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Thermostat V3 Schematic

Posted 2012.06.19 9.45 in Computers/Internet/Technology, Hobbies

Here is a schematic for my Thermostat V3. It’s something of a ‘block diagram’ as I did for the ISEB6 layout, as it is another project that was mostly assembled from off the shelf modules.

You can download the PDF version here.

I have omitted the lux / luminosity sensor in the above schematic, because it’s not working very well and I find it’s fairly pointless. I’ll likley remove it from my thermostat next time I’m doing work on it.

For something of a BOM and assembly instructions, please download the zip file that was linked in the original Thermostat post.

Cheers!

Thermostat Three

Posted 2012.05.09 21.27 in Computers/Internet/Technology

This might just be the fastest project I’ve ever done. Saturday morning I started the hardware build, by Saturday evening I had also begun the software. By Sunday afternoon I was halfway through. Sunday evening saw it 90% completed. Monday was finishing touches and adding some extras just because. Tuesday I finished it. This afternoon I installed it.

Some of the things that aren’t obvious in a still photo: The the block above the screen has two RGB LEDs behind it. These aren’t programmable, but one cycles through the colours slowly and the other does so quickly. Together they provide a sort of swirly multi-colour effect that I think is reminiscent of ST:ToS effects.

The red circle ‘red alert light’ is wired to the XBee’s RSSI so when the XBee receives a wireless command, the red light comes on for a few seconds.

The white gridded rectangle is the DHT22 sensor (temperature and humidity). I felt it would ‘blend in’ enough that it should be mounted right up front for all to see. The little black hole to the right of the DHT22 is for the light sensor.

Why is there a light sensor? Why not? Also: because I had an extra one laying around.

The screen display is mostly self-evident. Time, day, date. Heat/Cool. Run/Hold/Override. Target temp (small) and actual temp (large). Fan status (on/auto) and humidity.

The last line is EV (exposure value) and free memory. That’s 657 bytes. Not kB or MB, just bytes. It probably won’t ever change but it’s there just because there was space for it.

The following images have some more build details / information:

The sketch code, and a text file with lots of my design and build notes, can be downloaded here: Thermostat_3.zip

Another Work In Progress

Posted 2012.05.06 16.47 in Computers/Internet/Technology

Because I can have more than one project on the workbench at any given time. The more the merrier! Though I really ought to actually complete something eventually. I guess.

Anyhow – the Sneak Peek project from a few days ago is on a very brief hiatus as I await another component or two, so I thought Hey! I should build another thermostat!

The original was kind of drab and beige, with a lot of sloppy workmanship. Version two is sleek and translucent, and the workmanship is a little nicer. Version two looks very technical, with exposed circuitry and insides.

The problem with #2 though is that it didn’t cover all the holes and paint-outlines from the original antique non-DIY thermostat. So in order to hide the holes and mismatched paint, the obvious solution was a thermostat with a larger footprint. Making it super-geeky and sexy is just a bonus.

See, I had this Star Trek thingy from Think Geek, but it’s sound effects were really annoying and useless. Pretty though – a perfect enclosure for some kind of project. Toss in an LCD and some sensors from Adafruit, and an Arduino Pro from Sparkfun, and voilla – Thermostat!

I just need to wire in some relays and then it’ll be ready to hook into the house’s HVAC system. Maybe another week or two (unless I get distracted by something shiney) then I’ll post a detailed write-up and code.

Master Control Project

Posted 2011.12.25 9.40 in Computers/Internet/Technology, Hobbies

Last weekend I finally mostly-finished the project I’ve been working on, on and off, for the last several months. My Master Control Project, or MCP*, was designed to be a central controller and information display that would sit on my desk in my livingroom, and give me all sorts of useful information while allowing me to control various things.

The idea grew out of my DIY thermostat project – after getting a taste of what could be done with an Arduino and an ethernet connection, I wanted more!

Plus, the thermostat is located up on a wall and I can’t see it from my desk in the livingroom . I wanted a cool project that I would be able to see all the time!

Unlike previous brief glimpses at this project, this time around I’m going over the whole thing in detail – mainly because it is, as I said, mostly-finished. (It’ll never be fully finished, because I’ll always be adding to it.) The other reason why this is a good time for a write-up, is last weekend was when I rebuilt the whole thing from the ground up, and took the project from ‘beta’ to ‘1.0’.

