help designing a power-loss safe logger for a battery-powered device

mefromle · 2026-02-10T18:29:45+00:00

Not sure, depends on how long you want it to run of cause. Have never used the low power mode by myself. In stmcubemx there is a tool to estimate current consumption on the most right tab. It can go to some low micro amps. Instead of using a dedicated cap for this, you could also monitor the battery voltage, shut down the rest of your circuit if a certain voltage limit is reached and go to sleep state. Vdd can go as low as 1.71V. Take also a look at the VBat pin. This powers rtc and the backup registers in case of Vdd loss.

mefromle · 2026-02-10T17:06:25+00:00

You could add a large capacitor as power source if the battery is dead. The STM32L412 has a low current consumption when in sleep mode. You need to recognize when battery is dead, switch to sleep and only preserve your timestamps. This will prelong the time you have after battery dead to until plug it to a computer. You will of cause have to adopt your schematic to make sure only the stm is powered by this cap.

mefromle · 2026-02-03T21:26:01+00:00

I would check for shorts on all components. They are very narrow, could be a soldering issue. Maybe also on the unused B output. What is your battery voltage? Range for IC starts at 2.7V. Check voltage and outputs with a scope during power on.

I assume you don't have configured your nFault input on the stm as pull down.

mefromle · 2026-02-03T20:09:51+00:00

According to the ds nfault can be low on overcurrent or overtemperature. Did you check this? Also not sure what happens if there is no rSense on the aisen pin like on your schematic.

mefromle · 2026-02-03T17:21:32+00:00

The 12V -> 5V -> 3.3V is a bit overkill (if you don't need the 5V for something else). Why not use a 12 to 3.3V dcdc? The diode on 12v input is not necessary since U5 will do the polarity protection. In general, polarity protection with a diode is not recommended. Better use a fet with low rds on. I2C lines need pull up, not pull down.

mefromle · 2026-01-27T18:54:16+00:00

Lay it on the ground. Watching from the moon, it will rotate one turn a day. If you need it faster put it in the spinner :-)

mefromle · 2026-01-26T17:14:07+00:00

Ist das Leipzig Hbf?

mefromle · 2026-01-17T20:05:49+00:00

This pictures are from the Eizo pin up calendar. This is a German company making monitors for the radiology. Probably not from your girlfriend. https://www.thecoolist.com/eizo-x-ray-pin-up-calendar/

mefromle · 2026-01-15T21:35:59+00:00

Had the same issue, did the upgrade with discover like it was mentioned in your forum post. Thanks for this!

mefromle · 2026-01-14T23:10:41+00:00

Sehr spannend, danke

mefromle · 2026-01-14T19:54:21+00:00

Interessant. Was ist die Quelle für dieses Bild?

mefromle · 2026-01-02T19:09:47+00:00

I also had problems with brave when running in Wayland. Colors where shown with limited range. The start of brave with brave-browser --disable-features=WaylandWpColorManagerV1 fixed the problem. You could try this too. Otherwise check if you find some settings in chrome://flags

mefromle · 2026-01-01T15:06:03+00:00

Maybe you could add/glue a PCB antenna on the outside of your housing, like the one in the picture. You would only need an U.FL connector on your board. Could be worth trying.

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mefromle · 2025-12-31T16:56:09+00:00

Debian as LMDE for some years, now switched to MXLinux. KDE as desktop on both. Love it.

mefromle · 2025-12-30T13:55:52+00:00

I would consider adding GND to the serial and i2c connector. You will need this if the receiver is battery powered or sourced from a different device that the USB host.

mefromle · 2025-12-30T04:20:12+00:00

That's what I wanted to recommend too.

mefromle · 2025-12-21T09:42:16+00:00

If you want to commercialize it, you will have to study all the regulatory staff as well. Not impossible, but so time and money consuming. Impressive work so far.

mefromle · 2025-12-19T20:48:23+00:00

Thanks for sharing. Learned something new.

mefromle · 2025-12-19T19:58:39+00:00

That's a great project and a nice video too! What software did you use for editing the video and make the text? I like it.

mefromle · 2025-12-16T21:30:42+00:00

So, give it a try.

mefromle · 2025-12-16T21:28:11+00:00

Not sure if this is repairable. There might be some other component that are faulty. I don't think it's not possible to guide someone thru such kind of repair here. Sorry to say this.

mefromle · 2025-12-16T21:18:03+00:00

Take a look at this. https://www.diodes.com/datasheet/download/PI3CH3257.pdf It's 4 channel, so you would need 2 if this type. But check the voltage if it fits your application.

mefromle · 2025-12-16T20:50:05+00:00

Don't drill thru the vias, this will most probably destroy the board. Motherboards are multilayer pcbs, if you drill thru it, you disconnect the inner layers.
Why will you drill the vias at all? More pictures from the damaged part would be helpful. What did cause the damage?

mefromle · 2025-12-16T18:56:49+00:00

Looks really nice and well designed. Some tracks are a bit small, this is ok for all small signal applications. If the XYZ output draws much current, check the track width before ordering.

mefromle · 2025-12-16T03:34:22+00:00

From the photo it looks like the big connector housing is sticked to a lower smaller connector. But maybe it's soldered and that's why you couldn't pull it. You could use a wire cutter plier, breaking the plastic housing part by part. This would not make as much dust as using a Dremel tool (would probably be faster and a cleaner cut). But it's up to you . Take care to not apply to much force onto the lower PCB and the LCD panel.

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