I think this means you need to be able to measure the temperature compare it with a setpoint and then turn 240v on or off. To read temperature in buildings I have used TMP36 devices in the past (usually with microcontrollers) and they are easy to setup and use, and cheap (see http://proto-pic.co.uk/tmp36-temperature-sensor/). However as idaadi points out you will need to organise some AtoD to read it. Since a relay seems like a good option to turn the power on and off (opto isolators may be another), Gertboard (having both ADC and Relays) would seem like a plan.rooster wrote:Hi
I've been using my RPi as a car computer and that's easy - just software! But electronics is like magic to me. I want to make my RPi control my heating system. It seems the easiest way is to take out my room thermostat (which is mechanical and just breaks the 240 V circuit when the temperature exceeds a set point) and replace with some sort of relay which is controlled by one of the output pins of the GPIO.
I know how not to electrocute myself and how to use a multimeter - and I did some soldering 20 years ago. But I need to know a) what sort of relay I would need b) how to control from GPIO c) how not to fry my RPi whilst doing it!
Thanks in advance!
Thanks - 2 gertboards ordered - waiting time 2 months I thinkidaadi wrote:From what I know , you need an external board to interconnect and use with the Rpi because there aren't any protections on the pins and you could damage it easily...
Second , to read anything you should need an Analog-Digital-Converter(ADC) present on that board , depending on what you want to implement.
For testing you can buy a gertboard and play with it , and then get one specialized on the tasks you want.
Thanks! I have a couple of temp USBs lying around which I might try but will follow your advice on the tmp36 sensors for when my gertboards come.I think this means you need to be able to measure the temperature compare it with a setpoint and then turn 240v on or off. To read temperature in buildings I have used TMP36 devices in the past (usually with microcontrollers) and they are easy to setup and use, and cheap (see http://proto-pic.co.uk/tmp36-temperature-sensor/). However as idaadi points out you will need to organise some AtoD to read it. Since a relay seems like a good option to turn the power on and off (opto isolators may be another), Gertboard (having both ADC and Relays) would seem like a plan.
Note that probably the most important thing to do is determine how many amps you need to switch and then check that your switching method can cope with this. Watch those wigglies, they bite.
I bought a couple of USB temp sensors of amazon a few years ago. Don't know the brand and I only got them to work on windows. Will update here if I get them t work on linux.eldiabolosk wrote:Like your idea. I am a newbie and I know nothing about relays. Sorry. I am Linux savvy. What USB sensors did you use with success? I need them for the same application as you.
Thanks for help.
mehran wrote:hi, i am heating engineer.
first off, its a great idea to try and replace a simple mechanical room stat with a computer controlled relay. coming from the heating side towards the electric side of things you can do much much more then just a simple on/off room stat with the pi.
i would think about how you would control the heating heat up rate and try and come up with other factors that would affect the heating.
for example. Honeywell use something called TPI (Time Proportional & Integra). basically if you break down the time in to 10 minute blocks then tpi would have heating on for 9 mins then off for 1 min. then as it gets closer to the set point(the temp you set) it would go 8on/2off, 7on/3off, 6on/4off.....1on/9off.
it would also would fire up even when it at the set point, too maintain the set point. if you could combine this with other external factors like the outside weather/ temp you could tune the heating to have a more aggressive ramp up in cold weather and a more gentle ramp up in mild weather.(or even pre-empt you feeling cold by switching the heating on even if its been set off)
there is loads and loads of stuff you could do just by being clever with the software.
replacing the a y/s plan holds even more. no guess what I will be doing with the pi ...
fruitloaf wrote:No its a conventional boiler with a water tank using 240V controls. If it was a combi boiler I'd probably just replace the thermostat and set the boiler to be on always at the controls and use the thermo to set on and off times.
Don't know anything about 0 volts I'm afraid.