First circuit board design project - part 2

Part Two

After quite some time to get used to eagle and understand it a little better I've managed to revise the schematic from part one and also get started on the board layout.

Instead of laying out the pins in long rows like in the first schematic I've decided to instead put the pins in groups of three. You can see that on a nano breakout board the pins are arranged in groups as well. It's also much easier to find parts for in Eagle, which does in fact make a huge difference. I also realized that the board footprint for male pin headers is exactly the same as that for female headers. That one had me stumped for a while. I'm now also using an arduino pro mini template. This means I now have exact measurements for the dimensions of the pro mini, this will be very useful when it comes to laying out the board. I also changed all the LEDs resistors and caps to be the 0805 size. This is a common size used in board design and will be easy to find components for, unfortunately surface mount soldering is difficult at the best of times and this will make the components smaller and even harder to deal with. I also added an extra two A6 and A7 female headers, these are connected together in series. I added them because depending on which pro mini you are using, the analogue pins A7 and A6 may be in different locations. In the board layout below you can see the two different locations commonly used by the pins.

I made a start at laying out the board, I'm still learning and this draft has errors. I found it really interesting but also frustrating. Its so great this board project is actually coming together and if I can keep this momentum up I plan to actually have it manufactured and it will be for sale on tindie.com . If you haven't heard of tindie its a website where independent hardware developers can sell products. Check it out.

Anyway, that's all for this update. I've got more Eagle tutorials to watch! Thanks and until next time.

First circuit board design project - part 1

Part One 

As an arduino enthusiast a particular arduino pro mini has caught my attention recently. For those that don't know what the pro mini is, it's a very small and typically low cost arduino. It is an attractive board to me since I like projects to be compact and yet still functional. However during the prototyping stages of a project using the pro mini can be very fiddly so I would like to create a pro mini expansion board. The board would not be unlike the expansion boards available for arduino nano. (see below)

As you can see the board isn't particularly complex so this will make a nice first design project for me. However I do plan on making this my own a little, for example the arduino pro mini does not have a USB to UART converter chip on board, I suppose you could blame this on the small form factor of the board. Instead, every time the user wishes to flash new code onto the board they must use a USB to UART converter board. Such can be seen below.

The chip used on this particular conversion board is the CP2102 by a company called Silicon Labs. There are also other chips which do this conversion function such as the FTDI FT232RL, which is built into my arduino nano or ATMELs very own ATmega16U2 which is used on the original arduino boards. Another example is the CH340G which is occasionally used in Chinese "knock off" arduino boards this also does the same conversion job no hastle.


The board pictured above is manufactured by Haoyu electronics, after some rooting around online I was able to acquire a schematic for that particular board. This was useful since many of these CP2102 converters are similar I now have a much better idea of how I need to lay out the UART section of my board.

Additionally the board should be able to receive power from the USB port, and of course perform the "breakout" function. Below is a rough draft schematic I have come up with so far. Please bear in mind this is my first endeavor with both circuit design and eagle so it is a little messy and I'm still skeptical as to whether or not it will work but it's a start never the less

Thanks for reading, this will be a multi-part project and I shall keep updating as I continue to revise my design and learn more about hardware design. Thanks and until next time.