this post was submitted on 30 Jun 2025
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xkcd #3109: Dehumidifier

Title text:

It's important for devices to have internet connectivity so the manufacturer can patch remote exploits.

Transcript:

[A store salesman, Hairy, is showing Cueball a dehumidifier, with a "SALE" label on it. Several other unidentified devices, possibly other dehumidifier models, are shown in the store as well.]

Salesman: This dehumidifier model features built-in WiFi for remote updates.
Cueball: Great! That will be really useful if they discover a new kind of water.

Source: https://xkcd.com/3109/

explainxkcd for #3109

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[–] originalucifer@moist.catsweat.com 82 points 1 day ago (81 children)

welll........ devils advocate.. i could see the wifi being used so the device can be incorporated into the home automation system [climate control]. its not about dehumidifying, its solely about engaging the dehumidifying as needed.

[–] blackbelt352@lemmy.world 49 points 1 day ago (25 children)

Dehumidifiers already do that. They're equipped with hygrometers that kick the machine on or off depending on the relative humidity. It's old tech and it's pretty reliable, wifi isn't really necessary for it.

[–] AnyOldName3@lemmy.world 4 points 1 day ago (24 children)

The built-in hygrometer's not necessarily going to be as good as a well-designed home automation system, especially if the fan's not running all the time, so it has to wait for damp air to diffuse into the machine. It also lets you do other things, like not bother turning the dehumidifier on if there are open windows if you've got some way to detect that, or report the humidity to something that will graph it. It's not stuff that most consumers will care about, but a microcontroller with WiFi like the ESP8266 or ESP32-C3 costs less than an accurate hygrometer chip, so it doesn't make much, if any, difference to the final price, particularly if the product was going to use a microcontroller anyway.

[–] Cocodapuf@lemmy.world 3 points 1 day ago (2 children)

but a microcontroller with WiFi like the ESP8266 or ESP32-C3 costs less than an accurate hygrometer chip

Ok, two things.

First, the cost of the Wi-Fi chip is clearly not the issue here. The real expense/concern is the effort and software mechanisms needed to secure that network connection. Connecting to the Internet is easy, securing that connected device is hard.

Secondly, at some point you still need the hygrometer, there's no way around that. Either your dehumidifier is tracking humidity, or your home automation system needs to track humidity. And you can't like... get that data from the web somehow, you need a local sensor, and it will generally only make sense to have it in the same room as the dehumidifier (meaning not necessarily where other smart home components are set up).

[–] AnyOldName3@lemmy.world 3 points 1 day ago (1 children)

You're missing my point. It's likely that the cheapest way to design and build a dehumidifier these days will already include a microcontroller interpreting results from a digital hygrometer because these components are cheap and easier to work with than purely electronic/electromechanical designs with no microcontroller. The cost of switching from a non-WiFi/Bluetooth/Zigbee microcontroller to one with one or more of these networks is negligible, and once you've got it, it's not meaningfully more expensive to pay a software engineer to expose the on/off switch and hygrometer readings via that network and have the marketing people write Smart! Now with WiFi! than it is to skip it and pay the marketing people to come up with some other nonsense to put on the box. If you care about security as little as the average IoT vendor does, then it's nearly free to turn a dumb device into a smart one, so if it makes a handful of extra people buy the device, manufacturers will make things smart. For a dehumidifier, there are reasons why a handful of people will prefer a smart one, so smart dehumidifiers get made.

[–] Cocodapuf@lemmy.world 1 points 1 day ago (1 children)

It's likely that the cheapest way to design and build a dehumidifier these days will already include a microcontroller interpreting results from a digital hygrometer because these components are cheap and easier to work with than purely electronic/electromechanical designs with no microcontroller.

Well this part is definitely not true. A microcontroller and Wi-Fi chip are definitely more expensive than a wire, a variable resistor and a knob, which is all a purely electro-mechanical system would need in addition to the hydrometer.

The fancy digital version wouldn't be a lot more expensive, but it certainly wouldn't be the cheapest way to go.

That said, I think you're right that most companies will opt to go the fancy digital route to try to sell a "smart" product with more features. But then I expect there will also always be companies that manufacture simpler, cheaper products as well.

[–] AnyOldName3@lemmy.world 2 points 1 day ago (1 children)

The cheapest hygrometers these days only have a digital output, and a wire and a potentiometer aren't going to be able to query an i2c bus to ask the hygrometer what it's measured without the help of a microcontroller (and the microcontroller might be cheaper than the potentiometer anyway depending on the specific model of each - have you actually looked at the 2025 prices of things before making assertions about what they cost?). The analogue component of a hygrometer that actually does the measurement gives fairly small changes to the resistance/capacitance (depending on the kind of hygrometer), so the results need amplifying. If you're measuring on the same chip, you can get away with a simpler amplifier and digitally compensate for any nonlinearity, whereas to get a strong enough signal to make it to the rest of an analogue circuit without much degradation, you'd need an amplifier that ends up being more complicated than doing everything digitally.

