisted mainly of work, holidays and back-to-uni chaos. Nonetheless, I have found time to work on the CNC. In fact the majority of the mechanics AND electronics have been done.

The current design has not strayed far from the original plan. There have been a few minor changes including adding extra spacers and changing the shape of brackets but nothing too interesting.

The largely finished mill!

The largely finished mill!

All of the electronics are tucked away inside a standard project enclosure into which I drilled a hole for the parallel port and a hole for the power and motor connections.

The electronics are hidden away showing only a parallel port and a tangle of wires for the motors and power. Shame about the tape!

The electronics are hidden away showing only a parallel port and a tangle of wires for the motors and power. Shame about the tape!

Remaining tasks:

-Add a support bracket connecting the horizontal aluminium to the vertical aluminium to minimise wobbling of the drill.

-Properly attach the electronics to the body with bolts rather than tape.

-Insert proper power supply plug and buy power supply


Unfortunately, with the exception of the last one, none of these tasks can easily be done while I am at university due to lack of tools (although as an engineering student I probably could if I tried hard enough).

Fortunately, none of them seem particularly important as current results look promising and these will merely be icing on the cake.

Yesterday, for initial testing I put a pencil lead into the drill and set it drawing Road Runner on a piece of paper. After a little while the lead fell out (drills aren’t made for this 😦 ), but what it managed to do looked promising.

You can make out Road Runner's wing!

You can make out Road Runner’s wing!

Today I put a 1mm end mill into the drill and set it spinning at 8000rpm. Rather than let the CNC loose, I controlled it myself using the arrow keys to direct the drill over some copper clad board.

Copper clad board with some random copper etched away!

Copper clad board with some random copper etched away!

As you can see, the copper removed nicely, if not a little deep, and left sharp edges. In fact the drill cut through the copper with no stutter at all so I am confident it will be up to the job. I am looking to order some finer end mills, maybe 0.1mm so that I can etch useful circuits!

Hopefully the next post will be sooner.

Project: Smart Watch – Disaster (I thought)

Today was pretty productive; I now have more or less functioning straps – there will be a detailed post on this soon – but the aim of the post is to describe a disaster that (I hope) I managed to avert.

I was working on installing buttons in the case so that the electronic switches could be pressed from the outside. First thing’s first, I need to drill some holes… The lid comes unglued, the drill slips, the lid is ruined. Not a big deal – I have plenty of plastic and it only takes a minute to cut.

This time I drilled the holes before gluing the lid on – success.

Now lets put the circuitry back in – it doesn’t fit.

Confusion. Scrape away the glue from the edges. Okay, it fits.

Right, so lets take the circuitry out and put the buttons in the holes. Damn fiddly, but fine.

Now to replace the circuitry… A switch catches on the button and comes clean off the circuit board.

Hair torn out.

Test other buttons with new program. First button – fine. Second button – fine. Third button – fallen off. Fourth button – doesn’t work.

More hair torn out.

By repeatedly reheating the joints of the non-functioning button and adding a little more solder the button seems to work 85% of the time. Okay, that’ll do for now.

Soldering on the fallen-off-button – turns out to be a piece of cake. Can I have my hair back?

Project: Smart Watch – Batteries

Having been let down by my original battery supplier (they never arrived from the Philippines) I ordered new ones from Cool Components on the weekend, this time 2x110mAh 3.7v LiPo cells. Impressively, they arrived today and they are much smaller than I thought!


Definitely going to fit two of these on my wrist 🙂

Now I just need to order some JST connectors to wire them up in series and get some leather to make a strap!

Project: Smart Watch – Case First Attempt Part 2

I like to think today has been pretty productive. Major advances on the case have been made to the extent that it can now be strapped to my wrist. 20140720_20221820140720_202225 Clearly there is no power the the watch, because the strap is only temporary and doesn’t contain a battery. Furthermore, the buttons are covered by a layer of plastic and cannot be pressed (more on this in another post). However, I am happy with the shape of it and am confident it can be progressed. The case consists of only two parts which will (probably) be held together with a rubber band.

Structure of the case

Structure of the case

The next step will be to drill holes for the power wires and also attach velcro for the strap.