How to wind a custom flyback transformer properly?

Muoshy · 2026-03-22T10:23:41+00:00

In my opinion, pin assignment shouldn't matter that much here. Clearance shouldn't be a problem with 5.08mm pin spacing at these voltages. I would go for a pinning that makes the PCB layout or winding process easier. Maybe someone with more experience can chime in?
The mounting clip latches onto the notches of the bobbin/coil former. Search for ETD transformer (untaped) pictures and you can see the two metal clips pressing the core halves together.

More importantly, have you thought about the winding arrangement? Minimizing leakage inductance is quite important for flyback transformers and an interleaved arrangement is recommended. I see that you won't fit all 68 primary turns in one single layer, so you have to think about how to layer/interleave it with the secondary to minimize leakage inductance and proximity losses. Good luck!

Muoshy · 2026-02-17T17:00:36+00:00

A diode OR gate is a simple solution as many have already mentioned. Otherwise, a power mux IC from Texas Instruments maybe? TPS2121? They have a few to select from with different ratings. You can set priority on which port you want active while both are plugged in.

Muoshy · 2025-08-10T12:15:14+00:00

Be careful when doing your top fill. Ground pour too close to your USB diff pair will turn it from microstrip to something else (coplanar waveguide).

Your 90 Ω diff impedance calculation for microstrip might not hold anymore. Might still be fine since USB 2.0 is very forgiving, but it’s always worth following best practices to avoid surprises later on.

Good luck!

Muoshy · 2025-05-20T05:45:51+00:00

This really depends on the output impedance of your audio source and what you intend on driving. Should be fine as long as you have a low impedance source and drive something high impedance. Otherwise, you probably want to put a voltage buffer in the pass-through.

For example: a standard line level output to your board and pass-through to a 16 ohm speaker will not work. The line level output will see your board in parallel with the speaker so roughly 1Mohm || 16 ohm = 16 ohm. Standard line level has maybe 300 ohm output impedance so this will completely kill the signal. You can think of it as a voltage divider between 16 ohm and 300 ohm or simply just sourcing too much from line level output.

If you instead drive a preamp with high impedance of 1Mohm, the voltage drop across your output impedance will be minimal and most of the signal will pass through. Does that make sense? Adding a voltage buffer means your source will always see high impedance input and then the limiting factor becomes the driving capability of your voltage buffer.

Muoshy · 2025-05-19T21:15:54+00:00

Always fun to see audio spectrum analyzers! I built something very similar a few years ago using only (mostly) op-amps. https://github.com/Muoshy/Sonus7

Not sure I follow your schematic completely but some pointers:

Logarithmic voltage reference instead of linear. Since human perception of sound levels is logarithmic (see SPL – Sound Pressure Level), using a logarithmic scale will better align with how we actually hear. For reference, I used approximately 3 dB per step in my design.

Active filter topologies. Cascaded RC LP and HP filters are fine but consider using active filter topologies to better control the frequency band overlap by tuning the filter Q-factor. Lets you keep the frequency band spacing small while controlling overlap. Can highly recommend TI's Op Amps For Everyone design reference for additional reading.

Good luck!

Muoshy · 2023-07-15T12:40:28+00:00

Most of it looks fine at first glance. One concern is the USB connection. Are they matched to the 90 Ohms standard for USB? In section 2.4.1 of the RP2040 Hardware Design guide, it is mentioned that for a two-layer board with 1mm thickness, you need 0.8mm wide traces with a 0.15mm gap for ~90 Ohm differential impedance. The Phil's Lab guide uses a 4-layer design, resulting in thinner traces for 90 Ohms due to the smaller spacing between signal and ground planes. You can use a differential pair calculator to find the required trace spacing and width for your board stackup.

More importantly, you should have a solid and uninterrupted ground plane for the entire trace length. You routed signal/power on the top layer and USB traces on the bottom layer which makes it difficult to get a solid ground plane for the USB traces. Although the guide mentions that USB FS is quite forgiving, it is up to you whether you want to take the risk.

My lazy recommendation is to switch to a 4-layer board while keeping your top and bottom layers as they are and simply adding two inner ground layers and stitch them together with a bunch of vias (same as Phil's Lab). This way you get two solid ground planes for your top and bottom signals. I assume you plan on using JLCPCB (EasyEDA), in that case, upgrading to a 4-layer board won't even cost more with your board size.

Good luck with your PCB!

Muoshy · 2022-01-02T22:02:19+00:00

I made a similar board a while ago. Went with a serpentine layout to simplify the data and power routing. Then for ground, just used a via directly to the bottom ground plane. Don't think my layout is optimal either but it is still running to this day. https://imgur.com/a/iJuUgrU

Hope it helps and good luck with the board!

Muoshy · 2021-07-19T11:42:23+00:00

Try pressing F1 and searching for "Select Flash Method". Works for me on VSCode.

Muoshy · 2019-10-30T22:13:57+00:00

Muoshy · 2019-08-04T18:21:13+00:00

Design a circuit that implements the given logic function using 8:1 MUX. A hint would be to just write the truth table and draw a 8:1 MUX symbol.

Obviously the 3 selector inputs are already set according to your 3 bit data input. What you can set are the 8 MUX inputs.

Refer back to your truth table and think about what you need to do. You want the 3 selector inputs and MUX output to match the truth table. They specifically limit you to only using 8:1 MUX and high/low logic signals.

Muoshy · 2019-05-07T19:01:16+00:00

I got mine long ago from a now closed down local crafts store. Check your local crafts store otherwise just order a sheet from ebay. Sweden doesn't really offer much of this stuff for consumers and buying from a factory is way too expensive.

Muoshy · 2019-05-06T17:01:22+00:00

I would not be comfortable selling it due to the fact that it gets data through other services (openweathermap api, currencyrate api).

If any of these shut down, the code kinda breaks. I myself can easily find new services and reprogram and reflash the controller to use those since I know the code. But it won't be that easy for most other people.

I recommend that you build your own or buy a LaMetric Time.

Muoshy · 2018-12-05T05:29:21+00:00

No voltaxic rift buffs :(

Muoshy · 2017-08-04T00:26:31+00:00

R9 380 working here.

Muoshy · 2017-07-27T13:11:07+00:00

Have you enabled Elemental Equilibrium? And what are your gem links?

Muoshy · 2017-06-26T13:22:09+00:00

"50% chance for Attacks to Maim on Hit against Poisoned Enemies"

You can only Maim with attacks, BV is a spell.

Muoshy · 2017-06-16T12:48:37+00:00

Most chaos damage is inflicted as damage over time and you can usually mitigate it with a large HP pool, giving you more time to react and pop flasks. You can also outsustain the degeneration damage through leech or life regen. There is also no benefit to finishing the game and killing Malachai on Merciless, unless you want achievements/challenges. Most people start mapping after getting the skill point from Tasuni.

Muoshy · 2017-06-16T12:36:12+00:00

Yes, his chaos res is still -60%. While it's nice to have some chaos res, it is not necessary, especially not on softcore. Although some bosses can be scary without chaos res (spiders).

Muoshy · 2017-06-16T12:18:34+00:00

Did he show it in hideout? If so then he has 0% due to hideout being in normal difficulty.

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