Space Battleship Yamato (Bandai 1/500)

[The Inner Geek]

I wonder if you can port a speaker that small? Porting is usually just for bass though as far as I know. Maybe line the inner hull with accoustic foam? A quick google search for "Solid looking speaker grill"  comes back with nothing useful, otherwise I'd say find a material that looks solid, but isn't.

[Will Vale]

I wondered about micro-drilling metal like the Apple LEDs which appear to glow through the aluminium, but it would mean getting a friend to CNC-machine flat metal and then forming it to the shape of the hull - probably too complicated. I think the best bet is probably to cut out as much as I can get away with and install some PE mesh or styrene louvres. Then I can paint it to make it look like it's supposed to be like that. At least it's at the bottom of the hull, if the third bridge could be omitted it'd be a lot easier!

The foam is definitely a good idea, I've been playing about with polyester wadding but I think something spongier would be better - it does help though.

[edited for spelling and missing words, dearie me...]

[Grail]

NIce. Love the fast and furious bass 

Can't wait to see how this turns out after seeing all your previous stuff.

[Will Vale]

Well I haven't exactly done more on this yet, but I have done quite a bit of research into power options. I originally thought I might have the batteries and electronics in a box in/under the stand, but since I've managed to get the speaker into the ship it'd be nice to have the rest of it in there as well. It just feels more "right", plus I think it'll be cool to run around the room with it making noise and flashing :)

I need a supply at 5V (for the servos) and 3.3V (for the audio module). The amp and microcontroller can run at either voltage, so I'm tempted to add a 3V3 regulator to the microcontroller board and run al the logic at the same level. That seems easier, so then I only need a supply at 5V. I don't know much about electronics so the following is based on a bit of reading around - contrary to what I was saying before about modern electronics being easy, the power supplies are more difficult since you're dealing with analogue circuits not digital logic circuits.

You can get 4.8V with 4 rechargeable AA batteries, but that's quite a big battery pack. You can also step down from 9V using an inefficient linear regulator or a more efficient low-drop-out (LDO) regulator but the energy density of 9V batteries is a bit rubbish. I thought I was going to use something like the MintyBoost but apparently the kind of buck converter that project uses needs quite careful PCB design (to separate the high frequency paths from the high current paths) and I was hoping to build it on stripboard.

Then I saw this in the Sony catalogue:

Space Battleship Yamato (Bandai 1/500)

Click for bigger

It's a 5V USB portable mobile phone charger. Which means it charges from USB at 5V, and provides 5V to charge other USB devices. Plus it cost 30NZD (on special) which is around what it would cost to buy the components to build it, except it's pre-assembled, tested and in my hands right now :) It also has two big advantages over other things I looked at: it has a 2Ah capacity, which will run Yamato for hours, and it can supply at 1A continuous, which is more than enough for starting up when all the servos will want to draw current at the same time. Apparently the Hextronik micro servos are quite power hungry and can peak at 750mA, although it's unlikely I'll see that since they'll be lightly loaded.

The only problem is it's a bit big, but I think I can stuff it in the rear of the ship and have the micro-USB socket accessible at the back (by removing the engine cone) for charging. I'm not sure if I can make the rear turret move, but there might be room to get a drive in there somehow. I guess I'll find out.

Space Battleship Yamato (Bandai 1/500)

Next step is to modify the rear hull and make some mountings for the board. I bought some Tamiya 3MM U section styrene which ought to make nice clips for the PC board edges. I also need to test and see if I can draw power directly from the USB socket mounting points on the PCB or whether it does some kind of output detection before it turns the output on.

Modelling with electronics is definitely slower than modelling without - I spend a lot of time reading and thinking rather than doing. It'd help if I had more knowledge, but I suppose I'm learning a bit as I go...

Will

[Will Vale]

This is still not a very modelling-heavy thread, but I built all the circuit boards for the audio side of things, power, and the microcontroller at the weekend. Then debugged them and changed a whole lot of stuff - it now works pretty well!

This is the USB charger from the previous post, modified to a) provide 5V without using the socket (since there's no room for a plug) and b) switch the the power on and off by shorting the ground pin to the little spring on the socket. This normally completes a circuit when a plug is inserted into the socket (because the socket chassis is grounded) but I've replaced this with a toggle switch. Simples!

