Tag Archives: PCB

Sometime it just works…

Those are rare moments but sometime it happens:
My brother-in-law gave me a very simple schematic drawing (a ppt file ūüôĄ ) asking if i could “turn that into reality”. It should be a Arduino shield to measure vibrations created¬†by passing trains (in German that’s a “Zug Ersch√ľtterungs Detektor”).

Well, out went trusty Eagle CAD and some interpretation fun began. Some components were described as “resistor 1-10k” others had unknown dimensions like “pushbutton bought at eBay”.
After sending some photographs¬†back and forth I was pretty clear that everything makes sense… and after some optimizing ¬†the shield had plenty of space left. So in went a nice breadboard section with the option of placing a RTC there as well.

Then the DirtyPCB drill started again – and after 2.5 weeks the PCBs arrived and bro’-in-law happily started to assemble the “ZED 1.0”.
What should I say? It just worked. Immediately… ¬†wow. That should happen more often, or like Hannibal says “I love it when a plan comes together”¬† ūüėČ


IMSB012 C004 replacement

The IMSB012 is my favorite TRAM carrier board. Room for max. 16 (size-1) TRAMs and plenty of external connectors. The perfect¬†platform to build a successor of the ‘Tower of Power’.

Like with all TRAM carriers having more than 8 slots, it was a good decision to put at least one C004 link-switch onto the board.
While that’s generally a good feature, you (and me) might not need the option to reconfigure your Transputer network several times a week… And if you’re completely sure how you like your network it would be better to set if once and for all without the signal delay penalty you have to pay using one or even two C004s.

So in my case, I’m perfectly fine with the 4×4 matrix mentioned in the B012 manual (and also used as an example in my C004 post). So instead of using the clumsy MMS tool and having an extra link used into the T212, I planned tp remove the T212 and the two C004s and replace them with two dummies. Pretty much the same way like Parsytec did it with their x’plorer.
First I had to chew myself through the B012 schematic to understand the connection of each TRAM slot into the C004s. After that it was time for some intense cable plugging:

C004 dummy test

If you plan to do so, please be aware that the socket holes are too thin for a normal (0.63mm?) jumper cable. You might ruin your socket if you use force to plug them in!
I created a interpose socket by using single row pin header sockets which itself had thin enough pins to fit into the original B012 socket.

After some corrections, the buzzing-through of all 16 slots went fine and the schematics went to the PCB house (I have some PCBs left, ask for a quote if you need some).

And this is how the C004 replacement PCBs look when completed:

IMSB012 C004 dummies

Again, to solder in the pins, you’ll need really thin ones. Thinner than 0.5mm that is. Also, you don’t need to populate all 84 pins, I only use 51 per dummy¬†(bridging some gaps).

Additionally, I strongly advise to isolate each¬†dummy’s top with some kind of tape to avoid (electrical) contact to the TRAM placed above it. This is how they look seated on the B012 underneath slot 6 and 14 – the T212 under slot 7 not yet removed:


Manufacturing PCBs in China?

Ever thought about manufacturing PCBs in China?

If you google this, you most certainly end up with “your mileage my vary”. Indeed it does… and here are my 2 cents:

Because the grass might be greener on the other side of the river, I’ve tested and will keep on testing several PCB houses over the time. So I’ll update this Blog post every now and then… until now, I wrote about


For my AM-B404 TRAM I hadn’t had any other option than have them manufactured in china. 6 Layers and sub-20$ weren’t possible anywhere else. So I tried ShenZhen2U
After sending in the Eagle-CAD files their support was great. Manufacturing and shipping was OKish (20 days in total). At first sight, everything looked great. Nice, professionally framed SMD stencil, PCBs carefully bubble wrapped.
When holding the whole stack of PCB it felt a bit ‘bouncy’ – looking at it from the side, it became clear why:


Some PCBs were bent. You can see the gaps between some of them.

