Wednesday, March 1, 2017

Floating bed, does it work?

I spent half years of my life in Brazil mostly kitesurfing and lying in hammocks. When I returned back to Finland I started to gather information about floating beds. I thought because hammocks were so much fun why not sleep the whole night in floating bed?

This is a floating bed from Bernstein Architecture. The bed can be made motionless with tightening the cables.

This is a floating bed made from a trampoline.

Creating a floating bed is simple. Just hang cables from ceiling and attach to the bed. But because I didn't know how a floating bed would feel and what are the best places to put the cables, I decided to make a prototype first. Then I would not need to ruin my bed and ceiling in experimenting the proper installation.

The cables can be installed in three ways.

This way the bed behaves like a hammock and tilts when pushed.

This also tilts when pushed but it tilts the other way and you feel like you are falling off. If pushed enough you might really fall off.

When the cables are installed this way the bed stays level all the time. This is what I chose for my prototype.

At first I created two structures with two 2x4's to put my bed on.

 I tried first with only one 2x4 but it started to bend. This way it would only bend a couple of millimeters.

I created same kind of structures near the ceiling. These structures are not attached to the ceiling in any way. The structures are both 2,95m wide and there wasn't too much bending even with two peoples weight. The structures are only attached to walls and the actual load is on only one 2x4's at each corner.

Here's how simple the structure is.

Ok, how did it work? Not good. I really tried to like it and tested for a couple of weeks just to be sure. I really wanted this to work. But I could not sleep properly. Because the ropes don't have much friction, the bed starts swinging from even the slightest movement and the it takes a long time for the swinging to stop. So every night I went to bed, it took a long time before the bed would be still.

I don't get easily sea sick, I for instance kite surf. But imagine sleeping in a bed where every time you inhale and exhale, the bed moves with you. Not much but you feel it's moving. Every time you move during your sleep, the bed moves also. I tried this bed for a couple of weeks but I just could not get proper night's sleeps with it. I started having sleep debt.

So if the bed behaves like this with only one people, you understand it does not work with two...

It was still wonderful to wake up in it in the mornings. It felt like I was floating in a raft in a calm sea. So there were some positive sides but when the negative side was poor night's sleep, I had no other choice than to decide not to use it anymore.

The material cost was around 100e so it was very cheap to test. I've also decided to use the materials for a hanging sofa for the terrace. Like hammock, you mostly use it for quick naps so it doesn't give you sleep debt for weeks. 

If you still want to buy a floating bed, maybe you should also first build a prototype like I did so you can be sure it is really right for you.

Sunday, February 26, 2017

What are corner mirrors and how they work?

Corner mirrors are two mirrors places in 90 degree angle usually in the corner of the room. Because they are in 90 degree angle the image is reflected through both mirrors and therefore reversed twice.

I've had corner mirrors in my apartments since I was studying in Oulu university. The first ones were made from small 30x30 mirrors. Now for the first time I have a full-size corner mirror. It's still a "prototype" meaning it's not properly installed.

The left side reflection is the "normal" one-mirror reflection and the right side reflection is the two-mirror twice-reversed reflection.

Because the corner reflection is reversed twice it shows my reflection as others see me. So here I'm waving my left hand and the corner reflection also waves his left hand.

The corner mirror's reflection also always stays in the same place, in the corner. When you walk around the room, the reflection "follows" you like Mona Lisa. Always facing you and staying in the same place. No matter where you are in the room, you can always see your reflection in the corner.

Because the light always goes back to it's origin in corner mirror, it's also used in measuring the distance of the moon. The laser beam is emitted from earth to moon and targeted to corner mirror placed there by the astronauts. Because the corner mirror always reflects the beam back to it's origin, moon's distance is measured from delay of the beam getting back to earth.

Lunar Laser Ranging experiment
Corner reflector

Here's the whole video about how corner mirror works:

Monday, February 13, 2017

Trying to find correlation between swimming pool heat loss and outside temperatures.

My swimming pool pump is now being controlled with my home automation and it keeps the water temperature between 20,5-21C. It only pumps during day time 09-23. Because it's only controlled by water temperature, the colder it gets, the more pump is used. So examining how many hours the pump is used daily, I can roughly estimate how much the pool uses heating energy.

So I collected the daily pump usage.

