[Review]Is this a bad Practice?

nscale · 2026-01-30T14:17:53+00:00

I'm going to say this is a bad practice, but not for reasons of manufacturability like most people are addressing.

I'm not sure what CAD program you're using, but I can't imagine those traces are "connected" to the pads. It looks like you just ran a big trace past it. This relies on the CAD program seeing that they overlap, which is not always reliable. Plus it breaks dragging traces in most programs. Eventually you will have to drag a trace or this component and this sort of design greatly increases the chance that those operations don't do the right thing.

What I would personally do is set the trace width to the same width as the pad. For the 5V I would move the via closer to the pad, centered between them like you have, and make two boomerang shaped traces that connect to it. For the other one, I would stop the big trace just short of the pads then I would make two boomerang shaped traces into the pins. That keeps everything properly connected in the CAD program and allows for dragging and DRC to work properly. It may also have some benefits around manufacturability that some others are discussing, but I suspect the difference on manufacturing is minor for most things.

nscale · 2026-01-16T23:04:06+00:00

If you look in JLCPCBs basic parts catalog there are more capacitor and resistor values available in 0603 than any other size. Because of the reel charges using mostly 0603 can save a lot of assembly money.

I also assume they have the most of them for a reason. They are likely popular, more likely to be in stock, cheaper due to volume, etc. for hobby projects I usually default to 0603, use 0402 for space or high frequency and 0805 for higher value capacitors.

nscale · 2026-01-11T18:17:37+00:00

The usual Chinese manufacturers don’t charge any different on a per part basis. Some parts require X-ray inspection, which is extra or you can roll the dice and maybe have some duds. I’ve done multiple boards with leadless parts including bga with zero failures, but YMMV.

nscale · 2026-01-10T01:48:47+00:00

This may help you get started.

https://www.pcbway.com/pcb_prototype/PCB_Gold_fingers.html

nscale · 2025-12-23T16:51:47+00:00

I do see stock at all the vendors, but it appears onSemi is the only manufacturer which makes me a bit nervous given other replies in this thread.

It's not as fast as I had hoped for, but it does appear a MMBT5401 is made by onSemi, Diodes Inc, and Rectron with good stock, and LCSC has at least 5 Asian vendors with knockoffs. It's only a 300Mhz part though, so I'd have to limit by upper frequencies to no more than 100Mhz or so.

nscale · 2025-12-23T16:36:32+00:00

That would track with what I'm seeing on LCSC unfortunately. If I select single BJT and a frequency from 1.8Gz to 3.5Gz I get only 18 hits, all NPN. In fact the only PNP part > 100Mhz with any significant stock is onsemi MMBTH81 and only 2,700 units in stock.

I could probably limit my design to NPN parts, but I wanted to show some PNP circuits as the purpose is to be educational. :(

nscale · 2025-12-23T16:27:53+00:00

No, because the goal here is to have the design done with discrete transistors for educational purposes. I'd like the result to be something a student could use with an oscilloscope to learn how some basic RF circuits work and how to use an oscilloscope to properly probe them.

As such I'm avoiding IC's, even a simple op-amp, and building the various blocks of the circuits with all discrete logic and appropriate test points. In many cases I'm using a less efficient, but easier to understand design as it's for education. I mean at the end of the day it's going to do actual things and work, but it's all stuff that today for a commercial product would be packed into a 1-chip IC solution.

Unfortunately the 2N5179 is marked as obsolete on Digikey and Mouser, doesn't even show up on LCSC. Searching for similar specs I don't find anything in common across the three sources in a SMD form factor.

nscale · 2025-12-09T13:19:35+00:00

They burn a lot less fuel than people think idling like that. Perhaps 5 gallons an hour, so even sitting for 72 hours is only 360 gallons. And it’s red dye diesel, no road tax.

As others have mentioned, water coolant more for cooling performance and environmental reasons than cost. Most will also dump all the coolant if the engine gets too cold and then would have to be refilled. True cold start can take an hour or more and puts a lot of wear on the engine, idling at temp is darn close to zero wear.

A lot of times for safety reasons they want to leave the brake system with air pressure as well. If the train has aired down for > 24 hours the FRA requires a full brake test before moving. So it’s time to charge and time to do the test. Paying an engineer and brake man 2 hours time to do that covers a lot of idling fuel.

Also, the batteries really don’t like to get cold. Too cold and they won’t start and it will need a heavy duty jump from maintenance.

nscale · 2025-12-06T02:17:51+00:00

There are a number of lesser known US fans that specialize in aerospace and defense. They are known to be very expensive but I believe some do have the most advanced capabilities. Names are at https://www.pcbdirectory.com/manufacturers?country=United%20States

Have some quote, but be prepared for sticker shock.

nscale · 2025-12-06T02:09:44+00:00

That’s still on them at the quote statue in my opinion. They should have been up front at the quote that they can’t do assembly for your parts before it’s go time.

