1 hour timer using LM122

As shown in the figure, this is a 1-hour timing circuit using LM122. The switching of the start, reset and midway stop of this circuit are all operated by switches. In the figure, S1 is the start timing. When the timer is started, pressing this switch again will not have any effect. S2 is the "off" switch located in the center. The timer can complete: charge-open circuit-discharge through the switch conversion. Since the charging is stopped midway, even if the timer setting time has not been reached, the charging position will return to the working state of the timer output circuit. When C is discharged and the voltage at the R/C terminal is zero, the discharge position waits for the start signal of S1. Even if the position is restored, the working state of the timer output circuit will not change. Therefore, when the timer is reset during operation, the state of the output circuit remains the same. At this moment, C starts charging again and changes to the starting point of the timer working time.