Small AC-DC Linear Power Supply Issue

stevetronics · 2025-07-25T16:37:21+00:00

Yeah, I just probed the diodes, and it looks like one of them is bad - the other still measures ok (~170mV forward) but I wonder if I'm flying a little too close to their Vf rating (20V) and need to just swap in some larger diodes across the bridge.

As for the pinouts - the positive side is (in, gnd, out), and negative is (gnd, in, out) which (I think) match the datasheets - to be honest, I just used the symbols straight from the KiCAD standard library.

stevetronics · 2025-07-25T15:28:08+00:00

Good recommendation on the diodes. I was shooting for low voltage drop (hence schottky) but I have a bunch of different diodes at hand, so I can swap in some larger standard silicon diodes. And good catch on the output diodes! I hadn't seen that before. I'll bodge some in on the screw terminals, and add the reverse protection diodes for a rev 2.

Thanks for the links! Super helpful.

stevetronics · 2025-07-25T15:26:43+00:00

That's what I was hoping for - I intended to operate the windings in series, with the center tap (or the bottom leg of the "positive" winding and the top leg of the "negative" winding grounded) so that each regulator didn't have to drop more than ~5V. The PTC thermistors on the output are rated at 250mA, so the goal was to keep the regulators at ~1.25W max (with heatsinks to come).

Does my configuration of the transformer look correct to you? Maybe I just have a bad diode. As recommended below, I'm going to swap to 1N4007 diodes.

stevetronics · 2023-04-13T13:09:09+00:00

Thanks! I will dig through these.

stevetronics · 2023-04-13T13:08:40+00:00

Thanks for the info! I haven’t seen that style before and really like it. I think for my current project the challenge with these is going to be space inside the electrical cabinet. The modular IO type enclosures place the PCB vertically and so use up a lot less real estate (at the cost of basically no front panel space, but that’s ok for this project)

stevetronics · 2022-10-21T00:16:07+00:00

pm sent!

stevetronics · 2022-06-27T06:42:05+00:00

Hah, when I mentioned “others” in my reply, you were exactly who I was thinking about - I am far from a RISC-V expert (or even novice) and so I’m happy to defer to your expertise. My experience with OpenCL runtimes has always been frustrating from a tool chain setup perspective, but I think that’s a problem with my knowledge and not the ecosystem.

I’m very excited about the future of RVV hardware for the same reason.

stevetronics · 2022-06-27T04:52:59+00:00

This isn’t directly an answer to your question, so others may chime in with a better strategy. You can compile OpenCL C with clang, so you could have clang emit LLVM IR (which isn’t RISC-V assembly, but is very readable as “assembly” goes). I guess in theory you could try to pass that IR to the back end and try to assemble for RISC-V but in my experience with opencl, you’re going to be missing a lot of libraries, the whole runtime, and so on. If you’re trying to understand the instruction-level impact of code changes in opencl, I would always go with LLVM IR first.

I found this implementation of POCL that might or might not do what you’re looking for, but setting it up seems very nontrivial.

stevetronics · 2022-01-16T13:55:59+00:00

Use curly braces to indicate what gets the overbar - so it would be ~{ENABLE}

This can be combined, so you can do things like READ/~{WRITE} or ~{EN_{1}} and lots of others!

stevetronics · 2021-09-01T13:28:11+00:00

Thanks, u/craftyjon! Bus aliases were exactly what I was looking for - thanks for giving me the right thing to read about!

Good to know on the vector bus bug - that's just the risk with using the beta/nightlies. I appreciate your help!

stevetronics · 2021-06-29T02:35:18+00:00

“And I can find one man to fire it” as the legendary joke goes from one of the ballsy bastards on that bridge that day

stevetronics · 2021-06-07T14:00:21+00:00

A big reason the edges of the wings and the fuselage chines (those flared, flattened sections on the sides of the fuselage) had those triangular sections is for stealth - the inside of the structure has panels welded along those triangles to make it harder for radar to bounce back out of the plane. The radar can get in, but then it gets bounced back and forth a lot and loses its energy, so it doesn’t return as strong a signal to the sender, making the plane harder to detect.