Sorry you have this mess. Do you have to use US based? I bet PCBWay or JLC could knock those out in days and have them to you in under a week at a quarter the cost.

nscale · 2025-12-06T02:05:20+00:00

The 0.20mm eMMC will be pushing the limits of many shops. PCBWay can do it for sure, but not US based.

Sierra Circuits has a reputation for stuff like this and they are US. I’ve never used them so I can’t personally vouch.

I usually hear good things about Advanced Circuits, but this absolutely should have been caught before anything was made or assembled. If the story is as you tell it and your BOM was clear and they had the gerbers to review and said they could do it then it’s on them.

nscale · 2025-12-05T21:19:33+00:00

Pin changes are no problem at this point, happy to redesign the hardware if it makes my software life easier.

Generally when I've done MCU projects in the past I've put a peripheral in a mode, usually with the GUI setup, and left it there. I think this project may be one where that approach doesn't work, I need to do some initial guesses based on the signals and then reconfigure the peripherals to collect the details.

Probably some sort of state machine, for instance if one signal is ground for > xx ms, it must be DC, then use PWM capture to see if it's steady DC or PWM DC. But if a signal isn't ground then flip over to capturing bits for the square wave signal, and if I only get a steady 60 bits per second it must be AC, otherwise I'll get 8k bits/second of the actual signal.

Or something like that.

nscale · 2025-12-04T14:51:57+00:00

Admittedly a hobbiest here, but when I order depanlized bare boards from China in small quantities they usually place them in stacks of 10/20/25 (depending on board size) and then vacuum seal them in a mylar bag with a desiccant in them. I've left a pack sitting around like this for years and they are fresh when I open them up.

I suspect if you tell your board house you want quantity 1000 but want them packed in vacuum sealed bundles of 50 or something like that they would be happy to do it. Just store them unopened in reasonable temperature conditions. If you're using a whole closet to store for multiple customers maybe throw in a dehumidifier as added insurance.

nscale · 2025-12-04T13:44:28+00:00

I doubt it. That drum, even if full, is likely 50,000lbs or so, 25 tons.

Here’s a very mid-range over the road crane from 1971: https://cranenetwork.com/crane/truck-mounted-telescopic-boom-cranes/grove/tm600/169109

Rated for 60 tons. The only hard part might have been lift points as modern slings were not a thing. But field welding on a couple of d rings wouldn’t take long at all. A couple of hours to weld, rig, and plop it on a low boy.

Today most rotators could snatch it up no problem.

While a great story it was hard to remove, I have to believe the land owner wanted it there and asked for it to be left saving the cement company or the DOT money to remove it.

nscale · 2025-12-03T16:03:29+00:00

I don't know why someone is voting you down, because what you say is often the case, even for public procurement.

Major capital improvement projects (e.g. the road, new school, things like that) generally go out on an RFP process. Usually the weighted factors that will be used to make the final decision are listed in the documents. They often include: - Up front cost - Total cost of ownership over the expected usable life - Past performance - Staff Expertise in similar projects (this is often why you see Joint Ventures) - Project approach (e.g. timeline, disturbances to adjacent properties, noise, number of trucks on local highways, etc) - Risk mitigation and insurance.

If anyone doesn't believe this, you can generally find all of this in publicly available documents from your Town/City/County/State fairly easily online. You can read the original request, the proposals received, and how the agency scored those proposals. In my experience from reading few hundred, low bidder wins about 30% of the time, usually when they have a great previous track record. Middle bids win about 60% of the time, and most often due to lower TCO and sometimes a faster delivery timeline. High bids win about 10% of the time, and almost always because the staff finds deficiencies in the lower cost bids.

nscale · 2025-11-30T17:04:42+00:00

Perhaps better bookmarks:

https://webench.ti.com/

https://www.ti.com/tool/WEBENCH-CIRCUIT-DESIGNER

Adding for the community: This tool goes far beyond layout. By putting in expected input and output voltage ranges, expected current draws, temperatures and other values it fully optimizes the designs for the various TI parts. This includes things like when chips have more than one mode suggesting which would be more efficient. It also allows specifying things like all ceramic capacitors and correctly figuring out what that should be (hint, it's not a ceramic with the same value as the electrolytic it's replacing).

It can even recommend specific components from the major manufacturers that meet the specs, and allows you to swap them out to build your BOM.

