2nd December 2013
Haven’t done any more on the engine lights but have managed to get quite a bit of other stuff done…
Over the weekend I actually managed to do some glueing and painting! I couldn’t believe it, not sanding, not wiring, not filling and sanding, not researching frikkin paint tones – actual painting and glueing! And here it is.
Ok it isn’t much, but enjoyed every last press of the airbrush button, each whiff of thinners and each dab of glue. Ah, I remember when modelling was all glue and paint – none of this attention to detail nonsense – still I digress 😉
Back to the sanding and wiring…
By the way, the sensor above was painted with Tamiya Copper XF-6. It looks much better in real life though, I just couldn’t get my phone camera to get the copper to look right.
I started lighting the saucer, to do the main lighting of the windows I’m using a 1m strip of warm white LEDs that I procured on eBay. These run off 12V DC and you can cut them into sections of 3 LEDs as below:
The LED strips (I bought weatherproof ones in error) have a heavy clear coating which needs to be removed before you can solder wires onto the sections. The easiest way I found to do this was to cut through the clear coating with a scalpel and a sawing action being careful not to cut all the way through!
You can then peel off the unwanted coating with a thumb nail to reveal the copper contacts.
The contacts accept solder nicely and have no problem in wetting, though too much heat can melt the bottom of the strip of LEDs to your cutting mat *ahem*…
For each section of windows, I’m aiming to have a strip of LEDs near by to illuminate the window. Although the strips of LED have self adhesive tape on the back of them, I’m not trusting this and am hot glueing each one in using a hot glue gun:
The saucer also needs 4 round LEDs fitting – these are also held in place with hot glue:
The round LEDs are 3mm diameter and are a perfect fit in the holes provided:
Once the lights has been installed, it was time to fit all the clear parts. This is where the sanding kicked in again 😉 The clear parts are a really tight fit in the holes, especially when the holes have overspray in them, so each window on each clear part had to have its sides sanded or shaved to get it to fit all the way in.
For some of the clear parts it was easier to cut them into sections and fit them bit by bit instead of trying to fit a whole clear panel at once.
Also the clear parts had to have their inside faces opaqued up using 280 grit so as to diffuse the light. This took a lot of time as each and every square pane had a sink mark in it that took quite a lot of sanding to remove.
But once the windows had all been sanded they could be fixed in place with clear PVA. Being careful not to get any PVA on the nicely opaque inside surfaces as we don’t want to turn them clear again 😉
To help keep the wiring (relatively) tidy, where I’ve used a pair of wires I’ve done them as a twisted pair. The easiest way to do this is to tie the ends of both wired together with a good old half-hitch:
Stick the half hitch into the jaws of a pin vice (or cordless drill if you’re feeling manly)…
Grab a turn around your finger and twist the pin vice. You can leave as much length of wire between finger and pin vice as you need – 18″ is probably a useful amount to do in one go. If you want to do longer lengths you can use a cordless drill and stick the free end in a bench vice or tied around a nail.
Once it’s twisted fairly tight, give it a small stretch to set it and there you go…
I’m going to end up with quite a few wires coming out of this model all going to various microcontroller I/O channels so I took the liberty of making and printing a basic wiring schedule to help me keep track of what goes where… I also found a handy bag of cable idents in my hoard of useful bits that I know will come in useful one day…
The cable idents are just small lengths of PVC tube, colour coded according to resistor colour codes (Black=0, Brown = 1, Red = 2 etc…) and they also have the number printed on them in case you don’t know your resistor colour codes off by heart. The ones I have are way too big for the wire I’m using so I chose to mark the end of each wire by tying the cable ident in with a half hitch…
The other end of the wire is soldered to the relevant LED inside the model, and the idented tails will come out of the base of the model when all closed up. The numbered idents will tell me which wire is connected to which destination when doing the final wiring.
You can just as easily use small bits of masking tape and write on the cable numbers, but they can tend to get stuck to each other/fall off if you’re not careful.
And here we are with the saucer wiring, lighting and glass in place and wired into the micro controller ready to test:
The microcontroller is an Arduino Nano and is an amazing bit of kit. It has 14 digital input/output pins as standard and 6 of these can be driven as analogue outputs (PWM) to allow for fading of LEDs / motor control etc…
Here I’ve got the Arduino plugged into a small breadboard that allows you to easily plug in wires and resitors without having to solder them together. This is ideal for prototying as you simply push the wires into the holes.
Once the circuit has been finally worked out, the breadboard will be removed, and the microcontroller will be fitted in the base of the model, and the required resistors will be permanently soldered onto Veroboard.
And now the moment of truth, the lid has been dry fitted and everything is powered up and ready to go:
I’m really happy with the way the lighting has turned out so far. I still need to tweak a few windows here and there, some of them need a little dimming down which you can’t see in the photos…
Also the lid will need to be glued down when I’m happy with it all, and then filled and painted. But a small amount of localised touching in will sort that.
The nav lights are flashing courtesy of the microcontroller so until next time I’ll leave you with a short video of the illuminated saucer complete with flashing lights