Cheers for the help! I'm a little sorry about not lighting any kits before. I never realised how straightforward doing two or three LEDs is, and how easy it is to run things off a wall wart if you want to.
Bandai big 1/2 BB-8 build
- Thread starter Automaton
- Start date
Cheers for the help! I'm a little sorry about not lighting any kits before. I never realised how straightforward doing two or three LEDs is, and how easy it is to run things off a wall wart if you want to.
Very inspiring build. Thank you for all the pictures and all the step-by-step informations.
Only problem is... You made me want to buy this kit now !
It's loads of fun. An expensive project though! I can't do much more until the weekend, but I can continue to plan the electronics, which is requiring me to learn lots of new things.
The MP3 player circuitry will run through a 5v buck converter which has reverse polarity protection (hooray!) but I shall take special care nonetheless not to wire things backwards
Also, I'll avoid drawing too much current from the generic 12v DC 2A supply I have so I don't overheat it. The buck converter supports a 3A max output, 2.1mA optimal max. I take it the buck converter draws only a small amount of current itself to do its job? The MP3 player board is designed to work off a 3.7v battery or a USB, so I'm presuming it uses less than an amp, but the buck would cause the current to increase in that part of the circuit (which will be a parallel and self-contained module to everything else), would it not, so I would imagine I don't need to worry too much? I have about 15 LEDs, which I imagine will run to 300-400mA total?
I'm trying to understand this DC-DC magic. Okay, not magic — conservation of energy. Would the maths for maximum the buck could output be (PSU volts x (PSU amps - LED draw)) to get maximum wattage through that part of the circuit, then divide that by the buck output voltage? So (12v x 1.6A)/5v = 3.84A if the buck was 100% efficient, which is more than its designed for.
Am I getting close? :/
pave spectre
New Member
I will start with the caveat that it has been a little while since I have done muh with buck or boost converters, so hopefully someone with more recent experience will also chime in.
not sure what that "optimal max" rating is, have never encountered that before. If it;s the output at which the converter has maximum efficiency then it sounds rather poor, unless you meant 2.1A?
How much current the converter uses to do it's job will depend on the percentage efficiency, and the actual output it is being run at.
No. If the converter is rated to 3 amps at 5 volts, then the maximum output will be 3 amps. Depending on the quality of the converter you might be able to push it beyond that rating a little bit, or you might be close to breaking point running it close to the maximum. Depends if the rating has a safety factor, or if it has been wildly overstated(not uncommon in my experience). If your converter has adjustable voltage output, and is nominally rated to 3A@5V, then output current can vary depending on what your voltage is set to.
Assuming that you are running the converter at max, 5V 3A, and assuming an efficiency of 90%, your 15W ouptut works out around 16.7W input, which for a 12V supply is around 1.4A input, less than your available maximum supply current.
Your actual values will all differ depending on the rated efficiency of your converter, and your actual load current values.
It also depends on if you have a true buck converter, or if your device is actually a 3-pin regulator. For a 3 pin regulator I might expect to see a sizeable heatsink.
not sure what that "optimal max" rating is, have never encountered that before. If it;s the output at which the converter has maximum efficiency then it sounds rather poor, unless you meant 2.1A?
How much current the converter uses to do it's job will depend on the percentage efficiency, and the actual output it is being run at.
No. If the converter is rated to 3 amps at 5 volts, then the maximum output will be 3 amps. Depending on the quality of the converter you might be able to push it beyond that rating a little bit, or you might be close to breaking point running it close to the maximum. Depends if the rating has a safety factor, or if it has been wildly overstated(not uncommon in my experience). If your converter has adjustable voltage output, and is nominally rated to 3A@5V, then output current can vary depending on what your voltage is set to.
Assuming that you are running the converter at max, 5V 3A, and assuming an efficiency of 90%, your 15W ouptut works out around 16.7W input, which for a 12V supply is around 1.4A input, less than your available maximum supply current.
Your actual values will all differ depending on the rated efficiency of your converter, and your actual load current values.
It also depends on if you have a true buck converter, or if your device is actually a 3-pin regulator. For a 3 pin regulator I might expect to see a sizeable heatsink.
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Thanks. It's sold as a proper buck converter, not a 3 pin regulator. I found a better English description and it runs without a heat sink at 2.1A.
Genius! Thanks! I spent so much time toying with doing some parts in series that I overlooked that option. I even found a 5w iPhone charger plug just the other day! Now, just need to think about what plug I want at the BB-8 end of things...
pave spectre
New Member
That makes more sense. To run at at the full 3 amp you would need to add a heat sink, but from the sounds of your setup you don't need quite that much anyway.