This is the raw data. There are some spikes and dips which have to be removed first.The baseline seems to be around 4 hours. The dips happen when I forget to tell home automation I've finished swimming. After that there is always a spike because the pump has to do a 'double-shift' to get the temperatures back to normal.  There is also a couple of days with 14 hours of pumping and that was because I didn't use pool cover in those days. It's winter so air is dry and lot of pool's heat will go away by evaporation if the pool cover is not used. My heat exchanger is also old and I have no idea how efficient it is now and how efficient it should be.

I also changed the target temperature from 21C to 22C in 27.1 so the last spikes come when the pool temperature is rising.

At first I removed all the spikes and dips manually.

Looks a lot better but there's still a lot of variation between days.

My home automation also records hourly temperatures from Finnish Meteorological Institute so I took an average for daily temperatures and added those to chart. I reversed axis for temperatures so it's easier to compare with pump times.

There's a slight correlation but not much. The pump hours start to rise after 1.1. Of course the last week is different because the water temperature is now 22C. Actually the reason why I started to examine these temperatures was to find out how much more heating energy is needed after I raised the water temperatures. But there are too many variables in this equation.

This graph shows correlation between air temperatures and pump hours. The correlation is weak, R2 is 0,24 but there is at least some correlation.

But from temperature graph can be seen that pump hours start to rise even when the temperatures stay the same. I think the problem is I don't measure the ground temperatures. The pool has two ways to loose heat, into to the air by evaporation and into the ground by conduction. The pool has cover so only heat is lost into the ground.

As I said, I don't (yet) have any thermometers measuring ground temperatures but I found a graph that shows how ground temperatures change in Finland yearly ( actually in Estonia but it's almost the same in southern parts of Finland ) .

This graph shows the ground temperatures are the lowest in February which makes sense because there's a lot of mass that has to be frozen/heated. Same applies in summer, June is not the warmest month but July and August.

What I was trying to do was to find function that gives me pretty good estimation of what heat loss will be if the function is given enough information. It seems the function needs the ground temperatures more than air temperatures. If I can create a function that estimates the heat loss, I can also create alarms if there's something wrong in pump. I already have same kind of estimation for my computers water cooling. The function uses CPU usage percentage and estimates what the CPU temperatures should be.

The green line is CPU%, red is estimated temp(scaled), brown is actual temp and blue line actual temp divided by estimated temp(scaled). If blue line is something other than around 60, then there's something wrong with water cooling. As you can see, it's fairly flat even when CPU usage and temperature changes.

If I can create as good estimation function for the pool, I can also accurately compare when I change something in my pool system like start using higher water temperatures. It seems a proper way to do this is set additional thermometers into the ground but that has to wait till the summer.

Thursday, December 1, 2016

Hieman erilainen joulutähti, Orion

Monta vuotta sitten tein pirunnyrkin nimeltä Orion. Pirunnyrkin viimeistely jäi silloin tekemättä, mistä johtuen sen kokoaminen vaati hieman väkivaltaa ts. siitä tuli vain sisustusesine. Nyt otin iltapuhteeksi hioa Orion hieman väljemmäksi ja käytettäväksi.

Orion koostuu 24 palasesta, joista puolet ovat toistensa peilikuvia eli erilaisia palasia on vain kaksi.

Joistain osista on lähtenyt palasia irti johtuen tuosta liiasta tiukkuudesta. Osat sahasin tavallisella sähköpistosahalla, mutta alustana oli itse rakentamani, jolla oli helppo tehdä eri asteisia kulmia.

Kokoaminen lähtee tekemällä palasista ristejä. Helppoa!?

Sitten vaaditaankin hieman sitä taitoa tai taikuutta :)

Kuvaa katsomalla kyllä selviää miten nyrkki muodostuu mutta mitenkään helppo se ei ole koota. Tulitikkuaski vieressä osoittaa ettei kyseessä ole mikään pieni pirunnyrkki :)

Thursday, November 17, 2016

Paljonko blogien mainonta tuottaa?

Selvittelin n. vuosi sitten kuinka kannattavaa blogimainonta oikeasti on. Tietoa ei ollut helppo saada, koska kukaan ei sitään suoraan sanonut. Ihmettelin lähinnä sitä miten kukaan voi tehdä päätöksiä bloggaajaksi ryhtymisestä, jos ei ole tiedossa miten ansaintamalli toimii.

