@Paul: the 0-crossing detector isn't a problem, but the firmware currently is
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(I have sketches for measuring the mains frequency (that will be done only once at startup) and phase control, but I have to add reading the POT for speed setting and the hall sensor for RPM calculation, too.)
As far as I can tell right now the hall sensor is triggered by 2 magnets which are mounted on the (what's the right word?) cooling fan on the back side of the motor.
I can not tell for sure right now, but I guess this means 32000 interrupts per minute (or around 533 Hz), which shouldn't be a problem for the µC I guess.
Currently I'm not yet sure about the crystal frequency I have to use. Either internal 8MHz oscillator or a crystal with 16 MHz or 20 MHz ... whichever is better for the timers ...
after a 0-crossing I have to wait a moment, too, right? I somewhere read that it shouldn't be triggered immediately.
Well, I started with a fancy layout and then was told to reduce costs, lol
so now I have a smaller circuit, it's nearly done "on the paper". The new circuit is meant to replace an old one that uses a triac controlled by U211B.
This IC (and I guess every other phase angle motor controller IC) isn't available anymore. Neither the TDA2021 (or 2023?), nor the TDA1085 etc, it's all done with µC now ...
So to be able to write the firmware using the arduino IDE I selected the mega328 and made a tiny PSU using a 78M05 after a VIPer12, I'll have around 200mA@12V, enough room for the peripherals.
For 0-crossing detection AND mains frequency measurement I use a H11AA1 and to trigger the triac I use a MOC3023.
I hope both will work flawless on either 115V or 230V, I'll have to test that later, I use 2 47 kOhm 500mW resistors in series. At 265V (worst case) it's around 700mW power dissipation, if I didn't calculate it wrong.
I might be done with schematics tomorrow and I'll post them later for discussion
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that's the current status of my project
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)