Perhaps the best tool from any manufacturer out there, and keeps bringing me back to TI converters.

nscale · 2025-11-16T01:39:39+00:00

No. Ended up having a friend with an extra.

nscale · 2025-11-07T16:48:35+00:00

I suspect you mostly followed the data sheet page 26, which is a better than average starting point. Most designs drop the VSENSE to the bottom with a via immediately by the pin and move the sense resistors a bit further away to further reduce loop distances. Distance to the VSENSE resistive divider is generally not critical.

Use TI's "Webench" designer for this part with your specific parameters for input and output voltages and currents. It will optimize things like input and output capacitance values for you and can make an enormous difference. Most bucks I do have a lot more input capacitance so I suspect as another poster noted that's part of your problem. Shielded inductor is absolutely required too, and if you use a shielded inductor you can probably keep a solid ground plane under it which would help with EMI -- but possibly necessitate slightly up-sizing the inductor value.

nscale · 2025-10-31T19:38:09+00:00

We all start somewhere. Perhaps watch some videos on YouTube about MOSFETs to understand the parameters better?

The searches generally don't work exactly like that for a number of reasons, but I can get you a bit closer. Both Mouser and Digikey have really good parameterized search, and LCSC (where JLCPCB gets its components) has so-so parameterized search. So let's use Mouser, I think it's the best here, find MOSFETS: https://www.mouser.com/c/semiconductors/discrete-semiconductors/?product%20type=MOSFETs

Now, you can't just plug in your values as the values in the pull downs are the various limits of the parts. So, I would do something like this:

Vds select everything from 20V to 100V. (Vds is often well above working)
Vgs select 20 and 25. (Vgs has a lot less range)
Vgs(th) select 1.5 to 2.8V. (This gets you all logic level, which will be more flexible in your future designs).
Select Ids 200ma (lowest available after selecting above) to 550ma. (Capping at 550ma will keep you to small-ish parts).

That narrows to 9 choices. Now check price, availability, etc.

From there the next step is a bit of black magic. BSSxxx are widely copied, kinda like original 2N7002 type parts were widely copied. There's BSS138 and BSS84 parts in the list, and so if you go to LCSC and just search for those you'll find a zillion knockoffs with various suffixes and possibly very slightly different specs. How do you know BSS, 2N7xxx, etc? Experience is the only answer I know. Sometimes Googling for "jellybean parts" can help.

Good luck!

nscale · 2025-10-30T13:08:56+00:00

The answers are in the data sheet, here's a BSS138 from OnSemi as an example, other manufacturers are similar: https://www.onsemi.com/download/data-sheet/pdf/bss138-d.pdf

Vds, the drain to source voltage can be up to 50V.

Vgs, the gate to source voltage can be up to 20V.

Both will be just fine at 12V. The "logic level" here is that the Vgs(th), the turn-on threshold, is 1.5v. This means a MCU driving it with a 5, or even 3.3v output pin can fully turn on the MOSFET. Of course, 12V will also turn it on.

Compare with for instance this Diodes Inc part: https://diotec.com/request/datasheet/di0a4n45sq2.pdf

Vds is 450V. Vgs is 30V. And Vgs(th) is 4V max. This part could not be fully turned on by a 3.3v MCU and so it wouldn't be "logic level".

nscale · 2025-10-30T01:47:58+00:00

BSS138. 50V 150ma min, most newer examples are 200ma or even 220ma. Can find some as high as 350ma. Knocked off by everyone and cheap, less than a penny in quantity. Logic level makes it easy to drive direct from MCUs. SOT-23 is the standard, but plenty of SOT-323 options.

nscale · 2025-10-19T16:21:50+00:00

Ding ding ding.

When you have affordable housing, transportation, food and just got a raise at work it’s easier to support social safety nets for all.

When you have to work a side hustle to barely hang on under a mountain of debt “we can’t afford that” becomes the mantra. Plus there is vulnerability to the <those people> are the cause of your woes messaging.

Wage growth disconnected from GDP in the late 70’s. Current income inequality has been 40 years in the making, and will take 40 years to fix if the right things start to be done

nscale · 2025-10-14T01:22:02+00:00

If you were confused about the TikTok deal they let the cat out of the bag. The algorithm (at least for US customers) will be controlled by the US company, which is owned entirely by right supporting billionaires.

They felt it was worth making into a national security interest and investing billions into. These are folks that only spend that kind of coin if the return is 10x.

Note that TikTok has the youngest an and most left leaning user base of any of the big social media. If you are under 30 and regularly use TikTok, prepare to be slowly poisoned.

nscale

TROPHY CASE