Well, when the PCBs were separated (I had 3 panels in ¬†PCB) it wasn’t that obvious anymore. So I started populating them.
This brought me to the next issue. The silkscreen was quite a bit off on some of the PCBs. Luckily, all of them had enough solder pad left to be usable:


In the end, 3 of the 60 boards were completely unusable. They had shorts within the internal layers which couldn’t be fixed even by cutting traces and re-wireing.
I guess all those glitches are the price you have to pay when going “cheapo”.

Update: I ran a 2nd batch of the same boards from the same gerber files and mentioned the non-working boards in the 1st order.
This time the quality was very good and they silently added 2 extra boards to my order. Thumbs up, ShenZen2U!

Dirt Cheap PCBs

For my QFP-to-BGA adapter Рwhich just uses 2 layers РI tried Dirt Cheap PCBs. I really like the attitude of their site and for just 25 bucks for 10 PCBs it was worth a shot.
It’s a no-brainer. Upload your eagleCAD/Gerber file and wait – after some minutes you can even look at a rendering of the top- and bottom layer of your boards. They explicitly state, that this function is beta and yes, 1 of the ~5 times I used their service, that rendering wasn’t totally correct – so don’t wet your pants if this happens. Use a real gerber viewer instead. That said, you normally have 1-2 days to update your files if I might have found a mistake later.
About 20 days later I got my little brown envelope. Everything’s fine, I’m totally OK with it.
Before using their service, be sure to check their FAQ. You’ll find jewels like this:
The board house will add three tiny numbers to your board: batch ID, a customer number, and our PCB ID. This is so everyone knows which crappy PCBs to send you. Don’t like it? Tough. Buy an entire panel somewhere else.

Update: I also tried their 4 layer service (for which they use an external board house) and while the price is good, the results were OK’ish.
They did not place the solder-mask on the most fine-pitch part (QFP 100pin) which is a pain in the a** to reflow without getting shorts ūüôĀ


A more posh version of manufacturing PCBs in China is¬†Seeedstudio¬†who asked me to check out their “Fusion” service. They even offered me a $30 coupon (thanks!), so why not give it a try?!

Before sending my gerber files I had a couple of questions and their email service is very good an responsive.
As they offer hard-gold finishing, I thought it might be a good time to create an expansion card with its connectors being plated with hard-gold to make it more robust to plugging the card in and out a couple of 100 times… some mails flew back and forth but in the end they asked for the same price for having the connector-fingers done in hard-gold as having done the whole PCB done in this process (the rest was planned in HASL). That’s 30 vs 230 bucks! Erm, no thanks… not this time.


So I ordered some standard 2-layer, HASL finished PCBs, no bells and whistles on Fri. Nov. 25th. Their order form is well designed and shouldn’t leave you with any questions – they even offer a gerber viewer of your uploaded files, which I think is very cool!
(One hint: When entering your address, the form insists that you enter an EORI tax-number which private persons normally don’t have. A simple dash “-” does the trick, though).
They offer 3 ways of shipping, ~10‚ā¨ for normal post (10+ days), DHL and FedEx (both 3+ days). I went for DHL – I’m pretty sure “normal post” wasn’t an option for my order when I had the choice. Maybe because of the weight…
Next day the boards went into production. ¬†You’ll be updated about the proceedings by mail – pretty standard today – as well as in you accounts order history on their page.

On Nov. 29th I got an email confirmation, that my PCBs are finished and shipped… and on Dec. 3rd I got the boards in my mailbox. That was blazing fast indeed! 9 days from ordering to receiving


The cool thing is, that I’ve ordered the predecessor of this design at “Dirt Cheap PCB”, so I have a direct comparison.
Given the simplicity of the design, I haven’t found any glitches or mistakes… the two boards are nearly identical.
If you’re super picky about your design: like Dirt Cheap PCB, Seeed does print some internal ID on your silkscreen – and that’s not in their FAQ.


For a simple design (2-4 layers, no extras) Seeedstudio is comparable to other PCB houses – even a tiny bit more expensive.
Where they shine is when it comes down to support and all those extra features like¬†penalization, V-grooves etc. which the other houses just can’t offer or leave you in the cold when it comes down to getting help.

Do you have/had any good/bad experiences with Chinese PCB manufacturers? I’m happy to hear about it in the comments below!