Self built Hardware for thermic solar - 0 power on data timeout


I have built an own hardware to measure the energy production of my thermic solar system.
Actually i asume, the pump flow keeps constant, thus when the pump is switched on the esp8266 gets turned on equally. Then i am measuring the temperature difference with two sensors. With a little formula i can calculate the current power and i am transmitting the data to
My problem is, that because the power supply of the esp is directly connected to the pump relay, i cant know when the esp gets switched off, so i can transmit a 0.

I assumed that this is no problem, because, when the pump is switched off i have no energy flow and no interest in the Temperature difference. But actually emoncms keeps the last saved value over the entire timeout until the esp is switched back on again, where actually my power should be 0.

Has there anyone an idea, how i can get a 0 power when my esp8266 gets switched odd and times out?

her you can see the flat parts of the graph

Greetings, Markus

I don’t know the answer to your question, but I know others have enquired as to whether it’s possible to raise an event and take some action when you haven’t heard from a feed in some time. I’m not sure how that turned out, but it would probably satisfy your needs as well, if it were possible.

I too monitor my solar hotwater performance, although I don’t host the results on emoncms:
One obvious solution to your problem would be to power your monitor 24x7 rather than just when the circulation pump is running, which is what I do. I assume that’s not possible in your situation?