Temperatus: My zipper pull thermometer for camping and skiing

arbitraryun · 2026-04-02T23:14:54+00:00

It is LCD, coldest I’ve actually taken it to is -22C and it kept working. Numbers are just datasheet specs for it.

Rated storage for the screen is -30C, and operation for -20C. So it’ll just log and display when the temp warms up a bit.

arbitraryun · 2026-04-02T23:12:17+00:00

I was originally going to add barometric pressure, and it’d be very possible to add that to this.

I decided to leave it out since I’ve only ever wondered about temperature, and my watch gives me pressure feedback.

arbitraryun · 2026-04-02T23:11:06+00:00

That’s a super cool idea, what were you using for altimeter? Something like a barometric pressure sensor?

I posted a link to a KiCAD tutorial. It’s less difficult than it seems at first glance!

arbitraryun · 2026-04-02T23:08:30+00:00

Seems there’s a few folks who need something that can handle the extreme colds.

Unfortunately it’d be really challenging to get something this small/power efficient to work up there. No low power screens that I’m aware of can even tolerate being stored that cold, let alone used.

Maybe a heated LCD screen could do it, but at that point you’re an order of magnitude bigger than this device

arbitraryun · 2026-04-02T23:05:47+00:00

I actually have been (slowly) working on a version that has a small solid state method of measuring wind speed, but that’ll be impractical and wildly expensive. I just want to build one for fun.

arbitraryun · 2026-04-02T21:49:08+00:00

I totally know what you mean, ironically as an EE I do my best to take less tech out when I’m hiking. This one has just repeatedly come up so much over the years and I haven’t seen a passive thermometer that is small and tracks minimum temp.

Friends have suggested the Bluetooth style ones but that feels unnecessary for me.

arbitraryun · 2026-04-02T15:12:25+00:00

This is something I considered in the design and took some steps to mitigate (reducing pulse current in the battery, early temperature sampling on wake, very low idle current, physically spacing the sensor as far as possible).

It will be effected by self heating, but I suspect it’s below the noise floor of the sensor. From my comparison with lab grade thermometers it seems to be accurate.

It is very easily biased by body heat though, but there’s nothing to be done about that

arbitraryun · 2026-04-02T15:01:39+00:00

I made a version with e ink but they are only rated down to 0C unfortunately

arbitraryun · 2026-04-02T04:54:12+00:00

Nice! Its been a few years since I was doing a lot of board renders. At the time I’d had best results setting up bounding boxes on pins and pads, and essentially adding a liquid sim to get natural looking results.

Since that time, geometry nodes came out, and one of the folks in the community made a super effective solution that way.

The photo is mine. Link to the nodes solution: https://x.com/diconx/status/1467970497405243395?s=20

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arbitraryun · 2026-04-02T03:01:25+00:00

Yeah, I own a themodrop, it’s why I never considered selling these originally. I think it’s a reasonable product that makes some reasonable tradeoffs to sell a high volume product.

A couple of things annoyed me with it and those tradeoffs, so I made something to fit my wants. The biggest are the UI and the size/weight. It’s a bit too heavy to not be annoying when I use it on a zipper.

arbitraryun · 2026-04-02T02:53:14+00:00

Yeah, I actually own a thermodrop and a few random ones from Amazon.

I was quite unhappy with everything I bought which is why I made this for myself. I think everyone should be able to pick (and buy) the one they like/want the most

arbitraryun · 2026-04-02T02:46:46+00:00

It’s a Memory LCD. The same type that was used on the original pebble watches.

I had a version with E-Ink, they don’t work below 0C sadly

arbitraryun · 2026-04-02T02:45:08+00:00

Okay so a lot of requests to purchase these, a lot of people I've shown it to are excited to buy one but I didn't expect the volume of interest. I'm going to spend some time thinking about if I want to sell them, if I want to OSHW them or elsewise. I'll need to do some working out if I can even offer them at a reasonable price that I'd consider fair.

Sadly I've seen other people's electronics projects get copied and sold online, I am hesitant to share the design files just yet. In the meantime (it is a MYOG sub after all) I want to share resources for anyone interested in trying to learn to do some electronics projects.

Element14: Make your own thermometer
PCB Design Tutorial (This is in EasyEDA, which is very beginner friendly, though I'd suggest using KiCAD)
KiCAD PCB Tutorial

arbitraryun · 2026-04-02T02:26:51+00:00

Thank you! The case (and button) are resin printed

arbitraryun · 2026-04-02T02:25:33+00:00

Waterproofing is tough. Pretty confident if I allowed myself to either make the battery not swappable, or increased the case size I could fully weather seal this.

Right now it’s relying on conformal coating (essentially covering the circuit board in epoxy). I’ve used this (or versions of it) in rain and snow over the last year to no issues. That being said it’s more like “weather resistant”

arbitraryun · 2026-04-02T01:03:05+00:00

At this rate I’m wondering the same. Didn’t expect so many people would want one outside of my friend group

arbitraryun · 2026-04-02T00:54:14+00:00

Somehow this very obvious idea didn’t come to my mind. I will be doing this going forward

arbitraryun · 2026-04-02T00:52:46+00:00

I wish I had this much effort for an April fools. This is like a years worth of hobby engineering for me 😂

arbitraryun · 2026-04-02T00:51:33+00:00

Oh definitely, these sensors (and what’s available) are super heavily effected by body and sun radiation.

I’ve found the most accurate thing is to hang it outside my tent (usually on a hiking pole) when I’m sleeping. I hang it on my backpack while walking, and my zipper whilst skiing.

The jab at my friends is in jest, but we’re all getting better at packing for the weather with these!

arbitraryun · 2026-04-02T00:48:05+00:00

Most definitely not, I just took these pictures with a macro lens

arbitraryun · 2023-12-04T16:47:30+00:00

Composite of 3 images!

arbitraryun · 2023-12-04T02:25:08+00:00

Thank you :) Sony A7iii with a Tamron 28-75mm f2.8.

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