Remote Aircraft Heater Controller

This is an IoT implementation of the remote control of an aircraft block heater. In my case, there is no WiFi, thus a cellular method is used. I previously developed this approach using an Adafruit FONA 800 Shield. With the progression of technology, this 2G cellular device is no longer supported by most cellular networks as of 2020. I looked a a number of approaches and found the Particle.io product Boron an excellent replacement device. The SIM card is part of the device, but also lets you put in your own. It is easy to program and has great support for the maker community.

Design

I started with the bones of my previous Remote Aircraft Heater Switch. I changed the design by removing the FONA800 and replacing it with the Boron. I also added a DHT-22 temperature/humidity sensor, hay, just because. I reused the AC plug/socket, box and relay. Note that the Boron is a 3V device and cannot be directly connected to other 5V devices without a voltage level shifter. I used this to connect to the relay and ensure enough current for the relay interface. I also added a monitor of the 5V USB voltage. A pair of 4.7k resistors divided the voltage in half to feed the 3V device.

You should use a miniswitch connected between the battery and Boron. Turn it off when you are not using it since it will drain the battery which isn't a good thing. I'm using a 1200 mAh LiIon battery. Be sure to check the polarity of the battery connector, mine needed to be reversed. The battery will carry the device through any brief power outages. My program records when it was plugged in and the time of any outages.

Here's a picture of it in use.

Boron Interfaces:

• 5V USB power to Boron board connector
• GND to Ground
• Relay to level shifter Hi side
• Level shifter low side to Boron D2 for relay control
• 3V to 5V level shifter voltages to 3V3 and VUSB
• DHT-22 Data pin to D4 (optional)
• 3V3 to A0 (for monitoring only)
• Center of 5V resistor divider to A2 (for monitoring only)

Parts List

• Particle Boron
• 1200 mAh, 3.7V LiIon battery
• uFL Cellular antenna (comes with the Boron kit)
• DHT-11 Temperature/Humidity sensor (optional)
• 5V Relay Module
• AC plug cord
• 2x 4.7k resistors
• AC socket
• USB power supply
• USB power cable (comes with Boron)
• SPST Miniswitch

Software

Coding must be done with Microsoft Visual Studio Code (free). The Arduino IDE cannot be used. There is a Particle,io extension to Visual Studio Code that supports their devices. RemoteHeaterControl.ino is my current working version. The code is well documented. You will probably find the need to add/modify/remove some parts to fit your design.

Operation

Commands are sent either from your Particle.io console or a Particle.io smartphone app. The command functions are:

• Set Relay
• ON
• OFF - Turns it off and cancels the timer
• SET - Turn on the timer using the Start and Stop times. It can only be set for a future time less than 24 hours.
• Start Time (UTC)
• Stop Time (UTC)