Thermostat 2.0

So here’s what it does so far:

  • It is a clock, with full day / date and time display.
  • It mirrors the HVAC information from my DIY thermostat.
  • It displays the current temperatures of my two aquariums.
  • It controls the lights of my two aquariums, turning them on and off automatically.
  • It controls my Game of Life wall display, turning that on and off automatically.
  • It displays the amount of background radiation detected by a geiger counter.
  • It displays the number of active connections on my linux server.
  • It displays the current weather conditions for my area.
  • It allows me to directly override the thermostat, aquarium lights, game of life display.

For communication, the MCP is connected via ethernet to my LAN, and also has an XBee wireless module allowing it to communicate with other devices in and around my house (eg. the thermostat).

Pile of Parts

For the most part, the MCP is made with off-the-shelf components. Some components were kits, some came fully assembled, and a few things were ‘homebrewed’. Here’s something of a BOM:

  • Arduino Mega 2560 – the brains of the operation.
  • Arduino Mega Proto Shield – provides connections for I2C (secondary LCD and Chronodot), Serial (XBee), the geiger counter, and the GLCD.
  • Arduino Ethernet Shield – does what it says on the box, this adds 100/10BaseT ethernet, allowing the MCP to receive data and commands from clients on my LAN or out on the internet.
  • Arduino Patch Shield – provides simple plug-in connections using normal Cat-5 cable so you can easily access inputs and outputs some distance from the main unit.
  • KS0108 Display – a monochrome graphic LCD that can dispay text and images.
  • Chronodot – a highly accurate RTC with its own battery backup and an I2C interface.
  • Protoboard GLCD backpack & Wiring Harness – some standard proto-board and ribbon cable, to connect the GLCD and Chronodot back to the Arduino, via the Mega Proto Shield.
  • 20×4 LCD Display – a monochrome LCD character display, for displaying text-only.
  • Adafruit I2C LCD Backpack – an Adafruit kit that lets you use character LCDs using I2C.
  • XBee – a transceiver that lets you communicate with other devices using standard serial protocol, wirelessly at ranges up to hundreds of feet away.
  • Adafruit XBee Adaptor – an Adafruit kit that makes it easy to use a 3.3V XBee module with a 5V Arduino.
  • MightyOhm Geiger Counter – a self-contained geiger counter kit that is easy to interface with an Arduino, and has a fairly sensitive GM tube.
  • Adafruit Perma-Proto Board – an ingenious proto-board from Adafruit, which lets you transfer projects from a breadboard to a soldered, permanent format.
  • Waterproof DS18B20 Temperature sensors – submersible digital temperature sensors, they only require one digital line and you can put more than one sensor on a single line.

The MCP is mostly assembled in layers, each layer is a ‘shield’ using the Arduino lingo. Here are the assembly steps:

The MCP is installed on the upper part of my desk, above the primary display of my computer. This puts it just slightly above eye-level, almost at the centre of my ‘hub of activity’. I spend most of my home-hobby-time at my desk, where my computer and tv are located.

This shot shows the MCP installation, with all its peripherals and cables etc. The modular construction means that if any part fails or needs attention, I can easily access and isolate that part, or replace it if necessary, while leaving the rest intact. And all without desoldering anything!

In terms of software, the whole thing is running with a sketch written in the Arduino IDE. It compiles to a binary of about 47kB in size, and generally uses about 3kB of RAM while it’s running. Prior to last week’s rebuild, I updated the sketch to version 1.0 of the Arduino platform.

The libraries used include:

I’ve added some special characters to the GLCD font definitions, such as the degrees symbol, and used a few graphic symbols as well, such as the fish and snail icons. A couple of the indicators on the GLCD are ‘text’ but I’ve used a graphic to squeeze the text into smaller area than the standard fonts would allow.

For all that I’ve got completed though, there are still some significant aspects that I have yet to include. The most-glaring omission is the lack of any kind of controls on the MCP itself – there are no buttons or switches or anything. I can’t control the Master Control Project, without firing up a terminal and accessing it over a network connection.

On the one hand, this isn’t a huge problem as it needs very little ‘help’ in doing its job – the aquarium lights turn on and off when they should, my Game of Life display is on when I’m around to enjoy it and off when I’m not. And the various data displays show me what I want to see.

However, it would be nice to have some buttons or something, so I could override things quickly and easily. I have some ideas on how to do this, and have already explored some options – touchscreen, rotary control, buttons, etc. Sooner or later, I’ll make a decision and put something into place.

Another obvious step will be a proper front-panel, so that the LCD displays aren’t just haphazardly screwed into the edge of the desk shelves. I’m planning to get a laser-cut acrylic panel made, which I think will look quite snazzy – but I need to finalize my plans on the buttons/controls first.

