Moebius Cylon Raider 002

[04032012 0435]

First Design

This is the first attempt at the PCB design. I used a PCB software to create the design, then cut the pattern and glued it to a cardboard which has the approximate thickness of the actual PCB. If you look at the photo above, the PCB is very short. I have to adjust the length of the pillar until it is correct. This is because I cannot leave the area after the pillar (Left) too long as it will affect the ability of the board to tilt about until the LEDs are visible through the visor. Also, I have to make sure that the other end of the PCB (Right) has just the right spacing and fits the shape of the 'head'. Note its very unusual shape and in order to do this, it is not easy (in other words, it costs more).

Also, the design of this circuit uses a mircocontroller instead of the more commonly 555 & 4017 IC pairs . Moreover, the specs of this circuit is beyond the old skool chips. The requirements are:

1. A left to right to left LED sweep

This is something the 4017 cannot achieve as the sacrifice for the output puts means that you will get 5 LEDs out instead, not to mention the addidtional components such as more resistors and diodes. There would be a lot of re-wiring both on the circuit board and PCB which again, takes up space or more cost if they were to be deisgned as double-sided PCBs.


2. Semi-flicker Thrusters

Again, the 4017 cannot do this and in order to achieve this effect, adddtional 555 and 4017 chips are required. Furthermore, when this is done, the space taken up by these chips, even when using the SMD equivalent, is still too big and also, it consumes more power.


In conclusion, the microcontroller chip is the only solution as not only could it fulfill the above requirements, it can still do more. All in the size of only one chip and no aditioanl extra external components. Moreover, is saves power too as the chip's operating voltage range is between 3.0volts to 5.5volts.


The LEDs I have chosen is the 0805 SMD, which is easier to solder and also, not too small that it can 'lose' itself. I took some 0805 LED and began test soldering them onto a shaped copper wire, which is to be the GROUND Signal. The reason I did this was when I send the board design to the vendor for prototyping, it would be a single-sided PCB instead of the Double-sided. Unfortunately, this approach did not work so well as the moment I solder the next LED, the solder from previous ones would melt and this made them go out ot alingment or drop off. After some time tackling this challenge, I have to say, this idea is out. The idea was perfect when I was doing the Iron Man Toy Arc Reactor and Repulsor units, thinking that it would work but because the LEDs needs to be vertical, the procedure cannot be applied here.


At the same time, I decided to fine-tune the programming for the microcontroller chip which I have been working on since last year. I stopped development for this last year because there was no physical model of the Cylon Raider for me to have a look and design the PCB. Also, my friend Bruce mentioned that underneath the Cylon Raider's wings, there were two missile bays which are dimly lit with RED lights. And so, I decided to upgrade the roving eye LEDs from 8 to 10, have a pair of semi-flicker white thrusters plus a pair of red LEDs for those who wants to do their own missile bay. At this point, I have decided to try with the smaller 0603 LEDs which based on the size of the board, allows me to put in 10 LEDs. If it were to use the 0805, I think the most I can put in would be seven.


Because I needed the board to be as compact as possible, I decided to order the microcrontroller in SOPP format which is very small. But I worry about the fine 'legs' of the chip and not only that, I need to account for the extra pair of 'legs' on the IC. Maybe I should start to look into ISCP as all these are very new to me. Anyway, from the photo above, this is the first PCB design. The width of the board, to my surprise, is the same as that of a USB. Here, is where I made two mistakes from that discovery: First, the idea of designing some USB 'pins' to fit into a USB socket for ICSP purpose was rejected because it would have made the board longer by about another 1 cm, this would haunt me later in the design stage. Second, I should not have used the SOPP format because, using the hand-soldering method, the risk of shorting the pins and/or misalignment of the chip to their pads are very high.

Yeah, I was not thinking right because when the model was passed to me, I went full steam into the R&D. Coupled with that, there were some personal problems which really stressed me out and also, marred my decision-making process.


Second Design

The second design is more or less the implementation of the prototype circuit into the PCB. Because I did not venture much further into the USB idea, I widened the board a little and also included a little dioe as a basic form of polarity protection, but at the cost of a voltage drop of 0.7 volts, which is quite significant since this will be a low power system. One of the contributing factors to the reject was that there were not enough space to connect the POSITIVE and GROUND signals into the proper USB pinouts. Later on, I realised that when I needed to flip the board and so, this idea could still have worked but it would need to be double-sided and due to the lack of space, the unfortunate fact is that most vendors here could not do plated-through holes at the price I am asking.


This is more or less my second design. Note the change (from the previous photo) that I have changed the SMD LEDs from 8 to 10. I am also using the Network resistors for this design since a normal 0805 version was too big. Placed next to a 10 sen coin, the board is about 3.5cm. Eventually, I widened the board a bit since the USB idea was rejected.


There were some bad news when I got the prototypes back. Yes, the pads fpr the SOPP is very fine. The two boards in the background were rejected ones because it was etched the other way round (they flipped the film). Once again, I would like you to look at the foreground boards, where the rounded areas are. This is the problem where manufacturing is concerned. Because normal boards are rectangle, this is fine with the vendor but with that custom shape, they would need to create a mould to cut it. I purposedly designed this area so that the wires from the back area of the board would pass through here. I realised this after taking a closer look at the model kit as this is also the only available area for the wires to pass through without any drilling of plastic parts.


The vendor was kind enough to etch another pair of boards for me with no charge since the earlier ones were in bad condition. I stare at the board and think of the implications if I went ahead. But things are already going though as planned and as such, I have lost 10 days into this. We are so exitec about this project and want to see it installed into the model, all fully painted.


As with every Project, it is a learning experience for me. Here are the SMD Network resistors that I have ordered. Each chip has four resistors inside it and its very tiny. Soldering it will be a bit difficult since their solder tags are located beneath. But I will tell you how it can be done later.


Disappointment came a few days later when both the SOPP chips and the adaptor arrived. The adaptor is of the wrong type. I stubbornly ordered the right one instead of concentrating on the ICSP which solves a lot of problem and saves time. But I would still need the adaptor when I prototype for other projects.


Another disappointment came another time when the SOPP adaptor arrived. it still could not fit into the SOPP chip. And so, another two weeks gone for nothing and I am really depressed. So, now is the time to reflect and make the final design decision.




















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