I've found out the the thermocouple in my W.E.P. 858D+ model does not seem to have ground connection, which is good.
I started a new Project (Eagle 7) at
https://github.com/0xPIT/Air858/tree/master/hardwareThe PCB fits into the sub-40€ W.E.P 858D+ stations available from eb*y. The hardware seems comparatively OK, even has proper earth connection in the hand piece. PCB uses this odd-ball s*msung controller.
The intention is to simplify the schematic, using a MAX31855 to read the thermocouple, use single-MOSFET PWM for the fan, and a 126x64 OLED display, plus a rotary encoder alongside the two buttons. Some parts of the original hardware can be reused.
The idea is to use wave packet control in software, as I did for my
https://github.com/0xPIT/reflowOvenController. So I need detection of zero-crossing. I think I'll eliminate the 2nd optocoupler (a dual antipolar led type) and detect the zero-crossing by tapping the signal from D5 and adding a 2nd diode to arrive at the desired 2x mains frequency.
Any suggestions? Feedback is welcome.
- pit