Microcontroller PCB for Attitude System (Thesis)

Didn't feel like coding yesterday, so I decided to make a uC PCB for the attitude sensor stack. I wanted to make the PCB a little more general purpose than just a PCB for interfacing with the sensors, so I've added pin-rows for all I/O-pins with annotation. Other than that, I've added header for USART, two I2C headers, a voltage regulator, and three regulated power headers. As with the other sensor PCBs, I have added 3.5mm mounting holes in the corners so that the cards can be stacked.



I'm trying out yet another PCB fabricator, iTeadStudio, which is by far the cheapest I've seen. For ten 50x50mm two-layered, green solder mask and HASL plated, it cost $14 including shipping! I also added the 'Open PCB' option, which is where they will send you two random PCBs from another order. How cool is that!

I am a little concerned that I've pushed the tolerances a bit, but we'll see when I get the PCBs. ITead specify 6mil a minimum, and recommend 8mil (0.2032 mm), but I think it should be fine.

I'll probably get the boards in a couple of weeks time, until then I will keep program using Atmels STK600 monster of a dev kit. I'll get a ICD debugging header so I don't have to lug it around with me, not to mention that horrible ZIF socket system...

First use of Multi-Purpose PCB (UV timer) - Part 1

This was to be a timer system for UV exposures of DIY PCBs. I have already made up and used the UV board, but it was a bit messy to use (pull the power to turn off).

The idea was to have a button for start/stop, and a rotary encoder for adjusting exposure time. Sadly, the encoder was DOA, so I will order a new one. In the mean time I've coded the display, and found out that the atmega8 doesn't have a PC7 (forgot about that), I had wired it to ground on the PCB. This meant I had to some pair wire instead of the 10-pin header.

The FET works brilliantly, and you can see the UV board hooked up, but not on at the moment. When on, the FET doesn't even get hot to the touch, so no need for a cooling rib.

So before I get a new rotary encoder, all that is left to do is to wire up a start/stop button (reset button is already in place).

New PCB service

Made up a sort of prototype PCB in CADStar and sent it away to a new manufacturer I'm trying out. I'm pleased with the quality, two layer eletrical, solderstop, two sided silk screen, and very cheap. Just two minor errors on the PCB on my part: I used 6mm switches instead of 3mm, and there's possibly one air wire, but that could be an auto-router glitch. In the image below, I've mounted the microcontroller, ISP, and a header for unregulated power. This was to test the microcontroller, which worked like a charm.



The board is based around an ATMEGA8, and has most of the standard parts is use: regulator, a few switches, a FET, rotary encoder, USART, I2C, and ISP of course. In addition, all IO ports are fully connected to 2x5 STK500/STK600 type headers with power: Any additional circuitry I can take from the pin headers.

Gerbers, schematics and PCB-file available on request.

Happy hacking!

Combined Accelerometer & Gyroscope

This is from my Master thesis, where I'm building and attitude refference system (ARS) for pitch/roll/heave and vibration compensation for echo location systems.

I've buildt two kinds of accelerometer sensor boards already, based on Freescale and ST-microelectronics chips. The latest addition is the gyroscope board, based on a chip from Invensense. And here they are, finally merged (with the Freescale accelerometer board).



I'll be using Labview and Matlab to implement my ARS algorithm now.

Later I will build a power and interface board, and of course the micro-controller board, making the final system a four stack fully modular design.

Happy Hacking!

Repurposed thin-client as a simple server

A while back, I aquired a Termtek TK-3350 thin-client for next to nothing. The computer came with a version of windows CE on a CF-card, which was mounted on a IDE-adapter card.

I wanted to see I could make a low-cost, low-power and silent server for simple stuff like game-serving and voice-chat.

Swapping the 64mb RAM with a roomy 512mb module, I did experiment with putting Linux onto a bigger 1gb CF-card I had, but eventually gave up. I did succesfully install a few light-weight distros onto it, but none that I liked. The ones I like wouldn't run, probably because of the odd hardware (a VIA C3-533MHz CPU and VIA chipset).

I needed more storrage, so I installed a 30 gb 2.5" HDD, drawing power direclty from a 5V rail I found. The yellow tape is Capton tape, heat-resistant and so on.





I installed MS Windows 2000 this last time, It worked out quite allright. I've ran it for several hours, and it gets no warmer than 48C. Since then, I've drilled two wholes in the chassy, and permanently mounted the HDD.

At maximum load it draws 25W, which i mainly the HDD. If I'd kept the CF rather than installing an HDD, it would probably have drawn less than 10W.

Chinese mini USB power adapter blows up

I haven't looked into why this little adapter blew up, but clearly QC is not a priority. Notice the protruding sot from where the explosion deflected of the USB plug. Probably not a good idea to leave these plugged in when you're not in the same room...

HTC Hero Docking station mod

Been a while since I've written anything, so I tought I'd do a short write-up of a mod I did today.

I was not happy with the ugly and bright blue LED (sooo 2009) on a HTC Hero docking station I picked up on ebay, I set out to dim that azure light-house, replacing it with a mellow crimson.

As this will sit on my night-stand, this was given top priority.


Popping the cover revealed a much simpler device than I expected, nothing more than a few wires, a mini-USB, a LED, and a resistor.







Prying away the LED, I simply snipped the LED and resistor off, leaving enough stub to solder on the replacement LED and resistor.







The original resistor was a 460 Ohm (1/8 W), but since blue LEDs in general require a higher voltage than red LEDs, I opted for a 1180 Ohm (1/4 W).






The only other thing I did was to add some shrink sleeving/wrapping. In this picture I was testing the mod before gluing the LED in place.






And there you have it, a nice and warm red glow that won't disburb me in the night.




I hope you've enjoyed reading about this simple mod just as much as I did doing it. Good night ;)