• 3 Posts
  • 507 Comments
Joined 2 years ago
cake
Cake day: June 12th, 2023

help-circle
  • That’s not how AC works at all.

    AC works by evaporating a gas, evaporation (going from liquid to gas) takes a lot of energy. By dong this inside a ribbed evaporator, the energy gets extracted from the evaporator cooling it down. Then a fan ventilates the air in the room over the evaporator, which in turn extracts the energy from the air. On the other side the AC has a compressor which turns the gas into a liquid. This takes energy to do, so the compressor puts all that energy in, heating up in turn. A large condenser (looks like a radiator) is used to cool the coolant down. The compressor puts in energy in the form of pressure, but as the gas is hot it can’t turn into a liquid. By cooling it down in the condensor it can turn into a liquid. A fan is used over the condensor to dump the energy from the gas into the outside air.

    For gas in the past something like R134a was used, these days something like R290 (propane, but very pure/clean) is used which is better for the environment. In a very real sense ACs are energy pumps, they take the energy from inside and dump it outside. But they can also work the other way around, taking energy from outside and dumping it inside. This leads to pretty cool effects where you can heat your home with more than 100% efficiency. Because the energy you need to put in is only the overhead for pumping the energy, but the amount of energy being pumped can by much much larger. Over 100% efficiency in a closed system isn’t possible, but since an AC dumps the energy in the outside air it isn’t a closed system. ACs are also known as heatpumps for this reason.

    The way an AC can be used to dehumidify is because of the dew point in the air. This is a combination of the amount of moisture in the air, the pressure and the temperature. When the AC pushes the temperature from above the dew point to below, the air can’t contain all the moisture it contains. This will cause the water to condens on the evaporator in the AC. This can (and probably will unless you are in a very dry area) occur during normal cooling operation. This is why there are normally lines to take the water and get it out of the AC unit. When the water would remain, it’s a breading ground for all sorts of nasty stuff (look up legionnaires disease), so it’s important to get it out of there. A lot of times a small water pump is used to pump the water away.

    When cooling the AC tries to regulate the amount of energy pumped to keep a constant temperature in the room. Older/cheaper ACs just do this by start/stop, but better more modern ACs can regulate their power to prevent big swings in temperature and save energy. But when in dehumidify mode, the only purpose is to push the condensor below the dew point. Now the AC could do all sorts of fancy calculations to figure out the dew point and get it there. However that isn’t done at all, most ACs just push the temperature down as hard as they can. This is because the further you get down below the dew point, the more water condenses, so it gets the moisture out faster. And it’s also really complicated to calculate the exact dew point and get the measurements, because the AC itself influences the measurements a lot, so it would need sensors further away. Some big systems can do this and also measure the amount of moisture in the air and regulate to that. But small systems people have at home usually just go as hard as possible.

    This is the reason why it just never stops in dehumidify mode and the air gets colder and colder. Nerds can probably get something cooking with sensors and homeassistant, but regular home systems won’t go to a target when in dehumidify mode. There are hard limits to how cold it will allow the condensor to get, to protect the system and prevent frost, but that’s not really the same as a target temperature in cooling mode.

    Some better ACs also have a smart dehumidify mode, where it closes the inside unit, turns off the fan. Then cools down the condensor a huge amount. Then opens the inside unit and slowly blows air. This way it can get a lot of moisture out of the air fast and not cool down the air a lot at once. But in the end it’s the same effect. The energy still comes from the room, so the room will cool down, it will just not have huge swings in temperature.



  • My personal advice: Take notes.

    Just write everything down. I recommend an actual physical little paper notebook and a pencil. If you think: “Oh I must remember that” or “I’m almost out of …, I must buy more”, write it down.

    Now don’t go writing down stuff like fun facts or YouTube videos you want to watch. Make it all practical stuff, stuff you need to do or is important in your life. It’s your brothers birthday next week, write down the date and what you need to do to prepare. Your stomach hurt and you think you ate something that didn’t agree with you, keep a log of what you ate and how your stomach felt. That way you can identify allergies or things you can’t eat (anymore). Having trouble remembering names? Write down after you met someone: “Today I met Steve, Steve is in charge of accounting at Megacorp.” Measured the room you want to put new flooring in? Make a little sketch and put the measurements in.

    Writing stuff down physically forces your mind to pay attention and remember it later in a structured way. It also feels really good to physically tick off a task or cross it off. It can be a bit hard to keep up with and not go the other way and put so much into it, it doesn’t help anymore. But it can help a lot, especially if you are the kind of person that thinks 8 times a day to put out the garbage, only to wake up the next morning and you’ve forgotten to actually do the thing.




  • You are right in how wasteful it is, especially since it turned out a lot of those satellites don’t even make it to 4 years.

    However there is zero risk of space trash with Starlink. They orbit so low, it’s basically within the atmosphere still. They need to constantly boost themselves, otherwise they fall down and burn up. So these satellites are coming down within years all on their own, even without any controlled disposal.

