I designed my new central heating system in the most flexible way: it basically has heat generators, heat consumers, and a heat store. It has a hot water cylinder, used as the store; the generators are 6 solar panels (thermal, not photovoltaic), and a wood-based water boiler (the livingroom fireplace); the consumers are the hidraulic radiant floor (used to warm-up the house), the domestic tap hot water, and the swimming pool.

My new system as just been installed (a Rigsun Stratus cylinder with Alpin panels) and is working very well (a big thankyou to the HotSeason guys! ); now I want to keep a record of all the relevant system’s temperatures. The solar controller has acess to many, but I also need to know the radiant floor intake and return temperatures. For that, the fitters installed a couple of sheaths to receive Rigsun (actually, Resol) PT1000 probes.

I’m using an Arduino to bridge the software to the PT1000 probes, so now I only needed to study the details of the sensor reading circuit. The PT1000 changes it’s resistance with temperature, more specifically 3.85Ω per degree Celcius. I’m looking for the simplest solution that fully satisfies my needs (read: cheapest possible). A simple voltage divider circuit will give me a voltage value the ATMega can read. The PT1000 ranges from 1000Ω to 1385Ω from 0-100˚C, wich translates to a small voltage range. A simple study showed me which was the best candidate for a company fixed resistor that gives the bigger voltage swing:

I simply plotted the voltage divider equation. The red curve is the output voltage, the blue curve is the voltage swing in function of the companion resistor value. In the best case resistor (about 1150Ω, that’s the highest point in the blue curve) we have a 0.4V swing, but values in the 2.5V area. In the simplest cases, the ATMega reads values from 0-5V or 0-1.1V (internal reference). With the 5V reference, that’s a 1.2˚C resolution, not great.

I tried to change the resistor to lower the working voltage (to be within the 1.1V reference); that gave me a 5500Ω resistor, 0.23V swing, and a final resolution of 0.45˚C. Much better. Obviously, a better approach was to use an opamp to amplify the signal, or buy an off-the-shelf PT1000 4-20mA converter. But remember, I’m looking for the simplest/cheapest solution. Half a degree Celcius of resolution is good enough for what I have in mind.

I know I said this worklog would be in portuguese but hey, this post was already written by then… sometimes the Internet time flows in wierd patterns…

Estou de volta ao meu blog, após um óptimo e merecido período de férias! Tenho tido muito trabalho (no emprego e fora dele), o que me impediu de escrever, mas agora vou tentar manter o ritmo.

Para isso, vou começar um worklog do meu projecto ultra-secreto! Vou fazê-lo em português (pelo menos para já), e por uma razão muito simples: as pessoas que me podem dar algum feedback e ajuda preferem a língua de Camões…

Bora lá!

Vá lá malta, digam-me o que acharam da disciplina, se srviu para alguma coisa, se foi uma seca, etc.

Fico à espera dos vossos comentários (que, claro, são obrigatórios)!

Divirtam-se!

Não, não estou a falar de uma bonita e atraente rapariga mirandesa… que aposto que as há!

Falo de carne mirandesa, biológica, 100% certificada. Comprámos ontem (no Jumbo em Aveiro), hoje foi parte do nosso alomço, e ficámos ma-ra-vi-lha-dos!

Simplesmente grelhada na brasa, 2 minutos de cada lado e hop! Já está! Estava mesmo au point, levemente rosada. Acompanha um arrozinho branco e courgetes laminadas, salteadas com alho. Uma delícia!

O vinho era um Encosta da Estrela, um vinho muito agradável e fora do comum, mas talvez um pouco “forte” para mim. No entanto acompanhou divinalmente esta refeição!

Experimentem!

I’m studying the hardware and software for my Home Automation project, namely for the server and clients of the SCADA system. I won’t use Windows for these systems, because I need something that I can trust (and immune to viruses/trojans/attacks), and in the end it gets expensive. MacOS X and Linux comply (better at least) with that, and it’s relatively easy to find good, cheaper systems they run on.

But I’m studying how I can include Amiga-based systems on my project. The reasons for choosing an alternative system are simple:

* Lower power consumption, good for the environment.
* Supports smaller, innovative companies, good for the economy.
* Really small, efficient and fast operating systems.
* Secure (different from mainstream OSs, unexploited).
* Virus immune.
* Usually cheaper than a Windows system (the OS is payed separately, and usually needs better, more expensive hardware to perform well).

I won’t deny that the Amiga had a big impact on my life, during my childhood… a lot of what I know now was learned on an Amiga, and the Amiga community surely influenced many of my (good) choices in life. Including it’s spirit in my project can only bring good things!

As of now, my options boil down to this:

AmigaOS 4
Expensive system (~700€).
Dedicated hardware (ACube’s SAM440ep motherboard).
Hardware available commercially today.
Good performance.
Low power consumption.
Good operating system support of the hardware.
No JAVA.
Has SDL.
Good future perspective.
Developer: Hyperion.

