I imagined the Falke to be a craft which has an anti-gravity unit to lift itself and used some kind of jet system for propulsion. So, the twin booms must the jet engine’s intakes at the front. This makes the Falke function like a VTOL aircraft! Alas, the type of jet fan I am looking for does not exist unless I can make it from scratch with metal, which it is impossible for me. Think of a music box’s metal tube but with extended long fins, slowly spinning…
The idea was for the fan blades to spin slowly and its blade movement highlighted from a LED. Unfortunately, this would mean customizing a circuit to control the fan’s speed as the computer fan was spinning too fast.
Then another idea came to me which is to use LEDs to simulate the fan blade movement. The observer does not necessarily need to see the actual blade and so, its spinning ‘movement’ would complete the illusion! The LEDs will be long rectangular, to represent the long fan blades. Because the idea is to create the illusion of the blades spinning with lighting from the back. If the mechanical fan was a go, it would be backlit by a courtesy light (SMD) LEDs.
This is the ‘cage’ to block most details of the turbine. This came in the form of a car USB charger, where the ‘cage’ is made from aluminum. The shop, Mr. DIY has them in several colours but I chose the non-coloured version since I do not know how to remove the plating. It has the right size and fits into the Falke with not much issue.Here are the pieces after being dismantled. I only need the Aluminum piece and also the white plastic.
Mounting SMD LEDs in the square holes will only create the illusion of some axially rotating Sci-Fi engine. Also, it is possible that in the long run, aluminum might touch the wires and create shorts, which is not a great idea.The plastic part is cut in half with the domed part thrown away. The remaining piece is important as it has the slits to hold the aluminum cage.Because the Falke’s front has a removable panel on its side, the plastic is cut to match the shape of that ‘missing’ panel’. After the cut, the part on the left is thrown away. The remaining piece will act as the holder to the aluminum and also as a light reflector for the LEDs. You can put an aluminum sticker to reflect the light more, but it’s too bright already in there.This is how the assembly looks like (the opening is facing downwards and to the left). The whole assembly is facing the front, towards you.There is a part in the water filter which has almost the right size for the UBS charger to lock into. Using thin cement, I glued the part exactly in the middle. This ‘ring’ will lock one end of the aluminum cage into place.
See the small little 3mm hole there? It is for the Falke’s front spotlight using 3mm LEDs. It’s a good idea to prepare/drill this hole now so that you would not be obstructed later on when the intake has been mounted.Test fitting of the whole assembly before finalizing it with glue. Note the insides of the fuselage has been sprayed with Mr. Color #116 RLM66 Black Gray. I want to standardize the Falke’s interior colour with this shade.
Note the alignment of the cage’s fins. At least three of them must line up to the centre of the fuselage’s line. Later on, they are used as ‘alignment’ slots to hold up the scratch-build styrene bar.
In the next segment, I will show you how I construct a non-moving turbine fan for the aluminum cage. It will involve modifying an off-the-shelf circuit and some very unconventional soldering. And to most, it will be quite technical too.
THE INTAKE: ELECTRONIC FAN BLADE
In this article, I would attempt to explain my challenge of having a spinning fan blade inside the intakes of the Falke. Originally, I wanted to construct a jet turbine-like assembly and then use a slow spinning motor to spin it. This idea was discarded once I realised I could not create those thin jet turbine blades in exact measurement. Plus, over time, the glue/cement might fail which leads to the blade falling off. So, a metal casting would work but the cost is insane. Even if I got it to work, the power needed to run off the noisy planetary motor would be quite substantial.
The alternative would be to use LEDs to give the illusion of a backlit rotating fan blades. The electronics involved would be off-the-shelf solutions which not only saves time and cost, it also proves that this solution does the job equally as well compared to programming a microcontroller. Just to recap, the LEDs used would be long rectangular white SMDs; not the 2mm x 5mm x 7mm types nor the conventional 3mm or 5mm round ones. So, the lucky 7020 (7.0mm x 2.0mm) SMD white LED fits the bill as it has the length to make the ‘fan blades’. But oh, it is so bright!