Oma bloginihan ei mainoksia sisällä. Kävijämäärät ovat sen verran pieniä eikä tätä ole tarkoitettukaan massoja keräämään. Täytän vain internetin aukkoja eli tietoa mitä täältä puuttuu ja mitä itse olisin tarvinnut kun jotain asiaa selvittelen.

Tarkennan vielä että tässä puhun nyt perus-klikkimainonnasta kuten Googlen Adsense. Paremmille tuloille voi päästä jos kohdentaa mainontaa suoraan mainostajien kanssa tai sitten esimerkiksi tekemällä "puoluettomia" postauksia ilmaiseksi saaduista tuotteista. Mutta nämä kaksi eivät siis ole niitä mitä nyt käsittelen tässä tekstissä. 

Olen jo pitemmän aikaa aikonut kirjoittaa blogimainonnasta ja nyt kun viimein sain tämän työn alle, niin huomaan että kenttä on muuttunut jonkun verran. Kun pistät hakukoneeseen "bloggaajan tulot", tulee hakutuloksena sata blogia missä käsitellään miten blogista saisi rahaa. Olennaista kaikilla tuntuu olevan että se oikea tieto puuttuu ja blogissa on mainoksia ts. tuottavat kirjoittajalleen rahaa olemattomalla tiedolla. Toimiva täky siis.

Toinen mikä on muuttunut on poistuminen millä aiemmin pystyi hyvin seuraamaan eri sivustojen kävijämääriä. TNS listaa lähinnä vain suuria lehtiä kun taas keräsi myös yksittäisiä blogeja ja datana käytettiin Google Analyticsin dataa. onneksi löytyy kuitenkin Internet Archivesta ja sieltä voi keräillä tietoja ennen viime kesää. Esimerkiksi:

Aiempiin laskuihini käytin blogien tuottotietoina lehtien artikkeleita, joihin tietenkin pitää suhtautua vähän varauksella koska ne ovat bloggaajien itsensä ilmoittamia. Toisaalta kun useamman blogin tiedot sain kerättyä, summat kuitenkin olivat lähellä toisiaan.

Tavoistani poiketen en voi kuitenkaan tässä esittää alkuperäisiä lukuja kun minulla ei ole niitä enää saatavilla. Ne olivat tallentamattomassa LibreOffice-kaaviossa joka on siirtynyt jo boottausten myötä ajasta ikuisuuteen. Mutta sain niistä selkeän muistisäännön millä voin arvioida esimerkiksi onko Youtubeen uuden videon tuottanut saanut videon tuottamiseen kuluneet rahansa takaisin. Jotta saisin yhden euron, tarvitsen n. 400 klikkausta. Hajontaa oli noissa 300-500 välillä mutta 400 vaikutti olevan hyvä keskiarvo. Youtube-videoita katsoessa päässälaskemisen helpottamiseksi käytän 1e/500katsojaa muistisääntöä.

Nyt se on tehty. Internetin suurin salaisuus on paljastettu.

Ai miksi kissa?
Klik Klik!

Keräsin taulukkoon hieman blogien sivunlatausmääriä ja arvioituja tuottoja.

Saturday, November 12, 2016

Water loss of swimming pool with and without pool cover

In my earlier post Heat loss of swimming pool with and without pool cover I tried to estimate the heat loss. In this post I test how much water is actually lost in evaporation.

I used Bosch PLR 50 C Digital Laser Measure for measuring the water level. Because the laser cannot actually measure the water level, I used a floating plastic box with some weights to reflect the laser light. It's got Bluetooth interface so you can save the measurements on Android app but I didn't need the feature in this.

Without the pool cover the pool looses water about 1mm/day. I wanted to test with pool cover because I needed to be sure that there isn't any leaks. It's an indoor pool, with ceiling fan constantly blowing out moisture with minimum power.

Without pool cover I tested for 17 days, and the evaporation was quite constant.

In average the pool lost 1,2mm daily and with 2,8x5,7 sized pool that meant loosing 19,5 liters of water daily.

With pool cover I tested for 10 days and the pool only lost 1mm in that time 1mm being to measuring accuracy and minimum change that could be measured. That meant that with pool cover it lost only 1,6 liters daily and about 1/10 of without pool cover. 

The average daily water usage per person in Finland is 155 liters so additional 20 liters is not so much compared to that especially if it's been divided between more people. The bigger problem is the high humidity level in pool room which means in winter that moisture can condensate inside the walls.