If your led currents + mp3 player board current are more than 1A total, 5W won't be quite enough.
Yep. I still haven't been able to find any specs on the MP3 board that give the draw, so I'll get my multimeter out to double check that. Worst case I suppose is I need a 10w USB charger.
Looks like I have a couple of options though.
Orbital Drydock
Active Member
I think you guys mean Volts "V/E", not Watts "W/P", 5v is logic level power. All arduino & most breakout boards run on 5v. Some have a voltage regulator & 12v tap to handle V above 5V. When it comes to current draw Amps "A/I". What's most important is what is the total current draw of the entire power system lights, sound, etc. & that the power supply will provide enough current. You can also math out the total current draw if you know the draw of each component or branch of the system. Ohm's law really comes in handy. If folks aren't familiar with it, the formula is PEIR P-watts, E-volts, I-amps, R-ohms. If you have any 2 variables, the rest can be figured out by writing PEIR vertically & multiply up, or divide down.
P- 10.5w
E - 5v
I - 2.1a
R - 2.38r
Cheers! That's really useful. Sorry, I've used so many Apple products I identify all the chargers by wattage as that's how they categorise them. 2A/5v.
What should I figure for a passive speaker (I forgot about the speaker
)? Just use the maths above? The MP3 board recommends a speaker rated at 3w, 4ohm, but the amp only supplies 2w, so would that be divide 2P by 4R then get the square root, which would be just over 0.7 amps at full amp volume???Orbital Drydock
Active Member
Cheers! That's really useful. Sorry, I've used so many Apple products I identify all the chargers by wattage as that's how they categorise them. 2A/5v.
What should I figure for a passive speaker (I forgot about the speaker
That's the correct formula. Though it only gives you the speakers current draw in the board, not the entire component draw under power. Load up a long loud mp3 & current test the whole component at full volume. Loving the build!!
Thanks everyone! This thread has been a real education. I do tend to learn things by starting fairly big and working backwards, I'm afraid, so thanks for entertaining me while I work it all out.
Back to the buck converter and the 12v 2A PSU I have as an option.... Going on Pave Spectre's description and some research I've done, I think I have the maths now.
Let's say I run the sound circuit through the buck converter and let's presume the 5v MP3 player and speaker are pretty hungry and use a full 2A between them. That draws 10w of power just to do the work.
So the input *into* the buck converter would be 10w at 12v, which equates to 0.83A current draw PLUS a few milliamps extra as it isn't 100% efficient. Let's say it's only around 80% efficient. So input into the buck converter in that case is 12v at just over 1A?
On a 12v 2A PSU, if that were all true, it would leave nearly 1A for the rest of the electronics? And it would mean I'll be fine with the bits and bobs like cables and connectors that are rated at about 2A?
Back to the buck converter and the 12v 2A PSU I have as an option.... Going on Pave Spectre's description and some research I've done, I think I have the maths now.
Let's say I run the sound circuit through the buck converter and let's presume the 5v MP3 player and speaker are pretty hungry and use a full 2A between them. That draws 10w of power just to do the work.
So the input *into* the buck converter would be 10w at 12v, which equates to 0.83A current draw PLUS a few milliamps extra as it isn't 100% efficient. Let's say it's only around 80% efficient. So input into the buck converter in that case is 12v at just over 1A?
On a 12v 2A PSU, if that were all true, it would leave nearly 1A for the rest of the electronics? And it would mean I'll be fine with the bits and bobs like cables and connectors that are rated at about 2A?
pave spectre
New Member
Without sitting down and doing the complete maths, what you describe sounds about right.
Lights!
The top on has one blue LED, one flashing red. The middle just has a white. The bottom one flickers randomly. You can see that light doing that when they're on Han's freighter. There's one more I can do without drilling a for the hole for the wire... on those, I'll need to solder the socket after I've painted and assembled it. All running as separate modules off a DC splitter cable (well, the bottom one is taped to a 9v battery in this pic!).
The top on has one blue LED, one flashing red. The middle just has a white. The bottom one flickers randomly. You can see that light doing that when they're on Han's freighter. There's one more I can do without drilling a for the hole for the wire... on those, I'll need to solder the socket after I've painted and assembled it. All running as separate modules off a DC splitter cable (well, the bottom one is taped to a 9v battery in this pic!).
Big update!
I've had an LED production line on the go. For some reason, I keep breaking the white ones... the legs seem to come off. I have, by the way, gone with 12v because I realised I bought a lot of stuff for 12v so as I think I know how the buck converter works now, I'm going with plan A.
