Hardware design issue

Author	Message
Mixtel90 Guru Joined: 05/10/2019 Location: United Kingdom Posts: 8964	Posted: 11:04am 05 Dec 2024       You have to watch external supplies. You shouldn't connect the output of a SMPS to mains earth unless it's designed for it, for example. There is a class Y (I don't think it's X in this case) capacitor between mains earth and output negative to reduce RF emissions. Earthing the output shorts it out and the output starts to radiate RF. A low voltage AC supply can be centre tap earth and the two (fused) ends of the winding as a twisted pair to reduce radiated hum. If the earth tap is on the centre of a WW pot that's connected across the winding rather than the transformer you can tune the radiated hum down to almost nothing! . Edited 2024-12-05 21:06 by Mixtel90