I’ve had a lot going on over the last few months, and among the bustle Neutrino has gone through several iterations. The baseboard is currently at version 3.2, and the sensor at 4.1.2. Some of the key changes include building the radio onboard both devices, pcb antenna on the sensor, changing to a better battery clip, adding pads to support the BME280 (when it becomes available, it can replace both the SI7021 and BMP180. It can save money if it costs less, and possibly power with one less device). The base now has a microcontroller onboard, which handles the relays and LEDs. This allows it to be functional standalone as a relay board, though the radio is not integrated into the microcontroller portion. The base still interfaces with either beaglebone black or raspberry pi, and the microcontroller is reachable via serial and programmable via avrdude gpio programming. The microcontroller is powered off of 5v, and as such level shifters have been added to interface with the beaglebone. I initially was able to run it off of 3.3v, but the microcontroller is essentially overclocked in this mode, and I wanted it to be reliable.
In the past two months I’ve changed jobs and moved to another state. This home has two floors with a two zone heating system. It’s winter, and we found that the kids’ rooms were very cold. Neutrino to the rescue! I installed a sensor in all three rooms, and the following immediately became apparent: 1) The master was usually ~3 degrees warmer than the other bedrooms. 2)When the downstairs and upstairs were both calling for heat, the upstairs rooms heated evenly due to the CFM being spread out among the whole house. In this mode the upstairs rooms eventually equalized 3) When only the upstairs called for heat, the master got heated much more quickly than the other rooms. This was a problem because the master has the upstairs thermostat, and we want to turn the heat down in downstairs zone at night. In doing that, the other rooms would slowly drift to being ~5 degrees colder throughout the night.
On the first night it was installed as a controller (instead of just passively collecting data), we drove the upstairs heat off of the average temperature of all three rooms. This was a marked improvement. It maintained the ~3 degree difference between rooms, but put a floor on how cold it got in the kids’ rooms. It also meant a little extra heat for the master, but no big deal, we essentially split the difference between the rooms. After the data from that night was collected, we closed the vents in the master half way, and that seems to have helped significantly. The heating is now a bit more even, regardless of which zones call for heat.
I’ve learned a few things in this new home. The first is that zoned systems seem to need Neutrino MORE than non-zoned. I had initially built the thing as sort of a poor man’s alternative to zoning, but a multi-zoned system has interesting dynamics going on, and an increased complexity in how the home heat is distributed when running in various modes. As such, one needs a way to see that information in order to tune the system, or bad things can happen. It could probably be remedied with trial and error, but having the data helps a lot. For example, my wife noticed that having the downstairs heat on made the bedrooms more evenly warm, so suggested we try leaving the downstairs heat on. I, on the other hand, surmised that the heat from the first floor was rising into the master (with our door being open and the thermostat nearby) and artificially raising the master’s temperature, thus we should turn the heat off downstairs at night. It wasn’t until we had the data that we realized that the downstairs vents being on reduced the CFM in the master to the point that the bedrooms would heat evenly if both zones were running.
I’ve ordered manufactured prototypes, 10 bases and 10 sensors. I feel that the software needs a bit more polish, but eventually I’d like to start offering the boards as dev kits. I want to have software that will run, but I also think it would be far better if others could pitch in. I can do it all myself, but I know there are people better than me at the various aspects, particularly UI.
You’ll notice here the sawtooth, it’s due to only being able to turn the furnace on or off. We’d need variable fan speed and a furnace capable of efficiently producing lower temperatures to even that out. Neutrino actually has a ‘hysteresis’ setting to decide how big the sawtooth will be, here it heats to 1.5 degrees above the low setting before kicking off. I could set it lower for a smaller sawtooth, at the expense of the furnace kicking on and off more often, but it’s surprisingly comfortable as-is, and more consistent than the stock thermostat.