Home thermostat using nixie tubes and neon lamps for the display

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A project build a better thermostat. It sports the ATMega1284 processor, 2 panasonic opto-isolated solid state relays, batery backed up real time clock, 4 digits for time, 2 digits for temperature, 10 neon bulbs for various status indications. The source code will be open source and the hardware details will be available. Not sure of it's licensing. It uses the arduino libraries, though it does not use the arduino development kit. It has a main() function, though in the end, it consists of a setup section of code followed by a big loop, just like the arduinos.

Sadly, this thermostat died a quiet and peacefull death and has now been replaced with the NixieStat-ESP:

The project is off to a good start this year. I gave it a case which my wife likes (very important). I am working to make the user interface usable (the keyboard shown in the picture). I have added a menu system using the the serial port.

This current version is actively controlling the heater of my house. My house has a hot water radiator system. I have the thermostat use the outside temperature to control the temperature of the radiator. I use a sensor for the inside to fine tune the radiator's temperature using a pid algorithm. The room I have it in (the one with the sensor inside) fluctuates less than 1 degree. The other rooms are at whatever temperature they are at (as with any single sensor thermostat) but they are comfortable because they do not fluctuate much either. My radiator pipes are always warm ;)

Do you want a KIT of one of these for yourself?

I would like to do a kick starter project to fund a parts buy. I need to get an idea of how much interest there is in this project. The kit will be a full set of parts and PCBs and an assembly manual. I am currently thinking of offering two varieties. The first is the Nixie Tube version shown in the pictures. The second will be an LED based version which will have the same basic look, but using 7 segment LEDs displays and individual LEDs instead of nixie tubes and neon bulbs. The LED version will free up some board space on the processor board which will be made into proto-board space.

Some interesting turns I can take on this is to also provide an LED version which will be about 20 - 30 dollars less and have more breadboarding area on the PCBs. It will have the same basic look, but instead of the nixie tubes it will have 7 segment displays.

Currently I am looking at 50 of each version and 20 assy manuals and boards. The kits will cost about $115 for the LED version and $155 for the Nixie version. The Manuals and boards will cost $20. These prices are approximate. In reality, wishful thinking says they will be less, Murphy's law says they will be more. I will need to play more with the spreadsheet to see what the costs will be for smaller numbers.

Here are a few basic specs:

- Supports up to 8 Maxim DS18S20 temperature sensors. Though the software can be changed to increase this number somewhat easily.

-It has 4 solid state relays (Panasonic AQH2213) that switch on the 0 crossing and can handle 900ma at 200VAC (assuming the board will handle such voltages, I only switch 24VAC now). These are for Heat, Cool, Fan and Heat pump valve. Though thanks to software they can be for anything

-Maxim DS1307 RTC for keeping the time during power outages.

-A standard HVAC interface though currently only heating and cooling has been implemented and on heat has had any real testing).

-A 2" x 4" (approx) proto-board for adding your own radio card to communicate with it. I am using a blue tooth board, but am not fully happy with it. I am leaving this to the imagination of the user. Wifi is an easy alternative.

-Operates on 12VAC - 27VAC

Some software features:

-GPL software. Not only will it heat your house, it will let you play!

-A clean menu system over the serial port. It was developed to be able to be used by a human or machine (cellphone maybe). Menu entries can be as simple as a single line of code to manipulate a value or the line a code and one or two functions to do more complex operations.

-A full logging system that can log temperatures and other stuff. It can fit a single temperature with a channel number (up to 32 channels) and a 1/4 degree resolution in 2 bytes. This allows me to log 2 days of data for 3 sensors, the on off transitions and the set point temperature.

-The code is based on the Arduino system and therefore uses many of their libraries, though it does not use the Arduino IDE, but instead uses a make file.

  • Updates to the display board and a little more

    Joe Croft02/01/2022 at 00:02 0 comments

    2nd whack on the display board. Not sure where my head was with the first try, the nixie foot print was wrong and the anode drivers were just all wrong.

    I still have a small fix on the cpu card itself, but I will hold that fix off for a bit. It was nothing an X-acto knife and a jumper didn't fix. 

    I will be submitting the board changes to github as well as changes to the code to ease configuration.

  • NixieStat ESP32 is now alive!

    Joe Croft01/17/2022 at 01:31 0 comments

    Finally have a working prototype for version 2 of the NixieStat. My older AVR based version sied last year so I updated it. Some might say over engineered it ;).

    This new version is an ESP32 based system with remote sensors. The system uses the Mosquito MQTT bus running on a RaspberryPI to handle feeding the data from the remote sensors to the thermostat itself.

    Since my first priority was getting a thermostat that would keep my house comfy, don't have a display for it yet. Since my nouse is now comfy, I am starting on the next step, the User interface.

    The source, including code and hardware drawing is now in The code resides in 2 repositories croftj/nixiestat and croftj/esp_components.

    Documentation is quite sketchy at this point but will hopefully get better as time goes on.

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