Difference between revisions of "Temperature Difference Sensor and Switch for Solar Water Circulation Pump"
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There is hysteresis because the copper pipes transfer heat and cool with a lag to the pump switching off/on. | There is hysteresis because the copper pipes transfer heat and cool with a lag to the pump switching off/on. | ||
Revision as of 09:08, 7 May 2022
ALL MY PROJECTS ARE HERE: https://opencircuits.com/index.php?title=User:Definitionofis
This is using two diodes to sense the temperature of the roof solar collector and the storage tank in the house. The diodes form a H-bridge which drifts +- through to -+ across the op amp inputs, depending on the temperature difference which varies the diodes' forward resistance. I have been running this for seventeen years with the diode on the roof touching the hot water outlet pipe.
File:Water temp difference sensor and-on-off-switch for solar-pump NoRelay.kicad sch
There is hysteresis because the copper pipes transfer heat and cool with a lag to the pump switching off/on. Also, my pump can run without harm, at low voltages, and slower speed. So a sharp slope in the switching speed versus temperature change is not needed for my pump. A steeper slope and instantaneous off/on for some other pump might need some further thought, like perhaps feedback-R6 should be much larger or omitted completely for more amplification. Experiment with it. Parts: https://www.futurlec.com/Transistors/IRF9532pr.shtml
Alternative configuration with a relay:
