Electronics engineer here!
02.02.2025 08:01
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Electronics engineer here!
Very impressive! I’m ranked 14 kyu on OGS. DM me if you want to add each other. I’ve got some learning to do to get to SDK rank.
To my knowledge the best way right now is to bring the layout from KiCad into FreeCAD and then use the OpenEMS plugin in FreeCAD to set up the sim.
There are some awesome videos coming out from this channel: youtu.be/VcJqhsbzR3c?...
Today I tried out OpenEMS. Here's a Gaussian-pulse with a bandwidth of ~5 GHz traveling down a micro-strip transmission line, done in 55 lines of python.
I'm excited to build more complex simulations, like a micro-strip layer transition with nearby vias.
PCB inside an environmental chamber
After over a week of prep, I started running an accelerated life test that I’ve been planning for months.
My Fluke megohmeter and surface probes arrived today, and I grabbed the first static-dissipative tile sample I could find to try them out. A pass for the tile is 10^6-10^9 Ohms.
Sometimes dead-bugging is the best way. 8x 470uF Al-polymer caps on 10 AWG wire.
Here's a board I designed for a client a few months ago! It's basically an industrial controller. It's amazing what some lights, a piece of paper and some patience can do. I know very little about photography, but this looks a lot better than the stills I was taking on my phone.
copper trace on FR-4, surrounded by a cube of air
Step 0 of learning CFD simulation: learn how to create an air volume around my solid bodies (copper trace on FR-4). It's not _hard_, but there just aren't that many tutorials out there.
Thank you for confirming! This is what I suspected, but it’s not clear from marketing material.
@techconnectify.bsky.social a burning question for you: why are heat pumps and ACs rated in “BTU” instead of “BTU/h”?
I have no idea how to make sense of a unit of energy with no time span…
2 SMA pigtails soldered to a 0402 capacitor
The $$$$ price-tag of a PDN probe is starting to make sense...
FEM simulation of current density (A/m^2) in a 4 layer PCB.
In ParaView, you can set a unique colour for out-of-range data. This makes it really easy to see what areas of the copper geometry have an unacceptably high current density.
I also don't really understand what's happening @ 20 kHz... My first suspect is my fixture, since that wasn't included in the calibration. TBD.
S21 parameters of a 2 port shunt-through measurement
-83 dB = 1.8 mΩ
1.8 mΩ is still ~ 20% error, but
* I don't have a torque wrench yet,
* I haven't done anything to de-embed the fixture from the measurement,
* the CM choke only has -30 dB of CM insertion loss.
I think if I improve each of these points, I can get a lot closer to 1.5 mΩ.
SMA fixture with 1.5 mΩ resistor soldered
I spent the day measuring a 1.5 mΩ shunt to make sure I'm on the right track for low-impedance PDN measurements. I soldered it to a SMA fixture and measured it with a CM choke to reduce braid-error.
When I bring my hand close to the core, I see a change of roughly ±5 dB - pretty unacceptable right off the get-go. I wouldn't have noticed this as quickly without the fast sweep-time of the VNA.
I ran a SOLT cal with the choke inline to see how it would look, and I immediately noticed, even limiting the span to 10 kHz ~ 100 MHz, how sensitive the choke was to cable positioning and de-tuning. It's just some 30 AWG twisted-pair wrapped around a toroid, loose on the bench.
I got my VNA, so I decided to compare the response of this jury-rigged CM choke.
CMT S5045 2 port VNA
New VNA day! 😍
I was going to ask: is Octave insufficient? I haven’t spent time with MATLAB in forever and don’t know Octave well, so I’m genuinely curious.
Showed my roommate how to play Go! Fingers crossed he takes to it; it’s hard to find people to play with in person in North America.
(If anyone plays, hmu!)
When the 2 coax cables you bought for your VNA cost more than your first oscilloscope 🥲
Finally done a design I've been working on for months 😮💨
I’m surely not coming out ahead $-wise by running simulations at home, but even at ~ 200W 24/7, it’s still not my most expensive hobby. However, it’s just that: a hobby. I’m not doing it to save a buck or hide data from Big Brother.
For me it’s more a “love of the game”. A lot of home-labs are running older, less efficient gear to start with.
I like being able to do things like spin up heavy simulations or compilations at home. It’s lower cost compared to spinning something up in AWS, but that’s not accounting for idle time.
I also need to script these measurements. Pen and paper takes a while...
The next step is to build/buy an amplifier and place it between the scope and the DUT. I'd like to be able to test down to 1 mΩ, and injecting 3.5 Vrms (24 dBm) is unacceptable in most situations.
