Hi.

As a few of you may know, for quite a while (ie more than 8 years) I've been working on a variety of remote piloted vehicle systems, mostly for my own amusement. The ultimate goal is for flying radio controlled aircraft, but quite a lot of the development has been on ground-based stuff for the simple reason that a system crash doesn't involve quite as many bits to dig out of the ground

The latest remote piloted buggy, based on an old electric wheelchair, was at the 10th empeg birthday party that various BBS members went to. The VR helmet system I was using there is about the 4th generation I've designed, and finally does pretty much everything I want but was rather bulky. I redesigned it into a much smaller form factor, and have just finished building the first set of PCBs. The processor board came up perfectly on the first attempt, and I've so pleased (and relieved) I felt I had to mention it

I packed it down from a backpack about 50cm x 60cm x 15cm to a box 10 x 12 x 5cm, and less than half a kilo from around 8kg. The ultimate goal is to build the entire thing into a VR helmet, but that's for later.

There's quite a bit in the box:

CPU board specs

200MHz EP9307 ARM9 processor (not the best implementation around, in fact it's pretty buggy, but I've been working with it for three years and know where most of the bugs are. In fact I found several of them, and how to work around them. The main thing is that it has a very configurable video subsection, which I needed)

64MB PC100 SDRAM
16MB flash
VGA output port
18 bit TFT output
Touch screen interface
I2S codec interface x 3
3 axis +-2/8g accelerometer
3 x serial, 2 at RS232 levels, one at 3V TTL
3 x USB2 HS host ports
3 x USB1.1 FS host ports
SPI
MicroSD card socket
I2C at 3.3V and 5V
10/100M ethernet
Runs from 8V to 24V power with on board SMPSU
Full data and control busses on expansion ports
Loads of GPIO lines

Graphics Overlay Board specs

2 x CVBS/Svideo/Component video input stream capture ports
24 bit TFT output port
VGA output port
24 bit stereo codec (line in, line out, Mic in, S/PDIF output)
Digital video expansion for stacked CVBS output board
Video processor which does:

PIP
PBP
Genlock
Chroma Key
Alpha blending, translucency, etc
Input and output scaling
and many other effects

The idea is that the processor board, which runs linux, generates onscreen graphics for virtual flight instruments from real time telemetry received from the remote vehicle, which the graphics board then blends and overlays onto the live video from the same source, in full colour. The prototypes, which I've been working on for around three years, worked very well, so I finally did a finished version.

Two graphics boards can be stacked on a processor board for full stereo operation. With one overlay board and one cpu card, the whole thing fits neatly into an off-the-shelf aluminium box giving a really nice looking system.

I mention it here as (A) I'm really pleases it works after nearly a year of design work, and three days solid of assembling the PCBs, and (B) possibly someone can think of other uses for it.

pca

Absolutely amazing. Hope to see it in action some day.

FTFM.

Absolutely.
Awesome.

Nice work, I wish I could design PCB's of that complexity. Out of interest, did you have to put 'everything' on the boards? Do you do the BGA stuff yourself with a reflow oven?

I got the BGAs mounted by a company that does vapour phase reflow. £10 per chip, by far the cheapest I found anywhere. I am, as it happens, slowly building a reflow oven, but this project was too important to try experimental soldering techniques on.

I stuck down everything else. The 0402 resistors, etc, are easy enough, but the 0804 resistor networks are a bit of a pain.

pca

The soldering looks really neat, I imagine a good deal of solder paste, flux and patience was used!

There's pretty much everything you'd possibly want on those boards. What's the per-board cost assuming they were pre-assembled?

Wow! Just too cool for words !woW

So you designed it, sourced and obtained the parts, and soldered them all onto the board. Here I was proud of myself because a couple weeks ago I managed to solder together and shrink wrap two wires replacing the battery in my Karma without burning myself or setting the house on fire.

Sigh...

tanstaafl.

