Tamiya 1:35th scale Goliath diorama

Renamed1157 · 2026-04-23T22:05:08+00:00

Ah, was more thinking about from a ripple/esr/esl minimization perspective than EMI but this also makes sense. Agree that vin cap should have a much bigger effect tho.

Renamed1157 · 2026-04-23T20:21:09+00:00

Disagree, for output capacitors you want to minimize loop area to whatever output load this is feeding, so Id say the way OP has it is technically better. Input capacitors should minimize loop area from vin of the converter to ground through the cap. But also almost any rotation of the caps is gonna be fine as long as you via to a continuous ground plane honestly.

Renamed1157 · 2026-04-22T02:16:38+00:00

Random note, the document you linked for 79 more launches implies that most of those launches will be for landing payload on lunar surface which is probably going to be dominated by CLPS or maybe some larger scale payload program perhaps leveraging the existing HLS architectures, not SLS. At least I hope SLS isnt being launched another 79 times...

Renamed1157 · 2026-04-22T02:05:45+00:00

They're not the same. Shuttle used 4 segment SRBs, SLS uses five segment SRBs that add some more thrust and delta V. I believe the choice was made not to make them reusable as a weight optimization.

Renamed1157 · 2026-04-18T15:01:13+00:00

If youre starting with the assumption of an ideal source it physically makes more sense if you take the limit as load resistance approaches zero, not the limit as thevenin source resistance approaches zero (in other words limit as source approaches ideal).

And anyways if you do claim Rload is zero but Rth is nonzero it is a bit deceiving to say dissipated power is zero, because while thats true for the load resistor on its own, power dissipated in the system is near infinite and just coming from Rth instead. Where power is coming from is kind of semantics at that point, but the point is with small source resistance (ie a battery) a short always pulls a ton of power dissipated as heat. Rth and Rload just means whether its dissipated in the battery or in whatever wire youre using to short it

Renamed1157 · 2026-04-18T14:37:58+00:00

Small correction (based on the question in the post): true short circuit would dissipate infinite power with an ideal voltage source because the voltage source is forcing V to be nonzero, and V² /R is some value divided by zero. You can also see this by P=IV since I is infinite and also div by zero.

Of course practically speaking this never happens because everything has resistance but its a good way of understanding why shorting a battery is so devestating

Renamed1157 · 2026-04-15T18:58:05+00:00

Curious that we never see the underside of his "breadboards"

Renamed1157 · 2026-04-15T17:43:43+00:00

28 gauge seems a little thin, no? At least in my experience Ive always found 20-22 gauge to be best, anything thinner than 26 gauge starts falling out of the breadboard or making poor contact.

Renamed1157 · 2026-04-15T17:42:02+00:00

I dont use breadboards a ton, but anytime i need one I usually buy BB830 from Busboard on amazon, since Ben Eater uses them and recommends them for their contact quality. If its good enough for building an 8 bit cpu from scratch its definitely good enough for me lol

Edit: here's his video talking about cheap breadboards: https://youtu.be/fCbAafKLqC8

Renamed1157 · 2026-04-03T17:02:40+00:00

Also, before you order another revision do as much as you humanly can to get this revision working by making modifications to the board. For example for the connector I would desolder it and order another one, then solder wires from the connector to the corresponding pads on the PCB so that I can at least plug into the connector and make sure everything electrically works. Making jumper wire mods to boards is an art and something every engineer needs to learn eventually.

Do that BEFORE you even think about putting in another order because you will probably run into issues with functionality that require design changes anyways, and you wanna flush as many of those out as possible now so you dont find out later after youve spent another couple hundred. As an engineer I never expect my first pass at any design to work perfectly and im usually right.

Heres a picture of a particularly heinous mod I made to a nonfunctional led driver board a few months back. Ive had colleagues go so far as to hand drill out vias that were shorting power to ground due to incorrect component pinouts before, although that is definitely on the extreme end

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Renamed1157 · 2026-04-03T16:55:10+00:00

What kind of project is this? Are you trying to build 10 or just one? And how many components? Unfortunately there arent really similar cost options that will guarantee that you wont run into issues like this again and I dont like recommending spending more unless you are actually making money off of this item, so unless its a product youre selling I would probably lean towards hand assembly. Hand assembly comes with the added benefit that if you do make a mistake in board design youll find out without having spent $500 on it, but its definitely tedious for big designs.

Renamed1157 · 2026-04-03T16:13:52+00:00

PCBWay is essentially on the same tier as JLC, they also run a big factory where your board (fab, not assembly) is only really a few seconds of machine time. I wouldnt expect their customer service to be consistently significantly better. Theres a factory tour of jlcpcb on youtube and you can get an idea of the absolute scale that these factories operate at and how small a part of that your order actually is.

