In my house there are several types of heat sources and they
are independent from each other and none of them are regulated, so it’s really
difficult to keep constant room temperature. Therefore I decided to add a
regulated heat source in to existing system. I find that the easiest
controllable energy is electricity, hence I end up with 2 kW power electric
To control it I decided to use “smart” connected
thermostat. Nowadays there are numerous devices that are made specifically for
this purpose, but they can be quite expensive and not always suit your needs.
So my solution was to build one and not only the thermostat but also automated
control system. The futures of this system can be expanded in the future.
As a main board I use Arduino Uno clone with the Ethernet
shield. As a power stage I use optically isolated relay module powered from
dedicated 5V supply. These relays are not suitable for switching high currents,
this is why I use another power stage with high current relays and MCBs (Miniature
Circuit Breakers). This protects system from over current and short circuit on
All the control electronics and relays get power from 24 V
DC power supply. To lower the voltage on Arduino side I use DC/DC step down
switch mode voltage regulator. It reduces voltage approximately to 9 V DC,
which is then fed in to Arduino’s Vin pin. The relay board is powered from
similar 5 V DC 3 A voltage regulator.
The system is
redundant taking in to account safety and future upgrades. For this project you
only need relay board with 2 relays or you can use other switching devices
(like FETs) to control power relays.
For temperature sensing I use DS18B20 temp sensor. I use it
in normal power mode so it is connected with three wires. In the future I will
add more sensors.
For security reasons I use wireless cloud-based camera, to
check if heater still in its place, is it working properly or is there any
other issue. When it’s dark in the room I use another relay to switch on the
LED light remotely.
Any wiring to the mains power should only be done by a qualified electrician!
4 channel relay board;
Temperature sensor DS18B20;
AC/DC 24V power suply;
2 x DC/DC step down switch mode voltage regulator;
3 x 16 A Miniature Circuit Breakers;
2 x power relays.
Triggering a relay according to temperature sensor measurements and set min and max temperature.
No Scheduling yet.