(Sorry, Baidu is not on the picture here) Let me analyze it! A set of LM393 inputs has two phases, and four fine-tuning potentiometers are used for central voltage programming adjustment of LM393+/_ inputs. For example, if the input is connected to a positive potential, the input-input terminal can be connected to two fine-tuning potentiometers 10 ~ 30K, and the input+positive phase can also be connected to two 10 ~ 30K. If it is lower than 13V according to your requirements, it will automatically output 5V (connected to the three-terminal 7805 regulator), so the working voltage of the circuit design should be 6V ~ 9V for stability! Sampling 12.9V is only used as reference voltage. For example, in the voltage equivalent mode, the bias of these two potentiometers is adjusted to 12.9V as the sampling comparison voltage value, and the chip will automatically compare the difference of potential ratio to identify the output. Adjust the four potentiometers to make the positive and negative phases of LM393 lower than the critical point 12.9V. Under the condition that the reference voltage is12.9V, the voltage comparator of LM393 will be lower than 13V, and the output terminal of LM393 logic voltage comparator will output a high potential or a low level in response (the change of this high and low potential can be used as a starting voltage signal to drive a 5V power supply. High-power integrated built-in photoelectric thyristor switch can also be used instead of electromagnetic relay switch with mechanical opening and closing sound and low-speed response.
All principles are based on experiments! It is feasible in theory, but it must be verified in practice! Can be freely applied in the real world)
20 18—6— 18 GZ—jk