MorphOS
Reasonable system cost (~300€).
Dedicated hardware (Genesi stuff), with support for some obsolete PowerPC G4 Macs (MacMini).
Hardware not really available, as of now only runs on obsolete systems (Efika/Pegasos/Radeon). Will certainly support the new Genesi Smarttop and Smartbook.
Good performance.
Low power consumption.
Good operating system support of the hardware (on the Efika/Pegasos at least).
No JAVA.
Has SDL.
Good future perspective.
Developer: the MorphOS team.

AROS (Icaros Desktop)
Cheaper system (iMica: ~250€).
Generic hardware.
Hardware available, but limited operating system support of the hardware (targets old x86 hardware), although the iMica is available, and can be used to give value to old computers with lower power consumption.
Good performance.
Low power consumption.
No JAVA.
Has SDL.
Uncertain future perspective, since it is developed by the community, with no commercial company backup (although this sometimes means nothing).
Developer: AROS community.

MacOS X
Normal system cost (MacMini Intel: ~500€).
Dedicated hardware (Apple stuff).
Hardware available commercially today.
Best performance.
Low power consumption (30W).
Good operating system support of the hardware.
Has JAVA.
Has SDL.
Good future perspective.
Developer: Apple.

Linux (DSL, Ubuntu, PuppyLinux, …)
Cheaper system (~300€).
Generic hardware.
Hardware available commercially today, and can also be used to give value to old hardware.
Good/Best performance.
Low power consumption (40W).
Good operating system support of the hardware.
Has JAVA.
Has SDL.
Good future perspective.
Developer: the Linux community.

Preliminary observations
It’s not easy to choose the OS by reading these facts. I took a look at AROS, but I’m yet to see AmigaOS 4.1 or MorphOS running, and using the OS is an important part for me. Also, I have to make a bit of development on the three and see wich one feels better.

My emotional side tells me AmigaOS might be the way to go, but it seems to cost more than a Mac or Linux system. From this simple comparison AROS is the best value and MorphOS (assuming it will run on the MX Open Client “Smarttop” from Genesi) is as strong a candidate… I’m eager to try them out, and I’m sure testing sessions will be lots of fun!

I’m into some retrogaming lately, mainly on the Amiga. This made me look at the Amiga scene, and I’m really happy about the recent events.

Another one of these is that apparentely, Hyperion is going to push Java onto AmigaOS 4.2! Even if not a complete/modern version, having a Java VM on AmigaOS is (IMHO) mandatory.

Things are looking good for this (seemingly?) dead platform!

Vou só deixar aqui uma nota de relevo para uma party que vai acontecer em França, nos dias 6, 7 e 8 de Novembro, e que me parece ser muito interessante (principalmente para antigos Amigans como eu). Chama-se Alchimie 2009.

O tema recorrente é, claro, os sistemas alternativos (Amiga, Ubuntu/Linux, Haiku, …). Este ano, os temas são a robótica e a computação ecológica (baixo consumo e eficiência). Parece ser tudo malta muito fixe e criativa, dentro do antigo espírito saudável do Amiga, e os assuntos abordados são também eles muito interessantes!

Tenho imensa pena de não poder ir (simplesmente não dá)… mas vou colocar a data na minha agenda e para a próxima vou lá estar!

It has finally happened! It’s great news to see AmigaOS free from it’s legal disputes! Hyperion seem to now have full rights to develop it for whatever hardware platform they desire.

I hope they give the OS a clear roadmap, even if it is primarily targeted to a niche market (like the embedded one, where I think it could have some following). And I also hope they realize that their most probable early adopter userbase will be us Amigans. We nerds that had Amigas 10-15 years ago, and that now have twice that age at least. I think they need to target us first.

Like I’ve seen the honorable Zetr0 say on EAB, the boing ball is on their side now. Let’s see what they do with it!

I’ve been using my company’s paper calendar (the ones they distribute) to mark my project’s research, development schedules, deployment phases, support events, appointments, personal events, holidays, whatever. I like to have a view of the whole year; visualising the months ahead is great to preview stuff, but looking back at the past months is great to see where you’re at.

Amazingly, I can’t get this view in Apple’s iCal, the further it goes is one month view. This means I’ve nerver used it. I’ll be looking at other software alternatives (as soon as I can find the time to do so) and see if I can move away from paper… any sugestions?

Bolas, não tenho tempo nem para me coçar… entre a construção da casa nova e o trabalho só me sobra um bocadinho de tempo para tratar da minha raposita… e mal chega.

Apreciem: tenho na cave dois Spectrum +2 e um Amiga 1200 que comprei no eBay. Ainda não os testei sequer! Isto não é normal…