Arduino pro mini undershield
January 19, 2014
The cheapest Arduino clone on Ebay is probably the small Arduino pro mini clone. I've bought some pro minis on Ebay for less then 3$ a piece from a Chinese seller. It's a tiny board with an ATmega328 running @ 5V. It does not have an USB/serial chip, so you need your own USB to serial converter.
The boards I bought came without header pins soldered on them. But included were strips of male header pins. I do not find these boards very usuable in a project, robot... They are good to prototype on a breadboard but that's about it. I'm not a fan of breadboards. I prefer to connect the different electronic modules I use with wires with female dupont connectors. As this is easy, flexible and makes for a good connection.
So I thought about designing an "undershield" for these pro minis and started playing in Eagle. This is what I have come up with: The PCB has 4 rows of headers. First row is GND, second is 5V, third row is the connection to the pro mini. The fourth row is the female header in which the pro mini plugs in. For connecting a battery there is a small screw terminal. The pro mini is fed through the "raw" pin, it gets the battery voltage through a schottky diode. The male 5V headers pins are powered from a simple linear voltage regulator. I would use a LM2940-5, but a 7805 would also work if you feed it +7V.
What do you guys think about it? I haven't ordered any boards yet but I might sent of the design to China to have 10 made.