wiki:Prototype/Two

Version 6 (modified by art, 12 years ago) (diff)

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Second Prototype (SMD version)

Prepare

Finally I spend around one month (only my free time) to prepare a layout design with EAGLE for my second prototype. This time it is all based on SMD components and should be pretty small. The problem now is to find a good company which could etch the board for me. I finally stopped at  PCB-Pool.de which did the work really good. I had to order there a 1dm2 board, so that I got second kit for free. For the etching process, I payed around 50.- Euros. For all the components used on the board, I payed again around 80.- Euros. However I had to order the components of the board in big packages. I've received all of them from  RS-Online.de. If I compute the final material price for one such kit, then we will end up in around 60-70.- Euros, just for the material, which is still ok for a prototype.

The final 2nd prototype layout is looking like this:

http://www.tevs.eu/stuff/pcb.png http://www.tevs.eu/stuff/bmw/IMAG0030.small.jpg

Finally after one week the PCBs arrived and I was surprised about the quality. Unfortunately my camera was not available at this time, hence I had to make pictures with my cell-phone :(

Build

After several weekends of soldering (have I told already that I am working only on weekends on this project), I build the prototype into the housing. Now I am using 14MHz crystal to drive the ATmega. Additionally I am using  PCF8574 port expanders to ask for button and rotary encoders state. This helps me also to reduce wirings and to make everything more suitable for this small housing.

http://www.tevs.eu/stuff/bmw/IMAG0032.jpg

Of course, this is a prototype, so not everything went pretty well. I had to patch the board design slightly to meet real-world requirements. This is a close up view (sorry for bad quality) of my hardware patches: http://www.tevs.eu/stuff/bmw/IMAG0033.jpg

http://www.tevs.eu/stuff/bmw/IMAG0034.jpg

VGA input from my laptop for testing purpose: http://www.tevs.eu/stuff/bmw/IMAG0038.jpg


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