I’m also toying with the possibility of upgrading the displays. Obviously the GLCD wasn’t enough, hence the added 20×4 character display. Even that feels cramped, so I’m looking at the option of a second 20×4 display… Or maybe there’s some way to replace both of these displays with something all-together bigger – like a little VGA screen.

I have one of those digital photo frames, that I mean to disassemble and see if there’s any way to merge it to an Arduino… but that’s way down the road.

For now, the MCP is ‘done’ and it’s done well enough for me to leave it alone for at least a little while. Should anyone be interested in having a closer look at the ins and outs, I’ve attached a zip file containing the Arduino sketch, the related headers, and a text-file which contains my overview and some wiring and design notes.

Click here to download the MCP zip file.

(* Yes, I’m a fan of the original TRON movie. Not long after I started this project, I couldn’t help calling it the MCP and the name just stuck.)

Slow Progress

Posted 2011.06.19 20.36 in Computers/Internet/Technology

I’ve been working now and then on my Next Project. It’s slow going but there is progress happening.

This weekend I added a power supply (boring) and a radiation sensor (interesting). The radiation sensor is basically a geiger-muller tube detector. Instead of making audible tick sounds, I modified it to flash a blue LED whenevever it detects ionizing radiation. The counts are tabulated by the MCP’s microcontroller and available as a cumulative counts per day or current counts per minute.

What else can it do?

  • It is a remote display and remote control for my Thermostat.
  • It controls the lights in my aquariums.
  • It monitors the temperature in my aquariums.
  • It controls my Game of Life display.
  • It monitors and displays outdoor weather conditions.
  • It notifies me of activity on my home file server.
  • And now it monitors ionizing radiation.
  • It allows me access to all of this information and all of these controls both in-person and via network.

So I can monitor and control any of this stuff from my iPhone, iPad, at home or at the office, or anywhere.

The main board is an Arduino Mega. It’s using an Ethernet shield and an XBee shield. The radiation sensor is next to the Arduino. The display is a ks0108 glcd. More geeky goodness will be coming next week.

Back in Business!

Posted 2011.04.18 21.25 in Computers/Internet/Technology

The parts I needed arrived today, so it was just a matter of asembling a new ‘motherboard’ then wiring it into the thermostat enclosure.

The parts were mainly the circuit board and the ATMega328p chip, along with the sundry support electrics. To be honest, I’m using the SparkFun Serial LCD kit — for $25 it’s almost a complete self-contained mini-Arduino that piggybacks onto the back of a 16×2 LCD display. And it even includes the LCD!

If I knew how to use Eagle and if I had more time, I’d have made my own PCB design. I still might do that as I now have more LCD screens than boards to slap on the back of them. The SparkFun Serial LCD isn’t perfect, but it’s actually quite close.

So my DIY networked Thermostat is back up and running with a shiney new brain, my house is once again comfortable, I’m out of the stone age and back in the World of Tomorrow, and I’m a happy camper.

And just for kicks, I took the old dead board and tossed it in the dishwasher, ran a load on ‘heavy-duty pots-n-pans’ mode, and the darn thing is actually working again. Go figure! I won’t trust it in mission-critical use, but I can certainly use it for prototyping or making stuff that’s not, you know, directly wired into my friggin home.

Yep, once again all is right with the world.

Grumble Grumble

Posted 2011.04.16 13.45 in Computers/Internet/Technology

Well my parts order did not arrive Friday, so I won’t be able to get the thermostat rebuilt today. Grumble grumble grumble. Should be in on Monday though and I ought to be able to slap it back together Monday evening.

In the meantime I’ve torn apart the remains of the old one and I suspect I know what killed it. Grumble grumble grumble. A while back I learned about solder with water-soluble flux, and I thought I had ranted about how it screwed up a number of little projects. I can’t find that rant now but suffice to say, I detest that stuff.

Anyhow, so it turns out that the water soluble crap is still haunting me. The board that ended up being used as the brains of my thermostat was recycled from a previous kit, and that kit had been assembled before I learned about the perils of water-soluble flux. So it was doomed to failure before it even became a thermostat, I just didn’t realize it. Grumble grumble.

Staying positive, I’ve at least learned a few more things, and the thermostat will definitely be back, better than ever. And this time, with plugs and sockets, so I can easily pull the darn thing apart if needed.

Another nice thing is that although this little misadventure did piss me off, it hasn’t tipped me back towards depression or that sort of thing. I’m just rolling with the punches and moving on.

So just a couple more days living with the antique cave-man thermostat, but after that I’ll be back in the 21st century again.