Home -- Design -- Electronics -- Build -- Notes -- Analysis
The original Waeco Adler Barbour Cold Machine Board F-1886 Rev2 used on my boat's refrigeration system burned out. It has failed several times, and from the beginning, and over the 17 years I have had the boat, I have jury rigged solutions for controlling the temperature of the freezer, having indicator lights that I can see, and so forth.
The compressor is a Danfoss BD50 and uses the typical 12V Inverter Module to actually run the compressor. For many years I fought with water cooling the refrigerator, but after changing many hoses and pumps, over and over, I decided to just let it be air cooled.
In any case I have decided to trash the original controller board and wiring harness, and build my own ESP32 based Thermostat and Controller using my myIOT architecture to also provide a consistent WebUI and remote monitoring capabilities.
The circuit will NOT include a relay to control a water cooling pump, but that could easily be added.
Unfortunately there are no schematics of the Danfoss Inverter and so I have had to reverse engineer it's behavior empirically. I have two different units. There is an 101N0212 currently on the pump. I also have a spare 101N0220 I used for reverse engineering on my desk (without a compressor).
The documentation of the fridgeController is broken up into several pages:
- home - this page, which includes an Overview of the design
- Design - detailed design, including parameters & behavior
- Electronics - circuit schematics and PCB's
- Build - 3D printing, assembly, and installation
- Notes - Implementation Notes for the fridgeController
- Analysis - A detailed analysis of the 101N0212/101N0220 Danfoss/Secop Inverter behavior.
Physically, I have decided to break the physical design into two circuits. Each part will have a PCB and a 3D printed box..
The first part is the miniBox which is relatively simple, and which will sit atop the inverter in a 3D printed enclosure. The second part will be the more complicated ESP32 based Controller which will live in a kitchen cabinet and have an external WS2812b LED.
The miniBox is intended to remain in place and be testable, and nominally usable, without the controller being present. It allows the compressor to be run via 2 switches, at low or high speed in the event the ESP32 based controller fails, or is not present (i.e. in development or being repaired). It has the following connectors:
- has a 2 pin Phoenix plug for 12V input from the inverter's main BATT+ and BATT- terminals
- has a 2 pin Phoenix plug for FAN+ and FAN- output to the 12V 0.6A FAN
- has a 6 pin JST connector for input from the other 6 terminals (FAN/DIODE+, FAN-, DIODE-, C, P, and T) from the inverter
- has an 8 pin JST connector for output to the ESP32 based controller
The miniBox has three indicator LEDs
- GREEN to show when the inverter box generally has power.
- YELLOW to show when the FAN is on.
- RED for the flashing diagnostic diode.
The miniBox has two switches that allow the compressor to be run in an emergency, in the absence of a controller, or generally, to override the controller.
- OVERRIDE - Turns the pump on, overriding the (possibly missing) controller.
- LOW/HIGH SPEED - Controls the speed of the compressor if OVERRIDE is turned on.
As mentioned before, the compressor can be run and used with just the miniBox. In the event that it fails for some reason, it may quickly be removed, and as long as the main 12V power supply to the inverter is supplied, the compressor can be run at low speed by merely shorting the T&C pins on the inverter.
The Controller sits in a cabinet out of view. It is based on an ESP32 and has WIFI Connectivity The Controller has the following connectors:
- a 2 pin JST connector for the 12V power supply input for the Controller.
- a 6 pin JST connector for the other 6 pins of the 8 pin cable from the miniBox.
- two 3 pin JST connectors for connecting DS18B20 temperature sensors
- a single 2 pin JST connector for connection to an optional mechanical thermostat
- a 3 pin JST connector for output to external WS2812B LED*s that can be mounted on the controller, and/or outside of the cabinet for a general visual indication of the state of the system and inverter/compressor.
Initially the Controller will be powered by breaking the BATT+ and BATT- wires of the 8 pin cable from the miniBox into a separate 2 pin JST connector. Later, if so desired, the Controller can be powered by a separate connection to the boat's batteries so that the Inverter power supply can be turned off and on as needed without necessarily rebooting the ESP32, thus allowing the Controller to detect and alert me to refrigerator power problems,
The Controller generally has a number of physical features:
- on/off switch
- 16x2 character Blue LCD display
- an SD Card for storing refrigerator history and logfiles
- three buttons for direct programming of the Controller
- four indicator LEDs (green, yellow, red, and blue)
The Controller can be programmed (temperature cutoffs, general configuration) using the 3 buttons and the LCD screen. In addition, or perhaps primarily, though, it will have a Web User Interface that can be accessed from a phone, laptop, or other programs on the boat's LAN, and will function as a myIOT device.
This project directly makes direct use of my MyIOT ("my internet of things*) repository, which provides a generalized approach to building relatively simple parameter driven ESP32 devices that include a Web UI.
The PCBs (printed circuit boards) were milled using the cnc3018 CNC machine that I built.
I hope you will take a few minutes to check out some of these other pages too!!
This project directly relies upon the public open source Arduino development system, the Espressif ESP32 online documentation and additions to the Arduino IDE, as well as a number open source Arduino libraries
I would like to thank the countless individuals who have contributed to making these development tools, source codes, and documentation available for free public use, including, but not limited to:
- KiCad
- FlatCAM by Juan Pablo Caram
- Arduino IDE and Libraries
- Espressif Systems
- Adafruit NeoPixel Library
- jQuery, Bootstrap, and the jqPlot javascript libraries
This program, project, and repository is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License Version 3 as published by the Free Software Foundation.
These materials are distributed in the hope that they will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR ANY PARTICULAR PURPOSE. See the GNU General Public License for more details.
Please see LICENSE.TXT for more information.
Next: A look at the detailed design of the fridgeController ...