Before we start, you will need the following tools: 1. A 30W soldering iron with a pencil tip 2. 60/40 solder with a 0.5mm or 0.8mm diameter 3. Solder Flux (I call them solder flux here but some might call them solder paste. They are orangy clear and not greyish silver) 4. Double-sided tape, preferable those grey 3M 5. 12x 7020 Cool white SMD LED’s 6. 0.8mm copper wire ~12cm
Prepare a small work area using some double-sided foam tapes. The grey 3M ones would be ideal as they can withstand heat slightly longer. Press the aluminum cage on the tape to create an outline of the ring. Place a 6mm tube right in the middle and arrange the 12 7020 SMD LEDs around it as shown. I am using 12 of these because… I cannot fit in 15 LEDs to make a smoother 5-step animation.This is the basis of the electronics propeller. The 6mm ‘tube’ at this stage shapes the size of the LEDs. It is also almost the fitting diameter of a styrene tube which I will be using later. The assembled LEDs are small enough not to touch the aluminum cage. The ‘tube’ was actually from an eraser cap in one of my mechanical pencils.Using the 12-LED template, make a small ring with some copper wire but also, leave a length of wire connected to it. Coat it with rosin solder flux and then tin it with solder. This will be the Negative terminal for the LEDs and also, part of the structure to hold the LEDs in place. Yes, my 30W soldering iron is rusting but they usually lasts me for a few years.Next, using a cotton bud or sharp wooden skewers, dip some solder flux and coat the long solder pads (example shown via yellow shading) with rosin flux. Then apply some solder, just enough to coat it. The solder flux helps to coat the LED’s solders quickly so that the heat won’t affect the double-sided tape’s glue. Another way is to apply the solder to the soldering iron tip and then touch the tip to the solder pad where the solder will magically flow into them.Position the copper ring in the middle of the LEDs and solder them to the pre-tinned soldering pads of the LED as shown. You can do this by tapping the hot soldering iron bit between the solder pads and the copper wire ring. The solder will melt briefly and fuse the two together. This process should not take more than 2 seconds for each LED. Anything more than that risks damaging the LED.
Although it is not important but if you really want the ring to be flat against the LEDs, do not melt the solder to the LED’s solder pads first. Here is how you do it: 1. Lay the tinned copper ring flat on top of the LED 2. Melt some solder on the soldering iron tip 3. Use a metallic tool/object to press the copper ring against the LED 4. Tap the soldering iron tip on the LED’s solder pad 5. Repeat this with the opposite LED and so on until all 12 LEDs have been soldered.This is how the electronic propeller looks like when I remove it from the double-sided tape. I am doing this just to show you but you CANNOT remove the propeller until the next part.
TESTING THE 7020 SMD LEDS
You need to test the 7020 SMD LEDs again at this stage. This is to ensure that the copper ring has been correctly soldered to all twelve LEDs. Using the analog Multi-meter, set the dial to the bottom right of the DCA quadrant, x10 (15mA).
Take the Positive (Red) probe and connect it to the copper ring (Negative). The using the Negative (Black) probe, touch on each of the Positive pad of the SMD LED. If the LED does not light up, it is either damaged from soldering, bad solder joint or, the LED is bad. There is also another possibility that the meter’s metal probe could be oxidized and needs to be cleaned.
We are using the Resistance Test from the Analog meter, set to give about 15mA current. Do not worry if the Positive (Red) probe goes to the Negative of the LED and vice versa. This is how the analog meter worked.
Hopefully the LEDs are fine and if not, do not panic. Melt some solder to the suspected LED and test it again. And if it still does not light up, just remove the LEDs from the double-sided tape, melt the solder to free that faulty LED, put in a fresh 7020 LED on the double-sided tape, lightly coat its solder pad (and not put a blob of solder) with solder, then re-position the electronic propeller next to the new LED and solder it.
Next would be the soldering of the Positive wire to the LEDs. Each wire will connect to three LEDs in a parallel fashion and it’s a little complicated.
