PIC-based Central Heating Controller
Central heating systems has been a good solution for many homes and even offices for quite some time now. If you own such a system I’m sure you would like to be able to control it remotely from your bed or even from a computer. This project presents such a controller. It has a 5/2 days programmer, that is 5 week days, 2 weekend days or for entire week.
The control panel allows you to turn on and off heat and hot water independently. It has 10 program entries that you can save and you have the possibility to manually override the program. Basically it is composed of two modules: the relay module that is placed at the boiler, which also has the 9 pin D connector for serial connection and the programmer panel which is connected to the relay module by a UTP cable.
The programmer panel has a 2×16 LCD display and five switches to select the desired program or manually control the central heating. PIC16F628A microcontroller was used in this project as the system’s brain. Dallas DS1307 was used for time management and for saving time settings in its memory. It is powered by a backup battery so it will not lose the memory data when mains power is taken. Max202 IC takes care of the serial communication.
Because of the UTP wire lenght the rellay output of the PIC can not drive the rellays directly, so a driver is used from Quasar Electronics. It is also a good idea to use protection diodes on those outputs to take care of spikes.
LCD will show the current operation mode for central heating and hot water, the on/ off state and the time. Switch 1 and 2 turns the system on/off , switches 3 and 4 are used for manual control and switch 5 is used for programmer setup. A detailed explanation of the programmer’s operation is presented in the link with all schematics and construction procedures as well as the software for the microcontroller.
PIC-based Central Heating Controller: [Link]
June 16th, 2009 at 6:34 pm
Funny. Every time I read a post online dealing with control of mains wiring, there’s always a disclaimer saying, “If you try this project, you might either kill yourself or burn down your house. Proceed with caution and I’m not responsible. yadda yadda yadda
Why is it then that someone can put together a homebrewed thermostat and it’s not subject to the same disclaimer? I find it amusing – if anything could burn down a house, it’s a mis-managed heating system, imho.
June 16th, 2009 at 6:47 pm
I think it’s a general disclaimer and people should not try to do anything at home if they don’t know what they’re doing. It’s always recommended to try these things under an expert supervision, or at least someone who knows he’s away around electricity and electronics.
June 16th, 2009 at 9:08 pm
Yes Signal7 it is amusing, however the disclaimer keeps the author of the project from away from the court in case some accident happens. The project deals with mains wiring so it’s pretty dangerous. If you watch Stupid Behavior Caught on Tape you would be amazed what some people do/try at home…