Hotwater heater temperature controler with Arduino LM35 & PID

I have a cheap tankless hotwater heater. The heater does not have a thermostat (I know, its cheap). I want to build a temperature controller with an Arduino, LM35 and a SSR. There is only one sensor on the output of the heater. Currently, I have code with an upper and lower limit; i.e., plus and minus 0.2 degrees Celsius of the required default temperature. I know there might be overshoots and undershoots hopefully not by much and that is why I have the range so narrow.

1- Would it be possible to implement PID for better control in the absence of any other hardware?
2- Just from an academic standpoint what other hardware would be required.

Any feedback would be appreciated.

Ray

your making it more complicated than it needs to be....there are ready made bolt on sensors that are pretty cheap that will do that job. "aquastat"

Hi,
Welcome to the forum.

I have a cheap tankless hotwater heater. The heater does not have a thermostat (I know, its cheap).

Can you post a link please, there are some pretty dodgy heaters on the inet.

There is only one sensor on the output of the heater

What is the sensor on the output?
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Can you please post a copy of your sketch, using code tags?
They are made with the </> icon in the reply Menu.
See section 7 http://forum.arduino.cc/index.php/topic,148850.0.html

Thanks.. Tom.. :slight_smile: