version 1 - use single TRIAC

Use one TRIAC to trigger firing of TRIAC after zero cross has been
detected.  By delaying the time between zero cross detection and TRIAC
firing, the speed of the fan can be controlled.   This works, but there
is a humming sound when the speed is reduced.   Also, user input is
taken via a IR receiver:
* speed can be adjusted from 0 - 9
* Mode can be
-- auto - where fan is switched off if temperature goes below a
predetermined level
-- manual - where fan is not switched off based on temperature