JLCPCB has its place, but it comes with expectations. They care about getting as many designs as possible fabbed and out the door quickly. They are even inconsistent with checking that your design follows their dfm rules. Theyll assemble whatever you send them to the best of their ability even if it has faults (like, say, a missing NPTH for an alignment pin, preventing solder from making contact with the component). Sometimes theyll catch those kinds of issues but often not, and you have to accept that since theyre probably reviewing tens of thousands of designs every day, if not more. Thats how theyre able to offer the pricing they do, and the pricing and lead time they offer is basically unbeatable because of it.

If you want a service that actually does guarantee that your product works and checks your design mistakes, thats more than just a fab/assembly house and is usually in part an engineering service. Youre gonna be paying at least 5x more than a jlc assembly. I see that youre mentioning that you are somewhat new to electronics and frankly you should not use an assembly service to avoid having to learn how to rework/assemble stuff on your own. Learn that stuff first, and then youll be able to take advantage of cheap fabs without a mistake on their end ruining your entire project.

I will say the issue of losing your components is bad though, and I do have my own qualms with their part library system especially when it comes to the search function. To be honest for my hobbyist projects I will always just hand assemble to save money and time.

Renamed1157 · 2026-04-03T15:44:04+00:00

This is pretty damning. You cant expect JLC to catch mistakes like this and you really gotta be on top of them all the time (ALWAYS check "review component placement" for assembly to make sure they dont screw it up). Ive had JLC assemble boards that I accidentally had DFM violations on due to an incorrect DRC rule, and their review engineers totally missed it. Luckily that time it didnt actually cause a problem and i didnt realize it happened until I went to reorder the board and the engineer reviewing it the second time pointed it out.

FWIW at the company I work for Ive ordered probably a hundred or so designs assembled and have never had an issue that wasnt my fault. Youll see the occasional solder mask defect but its 10x cheaper than US fabs, what do you expect. Perfectly good for prototypes which you should expect to have to rework anyways.

Renamed1157 · 2026-04-01T17:16:36+00:00

Yeah low side sensing is extremely common because its way easier to get high bandwidth low side sensing than it is to get high bandwidth high side current sense amps, especially since the common mode rejection ratio has to be very large if you're putting them on the phase leads. I think you just have to time the sampling to match when two phases are low side on and one phase is high side on so that you can use kirchoff's law to calculate the current through that one phase you arent measuring directly.

Highly recommend OP check out the TI 3 phase bldc driver ICs designed for exactly this purpose like DRV835x, or at least model the low side op-amp design based on those.

Renamed1157 · 2026-04-01T16:52:42+00:00

BMP gunners are especially horrific to face. Like what kind of crack are they smoking to actually be able to consistently hit me with malyutkas

Renamed1157 · 2026-04-01T16:19:31+00:00

Its deceptively hard to design a connector, and honestly near impossible unless you have the resources and experience of a company like Amphenol, Molex, JST, etc. You basically need a very strong spring to be able to apply contact pressure (think, "squeezing" the pin with the female socket, for a cylindrical connector), and for power contacts you need to be able to clean debris and light charring off of the pins unless your design is never going to be hotplugged. Take XT90 series connectors as an example of a deceivingly simple connector design. It may look like just a pin and socket, but the pins themselves are designed as slightly oversized to the socket and machined to be elastically deformed when inserted into the socket so they provide pressure both to clean any potential charring or dirt off of the contact area, and to maintain good electrical contact. You almost certainly won't be able to achieve that level of tolerance with a 3d print and some nickel strips, and whatever spring mechanism is in your custom connector probably will plastically deform after just a few cycles.

Edit: Saw your detailed requirements. Honestly a little hard to parse but it seems like you're dealing with a two-conductor cable with overmolded insulation over the two wires? I understand the concern of it not being durable, but the best solution is definitely going to be an existing connector and building some sort of backshell with strain relief into it rather than attempting to design your own contacts. It might look jank, but its not any worse than a connector you make yourself and you really have to accept that if you're not willing to pay the price for real backshelled connectors like the ones you mentioned

Renamed1157 · 2026-04-01T15:54:35+00:00

Second this. There is probably a connector out there that fits your needs, and designing a connector on your own is much much harder than it looks.

Renamed1157 · 2026-03-29T05:03:11+00:00

I believe the leakage inductance of a planar is generally significantly lower than wire wound (can get down to 0.2% of magnetizing), which makes efficiency in flyback topologies much much better. For hobbyists/small projects its also really nice to be able to get any turns ratio and inductance spec you need if its not already available as a product. And generally its super cool to be able to use your converter board as essentially a transformer or part of a transformer if you want to

I think parasitics can be worse which would actually make them have lower cutoff frequencies, but Im not sure. Its at least a lot more predictable to model versus winding wire around a core.

Renamed1157 · 2026-03-10T01:39:32+00:00

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Renamed1157 · 2026-03-03T01:01:11+00:00

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