THE INTAKE: CREATING THE ELECTRONIC LED PROPELLER
In this section, I will show you how to solder the 4 signal wires to the 12 LEDs. Don’t worry. You can do this. It’s easier than looking for PE parts that ricochet off the able and onto the carpeted floor…
I have enlarged this wiring diagram to show you how to solder to the four signal wires to the Positive solder pads. Each of the 4 wires (as intentionally coloured differently but as long as you label yours, it’s OK) are connected in parallel to a set of three SMD LEDs who are about 120° apart from each other. Each wire represents one frame of animation; and I only need to make the ‘propeller’ move four frames for a full 360° rotation. So, you only need 4 frames of animation from the 12 LEDs to complete the illusion. In the end, the electronic fan seems to be spinning without any hiccups. In summary, there are only four wires to the LED Fan blade and not 13.
Just like before, you will need to coat the smaller positive solder pads with rosin flux and then apply solder to the pads. Also, it is a good idea to label each signal wire too. If you want, you can use different colours for each wire but make sure the GROUND is black for easier identification. The wires I am using are quite thin and I do not have any name for them. They are about 0.6mm~0.7mm or so, with 7x 31AWG wires inside. At first glance, they do look like those wire-wrapping wires but once you unsheath them, instead of a single wire, there would be seven.Let’s start with one propeller or the first frame. This is how I did the soldering for one set of fan blade (out of four). Take a length of wire about 10 to 12 inches, then work backwards from there. Take one end, strip about 5mm, tin and solder the wire to the last LED’s solder pad. Measure and then strip/scrape the plastic off the wire (do not cut!), tin and solder to the second LED’s solder pad. Repeat this step for the first LED. Then label your wire. Repeat this for the other three sets of LEDs, we’re creating four sets of three parallel LEDs.Test the electronic propeller again. This is similar to testing the 7020 SMD LEDs individually as shown earlier but this time, we are testing the Positive signal wires. You can set the meter to DCA Quadrant at x10 (15mA), connect the Positive Probe (Red) to the copper Ring and touch all A, B, C and D cables with the Negative Probe (Black). Each signal wire will light up a set of THREE 7020 LEDs. Do not worry if the LEDs are dim, as you just only need to see if they light up at all.
If all the LEDS lights up, as in three LEDs per wire, your Fan Blade is done. Carefully peel it off the double-sided tape. If you yank it too much, either the copper ring will bend or, the solder pad of the LED gets torn off. In the later stage, I will explain why these LEDs were soldered like so.Measure the 6mm styrene tube from the end of the aluminum cage to the front and cut to length, leaving about an extra 1cm or so. Make sure the tube is aligned well in the middle so that the electronic propeller’s contacts would not touch the aluminum cage (OK, you can place a thin tape at the edges of the aluminum cage just to be sure). After gluing the tube to the front, use hot-melt glue to position the electronic blade to the tube. Once done, twist all five wires together. And make sure the labels does not come off.This is how the LED Fan blade position would be.Again, I used Mr. Color #116 RLM66 Black Gray for the aluminum cage and the plastic holder after I primed it with Mr. Surfacer 1000 (Because I do not have Mr. Metal Primer at this stage). Although it scratches easily, I am still quite happy since I need the cage to be well, ‘abused’. This is a shot of the electronic fan being tested. In the end, I moved the LED fan closer to the aluminum cage. With such small holes and obstructions, you’d think there was an actual fan in there, being backlit from inside…The Aves Apoxy was used to mount and align the aluminum cage to the lower fuselage. Note that I did not spray the aluminum cage all the way nor did I spray its insides. I suppose I could but the paint would absorb the LED’s lights, destroying the spinning effect.
Congratulations on getting this far! In the next chapter, I am going to show you how I built the electronic propeller’s controlling circuit. It would be slightly technical and challenging but I hope you can understand all of it. The article deals mainly on the modifying the specific circuit board for this project. But for the more experienced, they can take it a step further.
