Instructables

how to make a thermo regulator?

i want to heat water between 20c -40c


frollard1 year ago
do you mean 20-to-40 degrees Celsius or 20 to -40 Celsius?

Same tech will do it but various components may need to be switched if its below freezing.

What you need is a feedback loop that checks the temperature and changes the output of the (presumably heater) to suit the temperature requirements. There are a million ways to do it, the simplest being a thermostat connected to a heater. It can be active, passive, use analog components or go digital with a microcontroller.
Can't "heat" water to -40C, there is a slight problem.....
solid water can exist below -40C, where it can then be heated to -40 and above.

English has a way of adding extra words (like ice)...but water is still water when its ice or steam.