Don't use solder paste actually, I've always found it to be more trouble than it's worth. I just use fine flux cored solder. When building for my own purposes, PROPER solder as well, not that lead free crap

It's fairly easy once you've got a steady hand, a good soldering iron, and twenty years experience Lots of flux is essential though. I go through a lot of flux pens.

As far as the costs go, it's going to depend on quantity. One off, the component cost is in the hundred and fifty pound region, but that's subject to massive revision downwards once the quantities go up. The PCB is the least of it really - the boards cost about £18 each 10 off from a chinese manufacturer which is pretty good for a good quality 8 layer board 120mmx100mm in small quantities. The price drops like a stone when the quantities go up as well.

There's a lot more to the cost than the actual cost as well of course, but I'm certainly planning on selling the things if possible. I have a customer for them already, for embedding into a completely unrelated and non-obvious (and fairly expensive) project, and hopefully this will get the quantities up to the point where the cost is reasonable.

So far I've managed to test everything except the ethernet, which is going to take some effort. First, I need to persuade the horrible cirrus linux distribution to actually compile...

pca

Amazing! That is beautiful.

I've always wanted to build something similar, using GPS for navigation and GSM (cell/mobile network) for communication. Then you could fly cross-country from your computer You could also make it fully autonomous.

By the way, do you have any opinion on gumstix?

Can you point me towards your PCB manufacturer please?

Edit: Forgot to say - nice work!

Yeah, me too! Just post it here, even.. more than one or two of us could benefit!

Cheers

Impressive! I too am curious who you had do the PCBs and BGAs. Love the blue solder mask by the way.

Stu

The PCBs are made by a company called FASTPCB, in China. Pretty sure it's these people, the logo they put on my boards is the same I used a company called ALR Services, who then arrange the boards to be made whereever. They're one of the companies I've used for years, and I've always had good service from them. There is a NRE charge for making the boards which is rather variable depending on options required, but the cost per board was about a third the price of any other quote I got. This was on 10 day turnround.

The BGA mounting was done by Allgood Technology using vapour-phase reflow which doesn't need a stencil, the expensive bit in prototyping. It was £10 + VAT per device mounted. Turnround time was about 5 days.

The blue is very nice, yes. The funny thing is that the two PCBs are noticeably different colours, although they were made by the same company at the same time!

pca

We just had our first production run of boards for a new project done out in china because the price was just sooo good.

We did however have a fit when our pick and place contractor decided that they wanted to charge us nearly £20 more per board for mounting components than we expected, suffice to say, we told them to get stuffed!

We are now seriously looking into a small pick and place machine because it'd be easy to amortize the cost of it (and oven) over a longer period - plus it opens up the ability to mount BGA's in house which would be a massive benefit in development.

Nice looking work patrick!

Even more cool toys??

I like the place you work! And I've never even seen it!

Cheers

If you do that, I may have some business to put your way

Well, I now have all the USB ports running, the VGA output and LCD outputs working, all three serial ports active, and the I2C going. The next step is programming up the video digitizer and the framestore processor, a total of about 620 registers to set with the correct values. What fun.

Can't get the ethernet working at the moment, not sure why. I suspect a minor hardware fault somewhere. It's not too important right now as a usb to ethernet adapter works fine.

pca

Linux, presumably?

Yes, 2.6.25 kernel with modifications. I may need some help with drivers, any takers?

pca

Geek update:

We bought the machine, have used it quite a lot and it's now being traded in...

Our new machine which should be here in a month or so will place components down to 01005. it's also much faster than the old outgoing machine.

So you guys must be doing small volume production runs, not just tiny batches (?)

Volumes are on the increase. In fact, as soon as we build what we think is a reasonable batch, they've been ordered and are then out of the door!

The problem we have, is that running smallish batches with a sub-contractor tends to cost an inordinate amount of money and there's good reason for this.

Changeover.

We make quite a few different products and because we designed them all they tend to have a big overlap between components, but even then some of the boards have a massive difference outside the core components, you can easily lose half a day simply changing components from one build to another.

