I bought the cheapest Arduino Uno R3 compatible board for less than 5 dollars/euros, and this is a small review.
The usb-serial chip is a CH340G, that requires an extra driver to be installed (ch341ser.exe from wch.cn).
- Extra holes next to every pin so wires can be soldered to it.
- Another 8 extra holes to solder wires for power, serial and I2C.
- Pin A6 and A7 are available.
- Normal size 3.3V regulator, more power for the 3.3V.
- Enough vias in the ground plane.
- It is not counterfeit, since they don’t claim it is a real Arduino. It is a yellow colored VISduino.
- The placement of components is accurate.
- Some copper traces are very thin.
- The holes to solder wires could have more copper around it at the bottom side. And they could have more distance to the ground plane.
- The two larger electrolytic capacitors are the same as on other cheap clones. They could be the cheapest ones around.
- The soldering is just good enough. A few solder drops/splats are on the bottom. It seems to be a problem with not enough flux or components that are not clean or a working environment that is not clean enough.
- The USB connector is a micro-USB. I prefer a mini-USB connector.
- It works !
- It might be less durable with mechanical vibrations or low temperatures.
- I would not use it for a project that is running 24 hours a day.
- It is great for testing.
- For cheap boards, the conclusion is often that you get what you paid for. Since the 5 dollars/euros for this board on Ebay is inclusive shipping, I think you get more than what you paid for.