HackSpace_-_April_2020

WiFi heater upgrade with NodeMCU

TUTORIAL

hile some heaters have

built-in thermostats, they’re

often very inaccurate and

will stick in the 'on' or 'off'

position. This makes the room

temperature unpredictable, and

can lead to a nasty shock when the electricity bill

comes in. It can also have unfortunate side effects

for 3D printers and temperature-sensitive tools. This

project uses a NodeMCU and thermistor to measure

ambient temperature, and control an electric heater

accordingly. Using a NodeMCU for this project is

cost-effective, but working with the limitations of

the board can be tricky when dealing with multiple

analogue inputs. The NodeMCU only has one

analogue input available, and to use multiple devices,

you’ll need to discover how multiplexing works, and

learn a few tricks about controlling relays and sensors

using an ESP8266 web server.

WINTER IS COMING

The simplest sort of heating controller is a dial fixed

to a wall. Turning the dial to the left usually makes

the room cooler, while turning it to the right makes

it warmer. Most people are familiar with this sort of

control, and they know instinctively how to use it. It’s

resilient, easy to clean, doesn’t need a fancy digital

display, and you don’t have to press multiple buttons

to change any settings. Controlling this sort of dial

over the internet poses a bit of a problem, because

W

Read multiple analogue inputs and control your electric heater over the internet

WiFi heater upgrade

with NodeMCU

BE AWARE OF RISKS

This project involves connecting to and switching

mains electrical voltages, and there is a risk of injury

or death if you don’t know what you are doing. Never

work on a live electrical circuit; always make sure you

use appropriate fuses, breakers, earth connections,

and other safety features in your project. Make sure

that there are no exposed electrical connections, and

take care that there are no places where an electrical

short could occur between the high and low voltage

portions of the project. Alternatively, you can use a

pre-built solution. There are some smart sockets that

work with WiFi-enabled microcontrollers, and these

allow you to avoid any mains wiring.

You also need to make sure that, in the unlikely

event that the heater gets stuck on full, it's not going

to start a fire before you have chance to fix it.

Dr Andrew Lewis

@monkeysailor

Dr Andrew Lewis

is the owner of

Shedlandia.com, a

restorer of old tools,

a fabricator for hire, a

research scientist, and

a founder member of

the Guild of Makers.