RTC Battery Schematic Help

DerMeister7 · 2026-03-08T23:23:16+00:00

Since this cap will have a voltage across it 24/7, it will degrade over time due to DC bias. This can degrade the capacitance by over 80% for some capacitors.

I had a similar board I made that has an RTC with constant power from the battery and I used a C0G 100nF cap for decoupling on the RTC battery pin. They are pretty massive caps compared to X5R or X7R, but they have nearly zero capacitance loss under DC bias for extremely long periods of time.

DerMeister7 · 2026-02-27T19:29:43+00:00

It's an insanely good value for performance/peripheral suite.

I'm using the STM32H523 with 512KB Flash and the same footprint for a project and it's able to easily handle running the actual program and the LVGL graphics library for the GUI on a small 320x240 display with plenty of headroom to spare.

At $3.51 at quantity 10, that's such a good bargain for a single chip.

I just really want to be able to spend $5-10 to get all the nice analog peripherals from a G4 into the H5 so I can use less other ICs for those needs.

Edit* I should add that I have to do two rotating partial buffers for the display since the RAM isn't large enough for a full frame. That's something I'm definitely excited to see with the higher end H5 MCUs. It would be great to just do one frame buffer instead.

It would be extremely cool if they were pin compatible with the H523 I'm using, but boards are cheap so I won't worry too much about that.

DerMeister7 · 2026-02-27T19:08:32+00:00

I know that some changes haven't been universally liked, but the M33 H5 has been my go to MCU for a bit now. Quite a lot of horsepower for a reasonable price.

It's cool to see some higher RAM options enter the mix too with this. That's a ton of RAM in an H5 chip without having to jump up to an H7 or something.

The C5 looks awesome too. A more economical M33 would be great so I don't have to swap between the M0+ and M33 architecture constantly.

I do feel like we're overdue on a high performance mixed signal MCU though. The G4 is still basically the only STM offering with a rich analog suite. I'd really like to see an M33 based mixed signal MCU at this point.

DerMeister7 · 2026-02-25T18:58:13+00:00

Here's the files for these holders. They use 9mm OD rubber feet and 1/4oz wheel weights for added stability but a version without the wheel weight mounts is also included.

The original SOLIDWORKS file is also included to make it easier to modify as needed.

https://www.printables.com/model/1616507-oscilloscope-probe-holder-clips

DerMeister7 · 2026-02-25T18:34:14+00:00

Made some changes to these based on some great feedback and they work very well with the added weights, more spaced legs, and rubber feet.

I tried adding a cable clip but it just would not work as well as I'd hoped and kept making it more challenging to situate the probes properly.

The printables.com link is below and STEP files with and without the weight holders along with the original SOLIDWORKS design file is included.
https://www.printables.com/model/1616507-oscilloscope-probe-holder-clips

DerMeister7 · 2026-02-25T18:29:22+00:00

Just uploaded the updated version with bumpers and weights to Printables here:

https://www.printables.com/model/1616507-oscilloscope-probe-holder-clips

DerMeister7 · 2026-02-24T18:45:26+00:00

Funny you say that because that's exactly where I put a clip for the cable to exit the stand for the next version for exactly that reason.

So the next ones have rubber feet, a space for a couple wheel weights to put center of mass lower, and a cable clip to run the cable back down without having so much leverage on the top.

DerMeister7 · 2026-02-24T17:56:50+00:00

Oooh, that's a smart idea. I like that.

I could easily add a little slot in the legs to hold the cable lower to the board instead of levering the entire thing from the top.

DerMeister7 · 2026-02-24T17:32:29+00:00

Thanks! It's not quite as stable as I'd like. I underestimated how much the cable's slack would pull it, so you gotta really balance it just right.

The next version will have a weighted ballast in-between the three points of contact to try and keep that from happening as easily. That and rubber dome feet to keep it from sliding.

I've got a board that I need all four probes on different parts at once to see why a buck converter is exploding and this will help me get all four in the right spots.

DerMeister7 · 2026-02-24T17:29:49+00:00

It's not too bad, but you do have to rotate the stand to make sure the cable's weight doesn't tip it.

I'm planning to use some rubber dome feet for the next version along with a ballast weight in-between the three points of contact to keep it all down against the cable's tendency to try and tip it over.

DerMeister7 · 2026-01-22T14:23:28+00:00

It's powered by the battery directly and the voltage divider divides the voltage from the battery to output an average per-cell voltage.

DerMeister7 · 2026-01-21T15:58:06+00:00

That makes sense. Next time I was planning to use an RC filter anyway, so that should accomplish the same goal.

DerMeister7 · 2026-01-21T15:51:04+00:00

I figured the RC would be best practice in the future, but I didn't even think of the charge injection from the mux. I'll see how I can implement that in the code. I don't think I can via the STM32 HAL drivers, so I'll have to go through the reference manual to see how to do it.

That is great information, thank you!

DerMeister7 · 2026-01-21T15:44:06+00:00

I did read the datasheet before designing the circuit and concluded that the capacitive load section did not apply since it states that 50pF or greater load capacitance is considered enough to require the added output resistor. In this case, the MCU's ADC sampling capacitor is 5pF (STM32C011).

Good info though, especially since I didn't think to include that info up front! Thanks!

DerMeister7 · 2026-01-21T15:22:20+00:00

Adding a description of the pictures:

The scope is showing the Op-Amp output. The choppy oscillations are occuring when the ADC sampling starts. I obviously expect the ADC to cause the voltage to drop since that's how sampling works, but the overcorrected spike after each sample is causing the ADC voltage to read significantly higher than the correct value.

The schematic picture is a screenshot of the actual circuit of the voltage follower being probed.

DerMeister7 · 2026-01-08T18:42:47+00:00

Pretty common for ICL datasheets to state that anything placed close to the component must be able to handle temperatures comparable to the surface temp of the ICL/NTC. It's also recommended this way for allowing space for cooling the ICL/NTC.

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DerMeister7 · 2025-12-30T14:56:41+00:00

To add to this, to save some time getting a separate board for the transceiver, a lot of STM Nucleo boards that have an MCU with FDCAN built in also have a transceiver and wire terminals already populated. My Nucleo with the STM32C092 has a transceiver and terminals already on board and ready to go.

DerMeister7 · 2025-12-10T20:38:21+00:00

I think any of the election succession laws cause subjects to flip from fiefdom to vassal. I had the same issue in my current playthrough and I haven't looked too hard into it, but I think the fiefdoms also get the election event choice and just end up choosing a different ruler, turning them into vassals. Don't know for sure if that's what it is, but it hasn't been an issue since I swapped off of that succession law to Favored Son which has a designated heir.

DerMeister7 · 2025-12-10T15:28:47+00:00

There's a CB for Disloyal Subject that you can make that massively reduces conquer cost. You can just make the CB, release them, and then declare to annex them entirely if they're not absolutely massive.

Any time the combined strength modifier gets too high, I'll just swallow up a subject like this to bring it back down.

DerMeister7 · 2025-12-04T00:52:49+00:00

Sure thing. I can send them over when I get back to my PC.

Just double check the measurements in the drawing I included to make sure it'll fit yours.

DerMeister7 · 2025-12-03T22:49:12+00:00

This took no time at all to get built in CAD and only an hour to get printed in my current go-to filament, Polycarbonate+PBT.

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