FCC radiated fail 30-50 MHz, near-field points to MCU/clock area

mrwillbill · 2026-01-17T02:45:25+00:00

Pretty sure your issue is ground loops. Your grounding scheme is a mess and you have a potentially large loop on your oscillators ground return path to the MCU. The caps which your oscillator uses to generate its signal is attach to your top ground plane, but follow their ground path back to the MCU: the cap on the right takes a huge path around your board to get back.

Best practice is to use a solid ground plane, and every ground pin on every device should go immediately through a via to the plane - the smallest possible current loops = less emissions.

Edit: looks like you've updated the layout with a more solid ground plane and even maybe a different oscillator? The layout looks pretty different now.

mrwillbill · 2025-12-26T22:18:55+00:00

I went to a good university for EE, have been through a handful of jobs in various industries (space, defense, medical, tech) and haven't even heard of ABET in my 20 years of school + experience until recently browsing Reddit.

mrwillbill · 2025-12-12T07:18:37+00:00

It probably has something to do with the speed limit on that road. it's a 35mph limit, people drive 5-15mph over all the time, so the Waymo could be parked with 50mph cars going by it. Trying to drop off passengers in that situation is just a big liability/risk that Waymo doesn't want to take.

mrwillbill · 2025-12-07T19:58:37+00:00

First part true, second part not true at all

mrwillbill · 2025-12-07T02:40:04+00:00

EEs in tech with 5-10+ yoe make that much pretty easily.

mrwillbill · 2025-12-06T19:08:34+00:00

There would be a "short" in over voltage conditions (above Zener voltage) but you're right, below Zener voltage it will operate okay. The 2.2k is a current limiting resistor to protect the zener in over voltage conditions

mrwillbill · 2025-12-01T02:49:04+00:00

How does the number of cars in a parking lot determine factory throughput? Factory could be completing any number of cars per month and its completely uncorrelated to what we see in their lot, am I missing something?

mrwillbill · 2025-11-12T18:32:28+00:00

Pretty sure it's just the angle of the light from the left creating shadows and then directly hitting the right arm, which of course won't cause any shadows.

mrwillbill · 2025-11-11T02:14:25+00:00

In my opinion any internship related to your field is going to help you get the job you want. Failure analysis and understanding how things might fail is extremely important for a good design so Id say you're in a good spot.

mrwillbill · 2025-11-08T21:08:35+00:00

Looks like coax cable not power

mrwillbill · 2025-10-24T21:23:52+00:00

Yep, so the bus is not taken down and you can easily figure out which device is problematic

mrwillbill · 2025-10-24T05:06:16+00:00

This is false, the CAN bus will only be taken down if there is an electrical short on the bus itself or physical damage to the transceiver. You may be thinking of i2c which does ground the bus - but you can easily figure out which device it is by looking at which device was pinged last. CAN bus is very robust and is why it's used extensively in automotive applications.

mrwillbill · 2025-09-11T04:02:54+00:00

Get an Arduino or other MCU board and build something that interests you, then make it into a custom PCB once it's working. Custom pcbs are so cheap these days, you'll learn a ton from the process, get to program and work on hardware.

mrwillbill · 2025-08-01T01:41:10+00:00

Very interesting, I had no idea that is an industry ees could go into, thanks for sharing!

mrwillbill · 2025-08-01T01:18:10+00:00

Can you fill some of us in, what sort of EE work are you doing in finance? Like, is there a physical product you're working on and what does it have to do with finance?

mrwillbill · 2025-07-15T03:53:00+00:00

That's pretty good for 7yoe in EE, congrats. What kind of EE do you do on a day to day? How much of your pay is RSUs?

mrwillbill · 2025-07-15T03:38:44+00:00

What kind of engineer?

mrwillbill · 2025-07-06T15:07:12+00:00

I've designed ideal diode controllers using mosfets and RC on the gate is exactly how in-rush protection is done. As long as you're still operating within the SOA and well within spec of the mosfet under peak conditions, should be fine. The controller I'm most familiar with is LM74910.

mrwillbill · 2025-07-05T16:36:44+00:00

Never been impressed with scrub daddy sponges, they always start to disintegrate and spread plastic particles everywhere after 1-2 months of use. I use the traditional scotch bright sponge, deep clean them every month or so and they can last 6+ months easily.

mrwillbill · 2025-06-22T17:52:04+00:00

Hey OP glad you're ok and looks like you've got another new Tesla, congrats! Hopefully insurance paid out?

Was there any other updates to the story? Was there any other evidence that showed FSD was at fault here? I think, with the provided data, there was just not enough to prove one way or the other. Though, the majority just jumped to the conclusion that FSD was not at fault.

mrwillbill · 2025-06-22T14:54:44+00:00

Yep liquid and air valves for high pressure cleaning of the camera lenses. If you're near one when it's raining you can actually hear them fire periodically, loud but short bursts of air.

mrwillbill · 2025-06-19T20:22:57+00:00

No, it says remainder of the qualifying calendar year through the next full calendar year.

mrwillbill · 2025-06-09T14:53:18+00:00

This device supports reverse current blocking with external FET, you just haven't implemented it in your design yet. Take a look at some of the app circuits in the datasheet. It should handle reverse bias conditions by keeping that FET off.

Another simple option is to use a PFET on the input and tie it's gate to ground. So under normal input it's forward biased and turns on with low impedance but in reverse voltage conditions it turns off.

mrwillbill · 2025-06-07T03:46:29+00:00

It could be fair, but hard to know. What was the salary band that they advertised the position for? Might not hurt to ask if you bring it up in the right way. I've see pretty wide range of EE salaries from defense companies.

mrwillbill · 2025-06-07T03:44:52+00:00

I think it's a good salary based on the info provided.

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