I thought it was about time I documented some of this, so here we are.
Many thanks to HB Steve and to DaveC (from the other forum) for their invaluable help.
~A
== Overview ==
There are three main electrical boards; main controller + firmware chip, heater relay board, display board. The controller board has a different transformer based on the voltage (I believe there are two variants supplied 110v, and 230v). The firmware also has Celsius and Fahrenheit variants.
The Gene works by blowing very hot air through an enclosed drum. The controller board simply determines when to turn the drum motor, when to power the fan, and when to apply heat.
There are two temperature sensors on the Gene, mounted inside the metal conduits at each end of the drum. They both appear to be identical parts and are driven by identical electronics. The heating element end sensor monitors the heat from the heater and instructs the controller to kill heating power when the preset temperature is met.
The drum exit sensor is used to determine the indicated display temperature.
The controller board uses a relay to switch mains voltage to the heating element. The relay engages to disconnect power. This means the element is either full on or off and can't be partially on.
The fan is can be driven at two speeds, normal and fast (for cool down). The firmware simply adjusts the reference voltage supplied a voltage regular to vary the fan speed.
A similar approach is taken to change the motor speed (in later revisions). The controller reads the drum end position sensor to ensure the drum always stops in the same position.
The electronics are powered from a voltage regulator feed from a small onboard transformer.
The firmware raises an error if the inputs significantly differ from what is expected. For example, it will report if the heater temp is not changing (dead element) or has risen too much (fire).
The firmware is a common 40pin PIC microcontroller, with a fair number of unused pins.
== Firmware ==
The dates shown are firmware revision/build dates. Obviously, the back panel dates will be later.
The main control board is virtually identical between revisions, however, there are enough changes that a firmware revision will only work correctly in a board of the same vintage. For example, a rev 5 chip will not work correctly in a rev 0 controller board.
Firmware Rev 0 (unmarked - Nov 05)
If the unit comes from a 230v batch (see back panel), the element may rapdily switch on and off from around 200 degrees. This may make is impossible to reach 2nd crack within reasonable period of time.
Firmware Rev 3 (June 06)
Element switching is very significantly reduced and may be non-existent.
Drum rotates at half speed when on its final revolution before stopping.
Motor drive circuitry improved.
Firmware Rev 5 (Dec 06)
Drum now marked 'Max Dry Processed' rather than the cryptic 'Max Brazil'
Motor gear assembly modified.
Internal cable routing improved (this may have occurred in v3 also).