    It’s insanely wasteful, but it keeps SpaceX in business launching every week, which is kind of the point. But at least there isn’t a Kessler syndrome waiting to happen.








  • I remember when I was 15 living at my father at the time and my girlfriend was visiting for the weekend. I had to work on Saturday, but she wanted to stay over the entire weekend and would find something to do whilst I was gone. I told her to be free to use my computer.

    We also had a couple of cats and one of them would always hang out in my room. Now this wasn’t your regular cat, this was a big boy. Not fat, just a huge bundle of muscles, big claws and huge teeth. We’re talking dog sized cat here. He was very sweet, but could be a bit playful and use his claws and teeth whilst playing. He was very careful with humans and tried to be gentle, but it could be intimidating for people who didn’t know him.

    When I got home I found the cat sleeping on my desk and my girlfriend on my bed reading a book. I asked her how her day went, she pointed to the cat and said: “I wanted to use the computer, but that asshole over there didn’t let me.” Apparently what happened was the cat lay down in front of the keyboard, easily blocking the whole thing. And every time she wanted to type he would try to grab her hand and play with her. Being so large, she got scared of him and just didn’t use the computer. The cat declared victory and slept in front of the keyboard to celebrate, thus blocking the computer all day.

    After she got to know him better, they got along just fine. He was such a sweet boy and never hurt anyone on purpose. You did need to be careful giving hem treats tho, T-Rex chomping off a hand comes to mind with that one.




  • Yup, that’s the one.

    I think where I live it’s a company that offers the whole thing white label to supermarket and other shops. The systems are very similar across a bunch of different stores, but the branding is specific to the store. So their logo, their colors. Not just on all the UIs (both the scanner and the checkout), but also the physical hardware colors.

    The hand scanners all run Android, the other day I got one that said Google Play Services had crashed. The scanner itself is probably made by Zebra and then customized by the company providing the scan and checkout solution.

    It has become super common around here, to the point where I’m annoyed when it isn’t an option and I have to use the self-checkout where you need to scan at the checkout.


  • No, the hand scanners aren’t connected to the kiosks. They are at the entrance, you pick them up, scan all you want to buy. Then at checkout you place the scanner into a kiosk, it knows what you bought and you can checkout as usual. Every once in a while a store employee takes the scanners and puts them into the holders in the entrance. Depending on the size of the store there can be up to a hundred of these scanners available.

    Other stores do the same, except your phone is the scanner with an app you can download. It works basically the same way. Most stores that offer the app also offer the hand scanners, which I prefer.


  • For me personally, the self checkout is just a way better solution to the problem. It’s for me much faster and more efficient. It’s also easier for the store itself. The best kind of self checkout for me is where you can scan everything with a hand scanner or app whilst shopping. Then just pay at the self checkout and walk out. That way I just put the stuff in my bag directly, instead of from the shelf into the basket or cart. Then from the cart to the checkout and then from the checkout into my bag. It also spreads out the action of scanning the products, which means avoiding a slow and repetitive task scanning it all in 1 go. I’m also not blocking a checkout whilst scanning. I hate it when stores that offer the hand scanner have people scanning a whole cart full of stuff at the checkout. And then bagging it of course, which blocks a checkout for ages. Just go to the regular checkout if you want to do that, the cashier is faster than you are and you can focus on bagging exclusively.

    However the lack of human contact is an issue. I’ve seen a lot of stores that offer self checkout recently make one or two lines available for chatting. It’s just the regular oldskool cashier, but they are relaxed about it and chat with the customer. This means people in a hurry or that don’t need contact right then can go fast through the self checkout. And people who like to chat can use the chatty checkout with a good old human being.

    This for me is the best way to apply new tech, all of the benefits for all parties involved and hopefully none of the downsides.


  • In trouble shooting it always important to answer at least these questions when asking for help:

    • What are you trying to achieve, eg what is the end result you are hoping for.
    • What is the expected behavior, or how do you think it should work?
    • What is the experience behavior, so what actually happens and how does that differ from what you expected.
    • What steps have you taken in trouble shooting. Are there things you’ve checked or ruled out? How so? What did you try?
    • Any background you think is relevant, so which software, hardware, versions, urls etc.

    This will help other people help you quickly and efficiently. This will greatly improve your chance of other people being able to help you, or you being able to help yourself.


  • Are you referring to the red ring of death on the Xbox? Because that has absolutely nothing to do with ATI. They just made the chips, it’s Microsoft that put them on the board. Most of the issues were caused by a poor connection between the chip and the board, not a hell of a lot ATI could do about that.

    A lot of it was engineers underestimating the effect of thermals between 80 and 95 degrees for very long times, with cool down cycles in between. The thinking was this was just fine and wouldn’t be an issue. It turned out it was an issue, so they learnt from that and later generations didn’t really have that issue.