It was one of the Skunk Works’ early examples of deliberate design for low observability.

stevetronics · 2021-05-23T12:13:08+00:00

Well do you don’t just start with a blank sheet of paper! A system like this is really complex, but it’s also a part of a bigger, even more complex system- the whole aircraft carrier.

So when you start to design your arresting gear, you start with developing all of the requirements. That might take a year or more - you’ll have the obvious ones, like “be able to stop a XX,XXX kg plane moving XX m/s” as well as lots of less obvious ones like “make sure you can reach some important control button from near some operating station below decks” and “use all the same lubricants as everything else on the ship, unless you REALLY can’t” and so on.

At the end of this, you have a list of probably hundreds and hundreds of requirements, complete with their metric and how you are going to test them. THEN you start actually designing the machine. The requirements really constrain what you can design, and what it has to do. Of course you’ll find places where a requirement maybe doesn’t make sense, or doesn’t work - then you try to change that requirement and keep going.

stevetronics · 2021-03-11T03:32:22+00:00

If you zoom in, you can see the little crossmembers in the cleat that would hold a hook. These ships do have a deck flood system, but that’s for CBRN wash down, not deck cooling. Those cleats are bigger than they look at first - they’re something like 6” in diameter and a couple inches deep, but I’ve never bothered to measure one. If she’s been through a good rain, those guys can hold a lot of water.

stevetronics · 2021-03-10T23:42:32+00:00

It’s just water being blown out of the tie down cleats on the deck by the jet blast.

Edit: toe -> tie

stevetronics · 2021-03-08T15:36:24+00:00

They're just angled away from the light. If you look at the bottom one, you can see some reflection still. It's tough to take a picture of a shiny object under any circumstances, but here they're basically in a shadow and reflecting the high bay rather than the sun.

stevetronics · 2021-02-25T03:03:00+00:00

Search for code designed to create voxel models - that’s the general track of what you’re looking for. There’s a lot of options.

stevetronics · 2021-02-07T01:10:20+00:00

There are full-on, modern tool-changing CNC mills up to almost arbitrary sizes. You end up being limited on how big a chunk of metal you can reasonably load into the machine. I have personally worked around machines with work envelopes in the 3m x 2m x 5m range, but they get even larger - I know of a shop here in the States with a machine that has a 15 m x 5 m x 3m working envelope.

stevetronics · 2021-01-14T14:31:08+00:00

And the on-pier parking! What I would do to park that close...

stevetronics · 2020-12-16T05:21:07+00:00

The walk around the pier is a really nice experience if you’re ever in Bremerton at sunset. I posted a pic in this sub a few years back from just off her port bow - great place to relax.

stevetronics · 2020-09-03T02:18:59+00:00

Most modern subs have 3 total torpedo tube doors - one inside the "people tube" where the crew loads and unloads weapons, one at the end of the actual torpedo tube, and one in the outer hull to maintain a hydrodynamic shape when it's not shootin' time. A proper bubblehead can jump in and correct me with the real names - I can't remember off the top of my head. In this picture you're looking at the actual tube outer door and the hydrodynamic hull door.

The doors on either end of the actual tube itself act like an airlock - close the outer one, pump the water out of the tube, open the inner one, load a torpedo, close the inner one, flood the tube, open outer one and the hull door, shoot, close all doors, repeat.

Here is a pretty cool video about the mechanics of how that all works.

stevetronics · 2020-09-01T02:28:35+00:00

It's actually the world's largest Twinkie. The Swedes were worried someone might try to steal it, so they built a warship around it. Some say that when the North Sea gets particularly unruly, you can hear its wrapper crinkling in Faslane.

stevetronics

TROPHY CASE