I have a few sensors around the house where I collect some data and send it to an MQTT broker. I would like to use this data as temperature input for my house heater. My house heater has an input for a 4k7 thermistor and the interesting range is 3070 ohms (35 degrees C) to 7370 ohms (15 degrees C). I measure 5v between the two terminals on the heater where the thermistor should attach.
My approach to this was simple. Get a digital pot, in this case MCP41010 10k and set it to the apropriate value for the temperature I got from some sensor. The circuit is also simple: Arduino talks SPI to the pot and the heater is connected to the pots wiper and one terminal. I can measure the reisitance changing and I have no problem with the range I need. every step is around 39 ohms and that corresponds to around 0.16 degrees C change between steps. My problem is that when I connect this to the heater the heaters reported temperature fluctuates constantly. The heater can not get a stable reading I am guessing. My ohm meter reports steady resistance but I have no scope to measure the signal.
So my question to the greater internet knowledge is if I am going about this the right way? Is there another solution maybe using PWM, a transistor and a filter circuit? I feel my electronics skills are too limited and I need help! :confused: