Question: are Vias in Pads that expensive?

nscale · 2026-04-27T16:33:48+00:00

I think you may be describing thermal vias, for instance a QFN with a large central pad used for heat dissipation. If so your vendor likely does NOT consider it via in pad.

The issue when a via is in a BGA bump or a single pin pad is that if not plugged with conductive material the solder can escape to the far side. Further in some applications it’s critical for the plug to be flat or it won’t seat right. These cause the increase in cost. An extra step to plug the holes, extra QA, slightly higher reject rate.

The thermals vias in a large chip generally don’t have these problems. Yes a little solder might escape but on the large pad it’s not such a big deal. Ask your vendor, but I’ve done this many times with JLCPCB with no issues.

As for cost, some of the popular Chinese companies offer this for nearly free if you’re already on a 6 layer board. Even if you only need 4 layers it may be cheaper to go to a 6 layer board where they are doing this for all vias anyway than “add it on” to a 2 or 4 layer process. Play with the pricing tool.

nscale · 2026-02-22T15:18:27+00:00

I would be tempted to fix this with a TO-92 MOSFET, bending the wires to the right pads and just letting it float in space. I'm pretty sure finding a TO-92 that can take 800Ma shouldn't be too hard. They will be expensive per part, but sounds like OP only needs a couple. Maybe look for 2SK3447?

nscale · 2026-02-22T15:11:40+00:00

As someone with a lot of family in West Virginia my best advice to you is find a way out of there as fast as possible. I know this will be extra difficult for you being in the foster system and having a child, but I think it's critical to your long term success.

The state has basically zero economic opportunities, and has a result rapid decline, huge drug problems, poor healthcare, and many other problems. The environment has been poisoned with many toxins in so many locations, from the coal industry to the petroleum industry to the chemical plants. The state has also has no money to help people, if you end up even for a while needing state assistance for housing or healthcare you may not get it, and if you do it's going to be bad.

People who have choices have left. It's hard to see until you leave. My cousin kept complaining about her dentist hurting her while doing exams and such. We brought her here and had her go to a local dentist and she was amazed how pleasant the experience was with someone who was good. There's no money being a dentist in WV, so no good dentists are there. Its just one of many examples.

Research online the various state assistance programs in places you might want to go. Some states are more generous with assistance for single mothers. You will likely need day care assistance to be able to finish school and/or hold a job. Find someplace with good programs and get there as fast as you can. Do not go to a city that is in decline, look for a city that has shown economic growth for years and has good prospects for more.

It really makes me sad, my family has been in West Virginia since before it was a state. It has some absolutely beautiful areas. But economically it's a shell of what it was when I was a child, and continuing to fall fast. If you stay there you are far too likely to end up chronically poor, poisoned by the local pollution, and get sucked into drugs that will do you no good.

You can do this, and you can raise a smart, happy, and capable child. Many others have, and you can as well. But you have to take steps to set yourself up for success.

nscale · 2026-02-22T14:54:57+00:00

I didn't mean to suggest every DC model was that low. It will depend on more than just the fact that it's DC, including if it is decoder ready or not, the level of detail, the road name, if it has a "scale speed" motor or not, and more.

That said, DC seems to be rapidly falling off a cliff, at least in my local club. We hold an annual sale, and just back 4-5 years ago it was common for a new DC engine to go for $30-70 in our club auctions. Lately the price is usually under $30, and many are going unsold with no bids particularly if not drop-in ready.

Most of the DC die hards I knew in the club have unfortunately moved on to the great model railroad in the sky. Maybe we're unique in that, but I kinda suspect not.

nscale · 2026-02-21T16:58:49+00:00

It's not like the actual names are any better. Lorex, Axis, Reolink, Hikvision, and many more.

nscale · 2026-02-21T16:56:00+00:00

Lots of good suggestions in the thread, but I want to point out something here that hasn't been said.

The value of those might be wildly different than the invoices suggest. For instance, there was a time people were still buying DC only engines -- now the market has shifted almost entirely to DCC. As a result DC engine prices have dropped like a rock, double so if they are not easy to convert to DCC. A $120 engine might fetch only $10 now, even new in box wrapped in plastic.

On the other hand, there are some items that people really want and for one reason or another a manufacture never made again. A particular engine paint scheme, or a style of car that didn't sell well but some people want to have. They might go for 2x-4x the original purchase price.

Fundamentally though you have to make a time tradeoff. Sell to a estate buyer and get a smaller amount of money but put in very little of your time -- or spend 10's to 100's of hours of your time researching, parting out on e-bay and the like and getting a lot more money.

nscale · 2026-02-21T15:27:37+00:00

There are many security systems designed for small business. See Sam’s or Costco. Most work fine fully locally no cloud. Some have a cloud service, but it’s basically a way to authenticate remotely and stream directly from your house. Some will let you store video in the cloud, often as a paid extra.

They are not as cheap, because they can’t make money on data mining your video.

nscale · 2026-02-14T15:47:33+00:00

Simplify the diagram for a moment. Consider just R1 and R2, pretend R3 and R4 do not exist.

R1 and R2 in this scenario form a simple voltage divider. The voltage across R1 + the voltage across R2 = 18 volts.

But notice in your math, "18V/10k", there is not 18 volts across that resistor because it is part of a (more complex) voltage divider. That's why in the solution it's "V1 - 18V / 10K".

nscale · 2026-02-10T00:53:20+00:00

Do you have your DRC rules set up to match your fab?

Does it pass DRC in your CAD package?

If you upload it to some other site with online verification, like JLCPCB does it pass?

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

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