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yottabit

Golden Member
Jun 5, 2008
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Not sure if it fits here but I always recommend Dan Gelbart’s “building prototypes” playlist to new mechanical engineers - he covers things like sheet metal fabrication, precision machining, and tricks for building prototypes. He’s got so much experience I can listen to him talk all day. A world apart from the “makers” on YouTube

Edit: Oh and you might like his video on historical scientific instruments:
 
May 11, 2008
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Not sure if it fits here but I always recommend Dan Gelbart’s “building prototypes” playlist to new mechanical engineers - he covers things like sheet metal fabrication, precision machining, and tricks for building prototypes. He’s got so much experience I can listen to him talk all day. A world apart from the “makers” on YouTube

Edit: Oh and you might like his video on historical scientific instruments:
I think it is great. Generally speaking : People who find this thread interesting should be able to select what is relevant for them at a given event in time, independently.
 
May 11, 2008
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Sciencedaily. All about science.

 
May 11, 2008
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This is a very informative youtube video about currents flowing and the return path.
And it shows what happens to the (return )current flowing in the ground plane when the groundplane is continous and when the ground plane is actually split up or has an interruption in the groundplane.
And how the resulting return current flows.

Pictures taken from TI (Texas Instruments), app note :
Picture A, DC to low frequency, current and return path.

Picture B, high frequency to very high frequency, current and return path.

Picture C & D. Groundplane with interruption.
For signals, you can use stitching capacitors or layer switching + stitching vias.
The use of stitching capacitors might also work for large currents but i do not know if anybody ever tried it and if it has any benefits EMC wise.

phl2.jpg
phl1.jpg

If you want to be a good pcb designer, this is required knowledge.

It is applicable to high speed signal design, like for example USB or PCI-express.
And very much applicable to smps design. SMPS stands for switched mode power supply. Just use search terms like "hot loops" in combination with smps.
Think Jim WIlliams, Bob Pease, Linear Technology(now Analog).

SMPS switch at very high speeds. And therefore, the return path is just as important as the supplying path. So the big NO-NO is to break up the Ground plane under a SMPS circuit when it comes to supplying current and also with the output current. Thus, never break up the ground return path or the supply path.
Always keep hotloops in mind. And keep the supply capacitors that provide the transient currents close to the package or the ringing and therefore the EMC disturbance will get out of hand and uncontrollable.




General youtube site from Ken Wyatt :


As a hint and a great tutorial about smps design , but also usable for class- D amplifier design, inverter design, motor driver design :
 
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A good experiment where the positive result can be very useful for those youngsters and eager old geezers with a small wallet to determine if a home made product is not radiating EMC interference like crazy.
Also handy if you are working on a product in the professional work environment and you are not too sure about your work and want to have some sort of relieve before going for the precompliance testing or compliance testing.
Anyway, a good experiment is to test if this way of measuring the currentflow can be done with the tiny SA spectrum analyzer together with a proper probe and a digital signal generator or cheap (homemade) comb generator. Which is very cheap, only 65 euro.



Tiny SA website :

There is mention of a comb-generator being used.
Cheap signal generator from JOY-IT :

Near field magnetic probe :

The specific probe used :

Official emc website for accreditations and emc compliance in Europe and the USA :