If you're a subcontractor, then this means your machine is out of action and you're having to pay staff to reload the machine, if you're only running a small batch then the overheads are huge, hence high cost for doing the pick and place.

Our new P&P machine has an amazing feeder system which literally takes seconds per feeder to switch components, so even for us it represents a massive time saver. We also don't have to do kit prep, boxing, shipping etc - it's all in-house. We've got our eye on a jet stencil printer as well, would then be able to use the pick and place for prototype work!

Plus it's mesmerising to watch the machine in action!

Got video?

kind of on topic, but right in my line of work:

http://www.wired.co.uk/news/archive/2011...=Outbrain+Trial

The new machine arrived last week and the engineers spent the week commissioning it.

Spent monday and tuesday loading our old layouts onto it and then reprogramming the components. (given the technology step between the old machine and the new one we figured that it was worth going through the extra step to make sure the performance is as it should be).

I'll take a video next monday which is when we're actually going to use it to make some boards.

I have to say, the linear motors on it are awfully impressive. The whole machine uses linear motors (even the magazines) everything is very quick and precise.

It'll probably be the most boring video in the world, but hey ho....

Well, here's the machine in action, not the worlds most exciting video....I guess you kind of have to be staring at the machine to get mesmerised!



The red flash you see is the line scan camera, this camera can take up to 50,000 pictures a second and performs the optical centring of the components on the fly, this is a massive upgrade on the camera system that was on our old machine.

That particular camera is located on the left hand side of the y-wagon (the part that holds and moves the PCB in and out), hence the reason for the 8mm feeders being on the left hand side of the machine as it can optically centre them on the fly.

The machine itself uses linear motors for the X & Y movement as well as on the magazines for feeding components, it's pretty impressive technology.

Most components on the product we were building can be placed with the hydra head, this picks up 8 components at once (up to so8 sized components). The single mount head picks up anything larger than that.

The feeders on the machine are what are really impressive, probably the best system on the market, quick & easy to load.

We're very pleased with the machine, it's a massive upgrade on our old machine!

Adrian

Cool. Something I've always wondered about, is what keeps the dry components in place after the machine puts them there? Some kind of adhesive, I reckon, but how does that happen?

Thanks!

Just the solder paste, it's tacky enough to hold components in their place, the only time we see problems is with components with high mass, such as big surface mount inductors.

You get round that problem by setting the "group" (think mount priority) higher than normal components, that way the machine knows to place those at the end. You then tell it that the acceleration on the X & Y needs to be slower than normal.

You have to change the group as well, because once a component has been placed that has lower accelerations, those become the maximum accelerations that it'll use, and if the machine decides to plonk that component down first, then everything after it will be slow.

It's a neat system, the machine itself self optimises as it goes to try to increase throughput.

You can use glue, but that tends to be for double sided reflow on high mass components - so that they don't fall off in the oven. It's also messy and not want you really want in your expensive pick and place machine. All that happens is that there's a special nozzle on the machine that dispenses a blob of glue where needed before it does the pick and place.

Adrian

Nifty. When/how does the solder paste get applied?

It's the first stage, we have a stencil printer which applies the paste to the board. The shim is made of steel and is etched by laser to expose where the paste needs to be applied.

You just the panel into the stencil printer and then it uses a metal squeegee to apply the paste to the panel.

However, the people who make our pick and place machine have a jet printer which can apply the paste, think of it as a big bubble jet printer that dispenses paste instead of ink.

Video below that I took of it in operation at their UK office!



Again, this machine uses linear motors and it moves incredibly quickly. The forces involved are so high, that the actual black "casting" you can see inside is a granite that has been ground to a powder and then formed into a shape with a resin, it weighs several tonnes!

Obviously screen printing is always going to be quicker, but the advantage of this machine is that you don't require stencils to be made (they're about £100-£200 each) and it can vary the amount of paste to be dispensed on a pad by pad basis - you can also avoid putting paste down where you don't need it (in the case of build variants etc) which you can't do with a shim.

Oh, it also costs a cool £100,000!