ESP8266 Walk-In Cooler Controller
Posted: Mon Dec 28, 2015 1:12 amI have been following this forum for a few weeks, but I have not had anything to post. I am now getting ready to wrap up a project so I thought I should share.
I recently started playing with the ESP8266 family. A couple of weeks ago I decided to start a project with the goal of running a walk-in cooler using a Window A/C unit. This is not a new concept as it has been done with a Commercial Product "CoolBot", and at least one other documented DIY project "ColdSnap".
Since I am using an ESP8266 12F for this project I decided to use a HTML monitoring and control. I am also posting the data to io.adafruit.com using MQTT. Right now the project is running on a breadboard. I should finish the frame work for the walk-in cooler. At that point I will be able to start testing the control algorithm.
The basic idea is use the ESP8266 to drive a heater attached to the thermostat bulb of the Window A/C. The heater in this case is a pair of 50 Ohm power resistor running from a 12V power supply. The resistors are driven with PWM through two GIPO outputs using TIP41 NPN FETs.
The software monitors three temperatures to set the heater control logic. The temperatures re measured with three 18B20 One Wire sensors. The three temperature points are The Cooler Temperature, The Cooling Fins, and The Thermostat Heater. The Cooler temperature is the primary logic driver. We want to keep the temperature at a set point. The A/C cooling fins are monitored to detect if the fins are freezing up. If the temp drops below freezing the fins are icing, at that point the heater to allow the A/C to defrost. The final temperature monitored is the Thermostat Heater. The heater temp is used to control heater temperature to within a few degrees of the point the A/C turns on or off.
I have uploaded the project to GITHUB, it can be found here:
https://github.com/bnorth12/CoolerController
I am sure I will keep tweaking the code, but it is close to a final product. It was nice to see that I can set up the ESP8266 as both a Web Server and Web Client in the same program.
Brian
I recently started playing with the ESP8266 family. A couple of weeks ago I decided to start a project with the goal of running a walk-in cooler using a Window A/C unit. This is not a new concept as it has been done with a Commercial Product "CoolBot", and at least one other documented DIY project "ColdSnap".
Since I am using an ESP8266 12F for this project I decided to use a HTML monitoring and control. I am also posting the data to io.adafruit.com using MQTT. Right now the project is running on a breadboard. I should finish the frame work for the walk-in cooler. At that point I will be able to start testing the control algorithm.
The basic idea is use the ESP8266 to drive a heater attached to the thermostat bulb of the Window A/C. The heater in this case is a pair of 50 Ohm power resistor running from a 12V power supply. The resistors are driven with PWM through two GIPO outputs using TIP41 NPN FETs.
The software monitors three temperatures to set the heater control logic. The temperatures re measured with three 18B20 One Wire sensors. The three temperature points are The Cooler Temperature, The Cooling Fins, and The Thermostat Heater. The Cooler temperature is the primary logic driver. We want to keep the temperature at a set point. The A/C cooling fins are monitored to detect if the fins are freezing up. If the temp drops below freezing the fins are icing, at that point the heater to allow the A/C to defrost. The final temperature monitored is the Thermostat Heater. The heater temp is used to control heater temperature to within a few degrees of the point the A/C turns on or off.
I have uploaded the project to GITHUB, it can be found here:
https://github.com/bnorth12/CoolerController
I am sure I will keep tweaking the code, but it is close to a final product. It was nice to see that I can set up the ESP8266 as both a Web Server and Web Client in the same program.
Brian