It's also been decent weather so I got to paint! Here's my set-up: a £5ish Ikea Lazy Susan and some cardboard. Works great. The orange went on well.
Here you can see that the range of tones the orange gets in different lights isn't far off the prop. You can also see the hole for the electronics. I didn't drill these... I used a screw-tipped awl to make small holes then reamed them out with a tapered reamer until.
Which all amounts to... the first fully complete panel, electronics and everything. One note: when these go together, they're going to be tough to take apart. If you're worried about maintenance, cut the plastic out behind the LEDs.
And of course it means no test fitting.
I've had an LED production line on the go. For some reason, I keep breaking the white ones... the legs seem to come off. I have, by the way, gone with 12v because I realised I bought a lot of stuff for 12v so as I think I know how the buck converter works now, I'm going with plan A.
It's also been decent weather so I got to paint! Here's my set-up: a £5ish Ikea Lazy Susan and some cardboard. Works great. The orange went on well.
Here you can see that the range of tones the orange gets in different lights isn't far off the prop. You can also see the hole for the electronics. I didn't drill these... I used a screw-tipped awl to make small holes then reamed them out with a tapered reamer until.
Which all amounts to... the first fully complete panel, electronics and everything. One note: when these go together, they're going to be tough to take apart. If you're worried about maintenance, cut the plastic out behind the LEDs.
And of course it means no test fitting
.
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Very cool work so far.
I was just a Target and saw this, about the same size and $50.00 (Star Wars Deluxe BB-8 Action Figure 18")
http://www.target.com/p/star-wars-deluxe-bb-8-action-figure-18/-/A-50570800
I was just a Target and saw this, about the same size and $50.00 (Star Wars Deluxe BB-8 Action Figure 18")
http://www.target.com/p/star-wars-deluxe-bb-8-action-figure-18/-/A-50570800
Got lots done today. From a painting perspective, this is a very easy, if big, build. If I hadn't decided to do the electronics, this would likely be finished by now. First I finished the rest of the panels. Here are five of six. The fit could be better on the white parts going into the discs, but I suspect they go together easier without paint. With hindsight, I recommend masking the pegs and peg holes. However, there is al least one where a thinnish section doesn't peg in to anything so flares out a bit.
When I had all six, it was a good juncture to check all the wires reached and fit. Which they did! To recap, there's an 8-way DC splitter cable in there. Apologies for not getting any pictures of the wiring harnesses, but they're pretty standard. You can also see the hole I drilled that will come out through the base. Or that might be the head, depending which way up I decided to have the body, in which case I'll run the cable the other way up.
The next job was to properly paint the head and get priming the white panels. I painted the lower portion of the head. The main dome needs some proper light-blocking work as well as the seam filling above his eye and another seam round the back. I reckon I'm going to turn this hexagonal box into a base and put a sand texture on the top.
And here's as far as I've got today. The white panels are primed and I've done the panel lines in Tamiya neutral grey. The deep detail lines that Bandai were bragging about are pretty much only reached by paint if you do a wash. That's good and bad... if you're use to priming, doing the lines and then letting the top coat knock the lines back, it doesn't quite work like that. So they're a little strong on the orange but they grey should stop them looking too cartoony on the white. I hope.
And no bad light leaks! the long blank piece on the lower right is a bad fit, so I let it bleed through there because blocking was a pain and I'm pretty sure that lights up sometimes anyway.
No leaks here.
It's starting to look the part...
When I had all six, it was a good juncture to check all the wires reached and fit. Which they did! To recap, there's an 8-way DC splitter cable in there. Apologies for not getting any pictures of the wiring harnesses, but they're pretty standard. You can also see the hole I drilled that will come out through the base. Or that might be the head, depending which way up I decided to have the body, in which case I'll run the cable the other way up.
The next job was to properly paint the head and get priming the white panels. I painted the lower portion of the head. The main dome needs some proper light-blocking work as well as the seam filling above his eye and another seam round the back. I reckon I'm going to turn this hexagonal box into a base and put a sand texture on the top.
And here's as far as I've got today. The white panels are primed and I've done the panel lines in Tamiya neutral grey. The deep detail lines that Bandai were bragging about are pretty much only reached by paint if you do a wash. That's good and bad... if you're use to priming, doing the lines and then letting the top coat knock the lines back, it doesn't quite work like that. So they're a little strong on the orange but they grey should stop them looking too cartoony on the white. I hope.
And no bad light leaks! the long blank piece on the lower right is a bad fit, so I let it bleed through there because blocking was a pain and I'm pretty sure that lights up sometimes anyway.
No leaks here.
It's starting to look the part...
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