Couple updates:



An audience member redid my brushless DC motor schematic in the traditional commonplace formatting which for most is easier/quicker to read and understand due to familiarity. So I'm reposting it. It looks mostly accurate although I have since added a 100nF ceramic capacitor between the gate and source of the highside mosfets to reduce ringing issues. Standard practice according to chatgpt. I also changed the LED color to orange because chatgpt said blue would show through the silicone skin more and add a cold inner glow and we want it to look like real skin so no blue.



As to why the highside mosfets get a 100nF ceramic gate capacitor but not the lowside, here was how chatgpt explained it to me:



-High-side MOSFETs:



Their source pin moves up and down with the motor phase (it’s not at a fixed potential).



During switching, the drain and source both move rapidly, and the gate voltage must track that movement precisely — any ringing or inductive noise can momentarily over-stress Vgs.



That’s why we add the small capacitor across gate and source: it tames that high-frequency ringing and helps hold the gate steady relative to its moving source.



- Low-side MOSFETs:



Their source is solidly tied to ground, so the gate always swings relative to a fixed, quiet reference.



They don’t experience the same “floating” gate drive or large dv/dt transitions on the source pin.



So, the gate is inherently more stable, and you don’t need that extra 100 nF G–S capacitor.





Anyways, here is the audience member schematic:







Here is my updated schematic with the changes I mentioned:









In further news, I tediously installed the new 100nF ceramic capacitor between gate and source of the mosfet. Due to the close proximity to the 10k ohm Vgs resistor and various other low temp solder joints in the immediate vicinity, any heat applied would surely have caused those to desolder and the whole thing to start falling apart so I ended up just soldering nickel strips to either side of the 100nF ceramic capacitor (by itself off to the side) and then used the tip of a sewing needle to apply a tiny amount of conductive silver glue onto the gate and source nickel strips coming off the IRLR7843PBF mosfet and then pressed the nickel strips of the ceramic capacitor into that. I put that in front of a mercury vapor bulb for an hour or so to cure and then applied another generous helping of conductive silver glue over the top of the joint. I then baked that another 7 hours under the mercury vapor bulb again. This photo shows the final result.







It appears to be a solid joint and I think this is a great way to make attachments when you can't use soldering! It might even be better than soldering in some cases from a ease of application perspective but not sure yet on that.