How to replace the coin cell for the real-time clock

[Lex]

The real-time clock on FED3 uses a 3V CR1220 coin cell, which is estimated to last about 3-5 years.  So if you start getting strange times displayed on the screen (things like 265/265/265 or hugely incorrect dates like 50 years in the future) and it's been >3 years since you changed the battery it is time to swap it!  Luckily it's cheap and easy to do so.  Here is where the coin cell is on the FED3 circuit board.

If the circuit board is not inside a FED3 housing, simply poke the battery out with a small screwdriver (poke where red arrow is) and replace it with a new 3V CR1220 cell, making sure to note that the positive terminal goes up:

If the FED3 circuit board is already installed in the 3D housing you can replace it without removing the circuit board, it's just a bit awkward (but much faster than removing the board completely).  You'll first need to loosen the screw near the Adalogger, which mounts the board to the housing.

Then pull the board away from the housing a bit so you can access the coin cell and poke it out with a small screwdriver. 

Either way, once you replace the battery you'll have to reflash the "SetClock" example code to get the time right, and then reflash your code. Then you'll be good for another 3-5 years!