Some Googling found me this:
Patent EP1510768A1 - Dehumidifier with a defrost control system - Google Patents
It's a patent file for a dehumidifier demand defrost. I think I could implement this with the Fischertechnik parts. It would solve my issue of the set temperature value system I believe my current Dehu Defrost has. I think it just senses coil is below 32*F, waits a set amount of time, and defrosts for a minimum set time and until the sensor is above 32*F. The obvious flaw being I can't run my HTHP in <32*F which is a good portion of the winter, when I want it most.
Adam