[–] Cocodapuf@lemmy.world 1 points 23 hours ago (2 children)

Look, I'll be honest with you, I've never built a dehumidifier (I'm sure you're shocked). I don't know what exact components tend to be used. What I do know is that I have a fairly new dehumidifier and we have another one from probably the early 80s. Somehow they both work. Again, I'm not sure what components were used in the older model, but given the age I'd be very surprised if the electronics it uses would be more expensive to manufacture than the newer one.

Really, I think the idea I'm trying to get across is just that you can always aim lower. Sometimes the goal isn't achieving perfect precision, but rather achieving something good enough. Take toasters for example, most toasters don't have a timer at all. They have a little piece of metal almost touching a contact. When you turn the toaster on, that metal heats up and it bends until it touches that contact, ding toast is done. And when you turn the little dial from light to dark it just moves that piece of metal slightly further from the contact. My point is, it's not exact, it won't be the same on every toaster, and it will probably shift over time. It's a low tech solution for something that could absolutely be done in a more modern, more precise, and still inexpensive way (a simple timer). But it's cheaper and simpler to just do it the old way, and for many applications, that's fine.

Hell, I'm certain there are dehumidifiers on the market that don't have any kind of humidity sensor at all. Even simpler...

[–] bluGill@fedia.io 1 points 15 hours ago

If you don't have a sensor then that is cheaper in the short term, but it quickly wastes a lot of energy running when the humidity is under control. For a dehumidifier you need more energy to get lower so the room well generally will be fairly consistent not too low humidity even as outside humidity changes, but you will use a lot more energy than a system that turns off when humidity is good.

there are purely mechanical systems that used to be used. However they have some weird machining requirements so it isn't clear they are cheaper than a digital system (this partially depends on volume - make more and the machining gets cheaper per unit). The digital system is as we already have established is very cheap and lets you put buttons and LEDs on the unit for a few cents more - this is far more valuable to marketing than the possible savings (if any!) from a mechanical control.

[–] AnyOldName3@lemmy.world 1 points 16 hours ago

Again, I’m not sure what components were used in the older model, but given the age I’d be very surprised if the electronics it uses would be more expensive to manufacture than the newer one.

That's fundamentally where you're going wrong, then. 1980s electronics (for a dehumidifier, it wouldn't even be electronics, it'd be electromechanical) are often much more expensive than modern approaches, and even when they're cheaper, it's typically not by much. Over time, it's got cheaper and cheaper to precisely make small things, but the costs of materials haven't meaningfully gone down, so the 1980s approach costs about the same as it did back then, whereas digital electronics have plummeted in cost. Now, anything where the best approach was electromechanical rather than electronic is almost certainly cheaper to do digitally.

Take toasters for example, most toasters don’t have a timer at all. They have a little piece of metal almost touching a contact. When you turn the toaster on, that metal heats up and it bends until it touches that contact, ding toast is done.

Another great example of being out of date. Fifteen years ago, cheap toasters almost always used a bimetallic strip and the dial controlled the position of the contact it touched so it would have to bend more or less before it disconnected. In nearly every modern toaster, however, you'll either have something like a 555 timer and the dial will control a variable capacitor that changes the frequency of an oscillator to make it count slower or faster, or it'll have a dedicated toaster control chip like the BCT5512 and the dial will control a potentiometer that a capacitor drains through. Mouser list the PT8A2511PE toaster controller for £0.111 in bulk, but the cheapest bimetallic switch they carry (which is too basic for a toaster because it's got a fixed switching temperature) is the F13A17005L360100, which is £1.93 in bulk, more than seventeen times the price. (I suspect they used to have cheaper ones back when toasters still used them, and they've been discontinued now toaster manufacturers have stopped ordering them.)

But it’s cheaper and simpler to just do it the old way, and for many applications, that’s fine.

A lot of the time, the old way is more complicated and more expensive. Technology doesn't just let us do things we couldn't before, it also lets us do existing things in new, better ways, and being cheap is one of the most in-demand things. It's lower tech to hire ten labourers with shovels for a week to dig a hole, but it's much cheaper and faster to hire one labourer with a digger to dig it in an hour.

Hell, I’m certain there are dehumidifiers on the market that don’t have any kind of humidity sensor at all. Even simpler…

Having no sensor at all is certainly the cheapest way to do it, but we were talking about ones that do have a sensor, and whether, once you've opted to have a sensor, there's any major cost to making the device smart. If you're aiming so low-end that you don't even have a sensor, then you're clearly not concerned about the marketing benefit of extra features, so wouldn't bother making it smart.

So, first off, smart devices shouldn't need to connect to the internet, only the local network. I have everything connected to Home Assistant, and then for access outside the house I have HA connected to the internet, meaning I only have one point I need to secure.

On your second point, I think the poster above was talking about having both an in-built as well as wifi-accessible external sensor. It makes it possible to have a more powerful dehumidifier in one space, running to a lower humidity than needed based off what's going on in other rooms. Then have that air circulated by other fans, etc.

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