009: MOUNTING THE ELECTRONICS - Piscean Works

Slowly, it is coming all together. Putting the electronics into the model sometimes can be very challenging. There are a few issues I can think of:
1. Wiring being squeezed or cut when the model is closed
2. Exposed connections being shorted
3. PCB (Circuit Board) getting loose inside the model and causing potential shorting
4. Aluminum tapes use for light blocking in contact with the circuit
5. Too short a wire

MOUNTING THE 0805 SMD LED TO THE INSTRUMENT CLUSTER

Coming back to the flashing red 0805 LED, I just need to make sure it is placed just behind the red button which has been given a clear red paint earlier. The button can be too bright and so, you might want to mount it slightly above or below the opening of the red button and use the reflection onto the button instead.

Here is what I meant. If I put the 0805 LED directly under the red button, it would be too bright. So, I moved the 0805 LED slightly upwards and use the clear resin’s internal reflection instead. Luckily, I did not use silver as basecoat for light blocking because in this situation, the silver would amplify the reflection of the LED’s light and defeats the idea. But if you are using the opaque plastic part, there are a few choices, namely:
1. Slowly and carefully drill a 2mm hole, just slightly before the actual square block, or,
2. Cut off the square block and drill a 2mm hole in its place, then re-create the block with a clear part, or,
3. Remove and replace the block with a 2mm LED, etc.

I don’t have the picture of how I mounted the 0805 LED at the back of the instrument cluster. I just used a black (yes, black!) hot-melt glue. This is more or less the shot I took after mounting the 0805 LED to the Instrument Console. The twisted red/blue wires have not been tucked away yet.

LED FAN BLADE SPEED

The speed of the propeller needs to be adjusted. If you make the circuit go too fast, the illusion of the spinning propeller might look a little unconvincing. If you did it too slow, you will notice that the red button on the instrument cluster does blink. So, we need to find that balance, ie the Lazy Speed.

See the R4 variable resistor at the almost top right? It has a code ‘503’ (for 50K value) printed on its white knob. In the middle is a rectangular slot which you can stick a screwdriver into it to turn the knob. Or you can use your fingers. (OK, so I soldered another set of this electronic kit, again, using my own set of wide-angle warm-white LEDs as I got bored and because I had more than one board.)

Start by turning the knob (yellowed circle) clockwise until you reached the end. At this point, the propeller is spinning very fast and the red button is lighted up. Now, slowly turn the knob in the opposite direction until you see the red button blinks at a very nice rate, where the ‘o’ is pointing to about 2 o’clock. The propeller is also spinning lazily too. That is the speed I am aiming for, the Lazy Speed. The flashing red button is noticeable and also, the ‘propeller’ is spinning slowly and is almost believable too.

MOUNTING THE CIRCUIT BOARD

Although the Falke is hollow, I am going to put the PCB at the twin booms instead of at the rear of the cockpit. There is a small trench in the middle which allows some parts of the PCB to slit in. The rear of the Falke is already heavy so doing this would really make the model off-balance. But luckily, I am using that strong CCTV stand. In the earlier test-fit, how the PCB is slotted depends on the position of the big VR4 variable resistor. In the end, I like the wire arrangement of the PCB as the power cables points to the rear for the Falke whilst the wiring for the electronic propeller is still manageable.

Underneath the one of the booms, there is a small little trench which I use it as an anchor point and then filled it with hot-melt glue. This way, the PCB is mechanically stable. The whole idea is to mount all the electronics inside the model with only one pair of wires coming out, ie. the power cable.

Well, we’re gotten this far and there is a little more before I can call the electronics done. The following segment will continue with the Falke’s twin boom’s spotlights before show you the whole circuit.

TWIN BOOM SPOTLIGHTS

This is the final part of the lighting modifications that I have been doing on the Falke. In the earlier article (006: The Falke Engine), I have mentioned that you need to drill out a hole for the 3mm LED. I am not sure if a slightly smaller 1/8” bit will do as it is easier to friction fit this LED to the plastic part than to set it in place with epoxy or hot-melts.

Here is the image again. The other side of this plastic part (the rear side) is sunk in and this is where you decide on the location for the 3mm LED. A 5mm LED would be a tight fit though and it’s not recommended.

Again, do leave the pair of cables long (about 12 inch) and twisted. These will be connected straight to the USB’s 5 volts of power. As an afterthought, if you like, you can look for those special 1.8mm LEDs too and mount it besides the 3mm LEDs but it will be cramped. Blue might make it look cool and you can do this by getting a pure white version and then coat it with clear blue paint. Because the LED is actually white, your current limiting resistor would still be 68 Ohms.

I am using a pair of high brightness 3mm warm-white LEDs and not the pure whites as I have decided earlier on to give the Falke an old-school light bulb technology look. So, it’s a simple matter of soldering some 68 Ohm resistors, get some 12 inch wires, slip in some heat shrinks and you’re done.

And with this, I suppose, concludes all the electronics for the Falke. In the next segment of the Falke’s electronics, I will show you the whole connection circuit.

One last look before we start closing the model…

THE CONNECTION DIAGRAM

This is the final segment of the Falke’s Electronics where every discussed section is shown and how it is connected all together. The concept is very simple:

Use the power from the USB (5 volts) Power Bank as power source
All non-sequencing LEDs will be connected directly to the 5 volts, each with a current-limiting resistor
Only the electronic propeller circuit and red button LED goes to an off-the-shelf PCB from a DIY Kit

And there you have it. Easy, right?

WHY NOT PWM?

I suppose I could save the power drain of the LEDs further by creating a PWM circuit. The technique is to trick our eye’s Persistence of Vision (POV) by making the LED blink so fast that we see it as constantly ‘ON’. In PWM, during the time when the LED is not switched on, minimal power is used and so, there is a significant power saving. However, this would complicate the Falke’s electronics and I want this to have simple, cost effective lighting and with off-the-shelf solutions if possible. Moreover, if I were to take photos or videos of the LEDs in PWM mode, it will definitely cause havoc with the digital cameras due to its fast flickering. Furthermore, some eyes are very sensitive and they can actually see this effect.

THE ARTICLE BY ARTICLE BUILDS

Anyway, the next page of this article lays out all the work required when lighting up the Falke. It might look daunting at first but as long as you keep your wires twisted and labeled you’re good to go. By following these articles, I’ll bet you’d never would have believed that you have come this far!

The Falke Connection Diagram

Take a deep breath. It’s not that difficult if you do them in small steps.

One of the last few shots before I start on the next chapter which is to close the model up. Notice that I have cut off a small corner off the blue PCB so that the two halves will fit.