Variable Voltage/Thermostat Control

[mpcaddy]

Hi,

I have a thermostat which is controls the heating using a variable amount of 12V. When the voltage drops below 5V the heating comes on, and lower the heating stays on longer.

I am wondering how best to hook the pi up to the heating instead of the thermostat so I can control the heating from the pi. I don't need to do any temperature monitoring as I already have plans on how to do that.

So basically the heating system supplies 12V DC to the thermostat and then the thermostat reduces that voltage. What would be the best way to use the Pi to control the voltage?

Thanks

[FLYFISH TECHNOLOGIES]

Hi,

I have a thermostat which is controls the heating using a variable amount of 12V

Is this "variable amount" pure analog voltage between 0 and 12V ?
Additionally, what is the current value here ? I guess that this is just a control signal, so the current is few mili amps or so ?

What would be the best way to use the Pi to control the voltage?

According to your explanation (and my understanding), the RasPi needs to switch just between two voltages: 12V to keep the heater off and something below 5V to turn it on...right ?


Best wishes, Ivan Zilic.

[mpcaddy]

Yes I think it's just an analog voltage from 0 to 12. Not sure about current atm I will measure when I get home.

It could just switch between them but if it could vary then that would be better as the heating comes on for different amounts of time dependant on how low the voltage is from my understanding of how it works eg
Currently when it's very cold compared to the thermostat value the hearing comes on for longer periods. If it's only slightly colder that the thermostat it comes on for short bursts.

If that makes sense?

[FLYFISH TECHNOLOGIES]

Hi,

Currently when it's very cold compared to the thermostat value the hearing comes on for longer periods. If it's only slightly colder that the thermostat it comes on for short bursts.

This is where temperature sensor fits in the story... but you want to keep it away...

Ok, so if you'd like to have a variable voltage, then (depends on required current), but digital potentiometer with I2C or SPI interface could be used without much effort. I've just quickly search for suitable element based on limited number of requirements known to me - AD5291 could be a candidate... There are some other elements with similar characteristics...


Best wishes, Ivan Zilic.