Early-2019 note: Still alive! Living in an apartment so not much home hacking to do. I shall return.

hvacMonitor

A small project to monitor and control my HVAC system. Designed a PCB... need to get it critiqued!

Hardware is a WeMos D1 Mini, a few DS18B20 digital thermometers, and 4 relays. I started out with an ESP-01 but, as always, I wanted more! Check out the board design here.

Features

• Arduino code running on a single WeMos D1 Mini.
• Monitoring of the air temperature coming into my HVAC unit (return air) and temperature of air after it's cooled/heated (supply air), including a Blynk notification if the unit isn't performing. All temperature sensors are Maxim/Dallas DS18B20... a mix of probe-style and bare TO-92 package sensors.
• Monitoring of HVAC run status. This is done by tapping the 24VAC t-stat with relays (NTE R14-11A10-24(11)) to give the WeMos dry contacts to monitor. The Blynk app displays if the HVAC is on or off, and how long it's been on or off.
• Sending RA/SA temps and run status to a Phant server on a Raspberry Pi in lieu of data.sparkfun.com (which had uptime issues):
  • Install Raspbian and Node.js using Dave Johnson's fantastic guide.
  • Install Phant with sudo npm install -g phant
  • Because of this issue:
    • Run sudo git clone https://github.com/stoto/phant.git to download fixed files (thanks stoto!)
    • Run gksudo pcmanfm to open file manager as root, allowing for drag and drop.
    • Copy/overwrite the content of stoto's /phant/lib into /usr/lib/node_modules/phant/lib. If this folder doesn't exist, check /usr/local/lib/node_modules/phant/lib.
    • Run phant.
    • Edit home.handlebars at '/usr/lib/node_modules/phant/node_modules/phant-manager-http/views' if you'd like to keep your streams from prying eyes.
• All data that needs to survive a hardware reset is stored to Blynk virtual pins, then synced back after a reset.
• OTA Updates: Using BasicOTA. Learned from this post that a complete power down is required after uploading BasicOTA for the first time. Weird, but whatever. Thank you Ivan!
• 4-channel DC 5V relay switch module (source) providing control of cooling, heating and fan-only modes.
• Future: Replace 24VAC dry contact relays with current monitoring via a SCT-013-030 current transformer (for HVAC run status).
• Future: Air quality monitoring with a true laser particle counter (ideally 2 size ranges (>0.5 & >2.5 microns)). Either in-unit to monitor filter efficiency, and/or exterior (outdoor) and indoor AQMs that prompt for fan-only HVAC operation to utilize MERV 13 filter for air cleaning.

Libraries and Resources

Title	Include	Link
Time	Timelib.h	https://github.com/PaulStoffregen/Time
SimpleTimer	SimpleTimer.h	https://github.com/jfturcot/SimpleTimer
blynk-library	BlynkSimpleEsp8266.h, WidgetRTC.h, TimeLib.h	https://github.com/blynkkk/blynk-library
OneWire	OneWire.h	https://github.com/PaulStoffregen/OneWire
Arduino-Temperature-Control-Library	DallasTemperature.h	https://github.com/milesburton/Arduino-Temperature-Control-Library
ESP8266 board mgr	N/A	json & instructions

Many thanks to all the library authors. I know nothing. They do.

Pin Assignments

HW Pin	GPIO†	Purpose
A0	A0	Available (todo: current transformer).
D0	16	Fan control relay (green wire††).
D1	5	Cooling control relay (yellow wire††).
D2	4	Heating control relay (white wire††).
D3	0	T-stat control bypass relay.†††
D4	2	Available.†††
D5	14	HVAC fan-only run state.
D6	12	DS18B20 array. 4.7KΩ pullup.
D7	13	HVAC cooling/heating motor run state. 10KΩ pullup. Future: Split these two states.
D8	15	Available.†††

† ESP8266 GPIO: The pin number used in the IDE.
†† Wire colors correspond to standard HVAC thermostat 4-wire system.
††† About ESP GPIOs and boot modes.

Testimonials

From friend:

Cool, man.

From kids:

What is that?

From wife:

That's nice, honey.

From me:

It's great to have historical data on outside temperatures and see how they impact the inside, as well as notifications if the return air/supply air delta temperature drops too low or is trending that way. I can at least get a jump on possible refrigerant loss, compressor overheat, or other service issue. I can also set any room's temperature sensor to be a virtual thermostat... from my phone. ZONES! Go team.

How to edit this.