Build Log: Part 6
It’s been a while since I updated this, my apologies to everyone for my tardiness…here’s the news!
I am intending to have some “action” lights on the floor of the shuttle bay, basically running lights that indicate “takeoff” to be ready. To accomplish this, I need a timer circuit and a set of lights to strobe properly. LEDs make best sense, and I know someone out there has lots of these sorts of circuits, so I went hunting for a little kit to do the job. I found a small electronics assembly kit of six chaser lights using red LEDs and a potentiometer that is used to control how fast the chaser works. (For those who are interested, it’s this one: https://www.conrad.de/de/conrad-6-kanal-led-lauflicht-190128-bausatz-6-15-vdc-190128.html – very clear instructions, easy to build).
I first assembled the chaser board. After opening up the kit, I arranged the parts in order of their mention in the instructions (they’re labeled there as “R1”, “R2”, etc. for resistors, “K1” etc. for capacitors, and so on). By poking them into a spare piece of foam I kept them handy and kept them from rolling away out of sight.
I find it useful to keep the master diagram right in front of me while I’m working to be a fast-glance reference of what I’m doing. The board itself also was marked with appropriate labels, but it helps to have the written diagram since some of the elements are polarized and only work one way (cylindrical capacitors and LEDs being particularly notable in that regard).
The legs on most components are too long once the part is inserted, so once they’re in and soldered securely, snip off the excess. Meanwhile, those “legs” are very useful in keeping the element in place – once you insert the legs and get the part into proper position, you can stretch the legs out to get a friction grab on the board and hold it in place while you solder it.
I find a temp of 350C to be ideal for soldering, as it melts solder really fast as well as heats the parts up properly very quickly – so I can get the job done quickly, and heat won’t transfer too far through the parts from me holding the tip against them for too long. If yours doesn’t have a temp control, don’t worry about it, chances are it’s quite hot enough.
For those of you who haven’t soldered before, here’s the basics of what you’ll need:
- A soldering iron or pen (I find the pen models a lot easier to use, the “gun” ones don’t
give me the precise control I like to have). The lowest priced ones of these are $10-$15 at Radio Shack or online. Some very fancy workstations can run $100 or more.
- Resin-core solder (you could get some that doesn’t have a resin-core and use a pack of flux instead, but I find resin-core a lot more convenient). This basically does a job of cleaning the parts while soldering them. Less than $2, generally.
- A drop-cloth or surface you can set under your operation (a couple sheets of office paper works fine, too).
- A wet kitchen sponge or soldering sponge (most irons come with one attached to the holder)
- “Helping Hands” – a cheap pair of alligator clips mounted on an adjustable bar, usually with a magnifying glass. You can get one of these for $5-$10 on ebay or something.
The process goes like this – turn on the iron. Let it get hot enough to sizzle the sponge (fancier electronic stations have temp readouts). You position the parts/board in the proper place and secure them so they don’t drift around (usually you can ‘friction-fit’ them together well enough for the purpose), and mount them in the Helping Hands unit so you can get at them easy. Once they’re ready, get a string of solder
in your off-hand, and with your primary hand, place the tip of the iron against where the parts/board meet. Immediately hold the tip of the solder against the parts.
After a few seconds, the parts will heat up enough to melt the solder, and it should flow easily. You want to cover the surface of both the part and the board, ensuring that you have a solid bond between them and that the solder establishes a clean connection between them. Don’t use so much that you end up with a big glob on the connection, just use enough that you’ve got a silver surface on it. It should end up looking like water sticking to things, where it “climbs” he part a little bit.
You don’t want to overspill the connection, either, as that might touch another connection and cause a short (at best this would result in your board malfunctioning, at worst it’ll burn your board out completely when you put power on it).
When soldering, clean the tip (using a wet kitchen sponge is fine if you don’t have any
specific items for this purpose) between every use by dragging it across the cleaning surface. It’ll sizzle and leave tiny nuggets of solder that can be disposed of later. When the tip is shiny it’s clean. You don’t want to be using a tip that is caked up with slag when you’re trying to do precision work.
Also – when you are soldering cables or wires, it is very helpful to “tin” the ends of them before connecting them where they belong. What this means is to strip a short section (.5cm, or maybe 1/8 inch) bare, and then heating it up with the iron and applying solder to the end so that it takes on a coating of silvery solder. This burns off any residues that might be clinging to the surface and also coats it with low-melting-point clean solder that will merge with the other part and the solder you are applying, making the connection a lot quicker to accomplish.
So, the board got built, I tested it and adjusted the speed of the chaser to where I was happy with it. (Remember, I’m only going to get to set it once, it’ll be embedded in the engineering hull under the floor of the shuttle bay when I’m done.) I painted the LEDs with clear gloss acrylic to shield them and also to prevent frost “ghosting” happening when I glue strands to them.
I then took the floor of the shuttle bay, and measured spacing about 3mm to either side of the yellow center line of the bay. I marked off six spots on each side, 1cm from each other, and drilled them out with a .5mm pin-vice (I also managed to scratch the floor of the bay, which resulted in a long and painful repair process).
In the bottom of the engineering hull there’s a perfect spot to mount it, right up against a bulkhead beneath the bay. I opened up a pair of gaps so I could slip the power wires into the forward compartment when the board is mounted. Based on this location, there’s going to be about 12cm of space between the LEDs and the holes that correspond to them in the bay floor. (Image later, once I start the mounting.)
I cut 13 lengths of .5mm poly fibre optic strand of 15cm each. The extra one is for something special I’ll tell you about when I get it working (plus in case I screw it up I’ll have a spare). Each one of these I then “tapped” an end against the soldering iron, producing a small, flat “nail-head” surface.
Using cyanoacrylate (CA) super-glue, I then glued two strands of fiber to each of the six LEDs towards their top, where they are brightest (this is important, if you glue them too low they won’t pick up a lot of light and might be easily missed). The “nail-head” end is what makes this easier, since it gives a larger surface to grip against the LED. I didn’t have any zip-kicker available, or I would have tried that. I wasn’t really certain if that would have caused the CA to frost up, so it’s probably best I didn’t have any. This use of CA glue is why I painted the LEDs with gloss clear acrylic earlier – CA tends to cause plastics and glass to “frost” over from humidity or softening of the surface, but a gloss acrylic won’t suffer from this.
Once the CA was thoroughly dry, I applied a hot-glue glob to each LED, covering the CA and reinforcing it. I’ll later paint black over these to prevent light leakage and keep the chaser lights isolated to only the fiber strands.
I have not yet affixed the board to the bay floor, but what’s going to happen there is I’ll feed the fiber strands up through the floor with a few millimeters extending above the floor and glue them in place there. Once the glue dries, I’ll shave the protruding ends of the strands with a razor knife in a fashion very similar to how one shaves a skin of hair. At that point, we’ll have sequenced running lights strobing in a “takeoff” pattern.
That’s it for now. I’ll update again, hopefully a lot sooner than the frequency between this update and my last.