Arduino Control Box: a Step by Step Guide – Part 5 – Drilling time!

Part V of the guide, we’re almost there: the wiring diagram is ready, we have our buttons and encoders and we have our box. Before starting the assembling phase, let’s review some of the tools that might come handy.

Drill driver: I have an old DeWalt cordless drill driver, it holds drill bits max Ø10mm. It does the job.
Drill bits: I used to build model for WH40k years ago and I have a 1-5mm set. I have bought another cheap set, max Ø10mm. I recommend two sizes: a small one, to prepare a guide for wider holes (2-3mm will do, whatever you have in your garage). Most of the smaller buttons I have found have a diameter of 5-6mm so a second drill bit of that size will come handy.
Cone drill bits: I have bought a cheap set only recently and damn, they make your life so much easier. Since we will be working mostly with plastic, even quite cheap sets work like a charm.
Countersink drill bit: optional. Before buying the Cone bits I used this tool to make holes wide enough to host some particularly wide buttons. It comes handy when dealing with unusual diameters or to “clean” the hole instead of using sandpaper.
Caliper: the real man best friend 🙂 Simply a must have; you need one.
Thin permanent marker: you can decided to either mark the points to drill with a marker or cut them into the plastic. It’s up to you, I personally do both.
Multimeter: a must have for debugging the wiring. Unless you have done everything perfectly and I bow to you 🙂

Mirror mirror

IMPORTANT! We will drill on the internal part of the enclosure. Therefore, when planning and defining the position of the holes, remember that our wiring diagram is the specular image of what we actually need.
The easiest solution is to paste the image in GIMP and flip it.

Marking time

Get the wiring diagram on your PC and calculate the distances between the borders or the box and the centre of the buttons. I’ve found that drawing a reference matrix is actually easier. If you are using LibreOffice Draw, this operation will take just a few minutes and will be also very precise if you have draw your components and the box in 1:1 scale.

Now get the cover of the enclosure and the calipre. Measure the distances between the borders of the box, both vertically and horizontally and mark the points where your components will be placed with the marker. Proceed until every button of your UFC has is respective dot on the cover. For sake of clarity and to avoid confusion, you can write the expected diameter of every hole near every reference dot.

This is a detail of my Auxiliary Box. As you can see, the marks and cuts are clearly visible inside the enclosure cover (green arrows).

SbS_5-enclosure-cover-cuts
Reference marks and cuts inside the enclosure cover

Once every reference is marked, it’s time to start drilling. I usually start with a drill bit of very small diameter, then enlarge it depending on the final diameter required. This is a fairly quick operation, assuming every button is Ø12mm, you can start with the 2mm drill, check that the hole is exactly where you want it then use any other drill to make the hole wider enough to use the Cone drill bit. The Cone drill bit cuts throught the plastic very easily so pay attention and avoid making an excessively large hole.

When everything is done, get your buttons and encoders, place them in their slots and clamp screws and nuts and check the result.
SbS_5-bolts-and-nuts
Don’t put the encoders knobs in place, you risk unnecessary scratches.

Some buttons won’t be perfectly aligned but remember we are not using a CNC or any very precise tool. Small errors and imperfections might occur.

The manual part is almost over. Next step is soldering and then, finally, my favourite part: coding!

PS: it may sounds taken for granted but remeber to drill a hole for the USB cable 🙂

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