Hi,
Andreas,
Some comments about the EMC problem with a PWM controller.
I have tested extensively with a aluminium tube oven with resistance wire wound around it.
I then connected the resistance wire to one of my function generators.
Dit a frequency sweep and measured the field inside the oven, HORROR!
Next step, winding the resistence wire Bifilair on the tube, this was a big improvement.
But even with low frequencies there were big spikes.
This is the oven with the bifilair and also double windings fore parallel (power on quick heating and serial for normal use)
The yellow wire bundle are the three sensors, one for the ovencontroler and the other for measurement and savety (high temp)
![](http://www.bramcam.nl/Arduino/Testoven/TestOven-14.png)
So the next step was to remove the scharp edges when using a square wave.
Below is a part of the schematic I use to limit the EMC of a P.ID controler build around a Arduino or Teensy micro contoler.
The 10uF capacitor remove the sharpedges, the P.I.D. frequency is about 1Hz a 3Hz.
![](http://www.bramcam.nl/Arduino/Testoven/TestOven-03.png)
And yes.. making this oven is difficult
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif.pagespeed.ce._hfWAz_QHO.gif)
The wires are not allowed to touch each other.
![](http://www.bramcam.nl/Arduino/Testoven/TestOven-13.png)
Testing the EMC in the oven.
![](http://www.bramcam.nl/Arduino/Testoven/Inductie-02.png)
Testing with a square wave.
![](http://www.bramcam.nl/Arduino/Testoven/Oven-Bifilair-sturing-03-Blok.png)
And this is how it looks after removing the fast edges.
![](http://www.bramcam.nl/Arduino/Testoven/Oven-Bifilair-sturing-03-Blok-0.2mSec-Edge.png)
For more info look at this link and use google translate...
https://www.circuitsonline.net/forum/view/133966Kind regards,
Bram