R29, R30 And getting rid of isolated dc dc converter.

[aycarambaa]

Hi, I like your soldering station design. Unfortunately, I am unable to find any information on R29 and R30, what formula should I use to calculate it?

My next idea is to simplify the scheme a bit by getting rid of the isolated converter and simply adding a wrapped transformer winding. Do you think it will work fine?

[foldvarid93]

Hi. The idea behind the DC-DC converter was simple. I had to use a single secunder wired transformer for the whole design. If you can solve this problem with a double winded transformer instead of the DC-DC converter, you can do it. The supply of the MCU need to be separated from the power part. I used optocouplers and isolated supplies, but you can reimagine it if you have better idea. Please if you can rationalize the project share your idea with us. :) And the R29 and R30 need to be selected for your HW individually. You need to tune the treshold values for the zero crossing detector as precise as possible. I used a variable resistor and measured the output of the comparator. When I found the settings which is narrow enough and robust enough at the same time I changed the variabe resistor to fix one(s). This is why I designed the feedback voltage divider like I did. If you get an exotic value you can use 2 different resistor to get the perfect matching with the divider's theoretically best value. If it is not needed you can make a solder bridge from one of the series resistors' pads. :)