Our lab is completing an experiment looking at long-term effects of obesity on motivation to work for food.  The question is, "are obese mice more or less willing to work for food than lean mice?"  One way this can be tested is with a "progressive ratio" schedule, in which the first pellet requires one poke, the second two pokes, the third four pokes, etc.  We can ask when the cost will be too high to continue.  You can read more about this here.  

To test this in our experiment we needed 20 FEDs.  So we decided to build them!  It was the largest FED build we've attempted and it went super well.  Building 20 is different from building 1, and we learned some things that I'll adopt in the design to make manufacturing easier.  But we got 20 FEDs built in ~2 days.  Photos from the build below: