On Fri, 27 Nov 2020 20:28:26 +0000 (GMT), "Dave Liquorice"
wrote:

On Fri, 27 Nov 2020 15:59:50 +0000, T i m wrote:

I just had a look on eBay and there are quite a few choices of 2kW
opto coupled module that should be very easy to interface. An Arduino
Nano, a Dallas I2C external temperature probe and a few lines of code
and you should be able to do what you need.

KISS - solid state relay instead of PWM module. 1-Wire temperature
sensor and Arduino to generate the PWM to drive the relay directly
using a PID(*) control algorithm based on measured temp.

Well, apart from the relay instead of the SSR, it's pretty much the
same thing isn't it, well, other than the programming is more
complicated. ;-)

(*) Proportional Integral Derivative.
https://en.wikipedia.org/wiki/PID_controller

I was thinking you could (if it became necessary) to just
progressively reduce the PWM ratio every degree you got nearer the
target temp from a few away. Given the idea was the OP might get
better results using a lower powered and possibly oil filled rad, the
chances of any overshoot should be minimised in any case ... and he
was going to do the coding himself. ;-)

Cheers, T i m