Space Battleship Yamato (Bandai 1/500)

Click for big (plus notes calling out different bits)

This is the audio board, which is the SOMO-14D module mounted on a bit of stripboard, with an LM2950 regulator and capacitor providing a stable 3.3V power supply from 5V, plus pins and bits of wire to make all the power, control and output audio connections:

Space Battleship Yamato (Bandai 1/500)

Here's the microprocessor - this is a mostly-Arduino-compatible board (Teensy++ 2.0) which is really really small, and cheap, and more powerful than the standard Arduino Uno. Nice. I've mounted it on headers and cut two stripboard "wings" which fit inside the hull and provide a bit of space for connections and any bits of support circuitry:

Space Battleship Yamato (Bandai 1/500)

The ribbon cable is for the audio, and the double row of headers is a 5V power bus to plug the other boards into (and eventually the servos as well) - the two headers are isolated from the stripboard and ganged together on the back with wire.

Space Battleship Yamato (Bandai 1/500)

The cheapest, simplest and smallest bit is the amp itself - this is a breakout board from Sparkfun for a Texas Instruments amp intended for phones and PDAs. I tried wiring directly to the board but the joints were fragile, so I added headers and soldered the leads to those instead, with heat-shrink to insulate the joints and make them harder to bend/break.

Space Battleship Yamato (Bandai 1/500)

It does all fit in the back, but I won't be able to rotate the rear turret. Never mind! If I were able to design and build my own surface mount PCBs (much harder than what I'm doing) all the chips could probably sit on one tiny board.

Space Battleship Yamato (Bandai 1/500)

Space Battleship Yamato (Bandai 1/500)

Actual Modelling Bonus (tm) As a break from all this soldering I stuck together and primed a little 1/350 U-boat over a couple of lunchtimes last week. Good practice for working with PE parts:

Space Battleship Yamato (Bandai 1/500)

I think I should start building the Yamato LED assemblies and figuring out if/how they'll fit soon.

Cheers,

Will

[NickM]

I think it is really great to see a model wip that is very unusual and different. Even if it's not very modelling heavy, I like to check this thread because I have really high expectations for where all this is going! 

[Hunter Rose]

Wow thats some serious skills Will, I wouldn't know where to start with that lot!!

[Sharkdog]

Yeah, I'm with Hunter, I wouldn't know how to get something like that set up. Very impressive!

[Will Vale]

Thanks folks, but please don't be put off trying this stuff - I was pretty much an electronics virgin at the start of this. I've done plenty of wiring for my railways, but that's just variations on connecting point A to point B. There's loads of electronics and microcontroller info on the 'net and if you can read and follow instructions it's not that difficult to get started.

It helps if you aren't disheartened by cock-ups (and can recover from them) but that's something all modellers have to deal with :)

Apart from various broken joints, lack of continuity, and things not working, the biggest mistake I made with this so far was hooking up the sound module power supply the wrong way around. I noticed that the regulator was very hot and unplugged it just in time. Luckily no magic smoke was created...

W

[The Inner Geek]

I don't know anything about anything. But, the engineers where I work sometimes need custom boards and use a site/service called Pad2Pad. I have no idea how much it costs to have them make you a board, but I know they do low runs... like one.

The electronics are coming along nicely! I won't lie... I'm a little dissappointed the rear turret won't turn. It seems a little silly to have awesome turning turrets in the front then have to lean in and manually turn the rear turret. How much room isn't there under the rear turret? Could you rig up a pully and connect it to the closest front turret? Just brainstorming.

[Will Vale]

That looks like a good service, and it would be cool to have those professional-looking boards!

Bad news about the rear turret - not much room at all. I thought about a pushrod running over the speaker from the 2nd servo under the front deck, but I'm not sure there's even room for a servo horn at the back. I also need to leave space to get to the reset button through a hole under the turret. I'll see what it's like when I get the wires folded neatly but don't hold your breath...

[Sharkdog]

Well, I got my hands on a 1/60 Dom, which has a bit more electronics inside than I originally thought. So I'll be trying my hand at fitting that together sometime too :)